Combined Industrial Wastewater Treatment in Constructed Wetland Systems Containing Emergent Plants and Algae

Tesis de Máster , 2015 , 82 Páginas

Ciencias de la Tierra / Geografía - Geografía física, geomorfología, estudios ambientales

The objective of this study is to access the effectiveness of integrated biological treatment systems including Internal Circulation bioreactor (IC) and constructed wetlands (CWs) containing either macrophytes or algal biomass for treating industrial wastewater. Anaerobic reactor alone was able to reduce COD (52%), turbidity (89%), EC (24%). Bioreactor was not efficient in meeting NEQs of Pakistan. So, post treatment of Anaerobic bioreactor effluents was carried out in CWs containing macrophytes (Arundo donax and Eichhornia crassipes) reduce COD (89%), turbidity (99%).

Wetlands containing algal biomass were not effective in treating majority of water quality parameters. Inhibition of algal biomass was observed due to physicochemical characteristics of wastewater. The integrated treatment system consisting of IC bioreactor and macrophytes is a more suitable option to treat industrial wastewater.

Content

Chapter 1 Introduction
1.1 Need for Low Cost Natural Treatment System
1.2 Anaerobic Digestion
1.2.1 Mechanism of Anaerobic Digestion
1.3 Phytoremediation
1.3.1 Constructed Wetlands (CWs)
1.4 Pollutant Types and Removal Mechanisms
1.5 Role of Plants in CW Treatments
1.6 Types of vegetation used in CWs
1.6.1 Eichhornia crassipes
1.6.2 Arundo donax
1.6.3 Algae
1.7 Benefits
1.8 Issues in practical application of CW
1.9 Statement of the Problem
1.10 Purpose of the Study
1.11 Objectives

Chapter 2 Materials and Methods
2.1 Study Site
2.1.1 Hattar Industrial Estate (HIE)
2.2 Collection of wastewater sample
2.2.1 Sample characterization
2.3 Collection of Algae, Plants and Sludge
2.4 Experimental Design
2.4.1 Construction of CW
2.4.2 CW Layering
2.4.3 CW Operation
2.4.4 Anaerobic Bioreactor
2.4.5 Experimental Setup of IC bioreactor
2.4.6 Post treatment
2.5 Analytical procedures
2.5.1 COD
2.5.2 Electrical Conductivity
2.5.3 pH
2.5.4 Turbidity
2.5.5 Heavy metals
2.5.6 Phosphates (PO4-)
2.5.7 Sulphates
2.5.8 Nitrates

Chapter 3 Results
3.1 pH change in IC Bioreactor
3.2 Electrical conductivity trend in IC bioreactor and CWs
3.3 Reduction in Turbidity
3.4 Reduction of COD
3.5 Nickel reduction
3.6 Cadmium Reduction
3.7 Copper Reduction
3.8 Zinc Reduction
3.9 Lead Reduction
3.10 Phosphate reduction
3.11 Nitrate Reduction
3.12 Sulphates Reduction

Chapter 4 Discussion
4.1 Discussion
4.2 Post treatment of IC bioreactor effluent by mixed culture Plants and Algae
4.3 Algae
Conclusions
Recommendations

Chapter 5 References

List of Tables

1.1 Degradation steps in IC Bioreactor

1.2 Pollutant removal mechanisms

3.1 Metal removal by IC bioreactor and Post treatment

List of Figures

1.1 Classification of CWs and physical designs for wastewater treatment

2.1 Flow chart of Anaerobic and Post Treatment

2.2 Constructed wetlands with mix culture plants

2.3 Schematic diagram of (IC) bioreactor

3.1 Change in pH change by IC Bioreactor

3.2 pH Change in Mixed culture of Plants

3.3 Change in pH by Mixed Culture Algae

3.4 Electrical Conductivity Reduction by IC Bioreactor

3.5 EC change by Mixed Culture of Plants

3.6 Change in EC by mixed culture of algae

3.7 Reduction in Turbidity by IC Bioreactor

3.8 Turbidity Reduction by Mixed Culture Plants

3.9 Change in turbidity by Mixed Culture Algae

3.10 Reduction in COD by IC Bioreactor

3.11 COD Reduction by Mixed Culture Plants

3.12 COD Reduction by Mixed Culture Algae

3.13 Nickle Reduction by IC Bioreactor

3.14 Nickle Reduction by Mixed Culture Plants

3.15 Nickle Reduction by Mixed Culture Algae

3.16 Comparison of Nickle Concentration Reduction

3.17 Cadmium Reduction by IC Bioreactor

3.18 Cadmium Reduction by Mixed Culture Plants

3.19 Cadmium Reduction by Mixed Culture Algae

3.20 Comparison of Cadmium Concentration Reduction

3.21 Copper reduction by IC Bioreactor

3.22 Cadmium Reduction by Mixed Culture Plants

3.23 Cadmium Reduction by Mixed Culture Algae

3.24 Comparison of Copper Reduction

3.25 Zinc Reduction by IC Bioreactor

3.26 Zinc Reduction by Mixed Culture Plants

3.27 Zinc Reduction by Mixed Culture Algae

3.28 Comparison of Zinc Reduction

3.29 Lead Reduction by IC Bioreactor

3.30 Lead Reduction by Mixed Culture Plants

3.31 Lead Reduction by Mixed Culture Algae

3.32 Comparison of Lead Reduction

3.33 Phosphate Reduction by IC Bioreactor

3.34 Phosphate Reduction by Mixed Culture Plants

3.35 Phosphate Reduction by Mixed Culture Algae

3.36 Comparison of Phosphate Reduction

3.37 Nitrate Reduction by IC Bioreactor

3.38 Nitrate Reduction by Mixed Culture Plants

3.39 Nitrate Reduction by Mixed Culture Algae

3.40 Comparison of Nitrate Reduction

3.41 Sulphate Reduction by IC Bioreactor

3.42 Sulphate Reduction by Mixed Culture Plants

3.43 Sulphate Reduction by Mixed Culture Algae

3.44 Comparison of Sulphate Reduction

LIST OF APPENDICES

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Chapter 1 Introduction

Water is crucial natural constituent for all aspects of life, the defining feature of our planet (Corcoron et al., 2010). It has unique nature due to its various properties. It is colorless, odorless and tasteless reserve. Water has various applications like cleaning, and washing, it is widely used in agricultural and Industrial sector in various manufacturing processes. Human body constitutes 70% of water. In short, life cannot exist without water. Water is the basic reserve for the development of human society, as well as for the ecosystems stability (Oki and Kanae, 2006; Vorosmarty et al., 2010). Water is a very valuable and vital commodity that we consume, waste it, discard it, pollute it, poison it, and then persistently change the natural and urban hydrological cycle by ignoring its consequences: “Too many peoples, too many little water in the wrong places and in the wrong amounts. the human population is burgeoning, but water demand is increasing twice as fast” (De Villiers, 2000).

Presently, we are facing two major issues which are environmental pollution and energy crises. It is due to rapid increase in population and industrialization resulting in massive amount of wastewater that is discharge into the environment. Wastewater is a combination of pure water with large number of chemicals (including organic and inorganic) and heavy metals which can be produced from domestic, industrial and commercial activities, in addition to storm water, surface water and ground water (Dixit et al., 2011). According to standard regulations, wastewater which is being generated by several industrial processes must be treated before discharge into the environment. The rapid growth in industrialization provokes environmental pollution and also utilizing natural reserves resulting to their depletion. (Suzuki et al., 2002). The conventional treatment processes are energy consuming. So basic necessity is to find out alternate approaches for wastewater treatment that not only treat wastewater but also recover energy (Kim et al., 2000; Logan et al., 2002).

1.1 Need for Low Cost Natural Treatment System

Due to the recent economic conditions and energy shortage in several developed and developing countries, here is a necessity to implement low cost and efficient natural wastewater treatment system. Anaerobic digesters, constructed wetlands, oxidation ponds, facultative ponds, lagoons, anaerobic ponds, terrestrial systems and vermicomposting. CWs are the wastewater treatment system that needs low energy input, low working as well as maintenance cost and in turns CWs generates low sludge output (Mahmood et al., 2013). Due to the threat of the entry of chemicals into 2 wastewater it must be treated before the final discharge. Many physical, chemical and biological methods have been established for the treatment of wastewater. It was described that biological treatment methods are suitable for wastewater treatment, Phytoremediation is one of effective biological method for wastewater treatment (Roongtanakiat et al., 2007). For developing nations there is a need for different kinds of procedures for water bodies improvement and dealing with domestic and industrial wastewater in rural areas have been serious concern. The use of CWs has significantly extended from tertiary and secondary domestic sewage treatment to the treatment of agricultural runoffs, industrial discharges, landfill leachate, urban and high way run off (Wu et al., 2013). The CWs are emerging technology which is used for the treatment of many types of wastewaters. The natural wetland system uses mostly natural energy, requires low construction and operational costs, and so is energetically sustainable. But, this postulation is not true for CWs where some energy, input from human source is also mandatory (Mahmood et al., 2013).

1.2 Anaerobic Digestion

Anaerobic degradation or digestion is natural process which comprises the breakdown of organic and inorganic matter through various activities performed by wide range of microbial consortia in the absence of oxygen. Mainly this biological processes are used to remove various pollutants, in wastewater treatment. Now a day’s Anaerobic digestion (AD) is a suitable option for waste treatment approaches in which both energy recovery and pollution control can be accomplished (Mittal., 2006; Wijetunga et al., 2010). The principle of anaerobic digestion is to employ the anaerobic microbial consortia (biomass) to convert organic matter (pollutants) or COD (chemical oxygen demand) into biogas (methane) in the absence of oxygen (Abdelgadir et al., 2014). First anaerobic digester was developed by a leper colony in (1859) Bombay, India (Meynell,1976). In 1895 this technology was used for the generation of gas by developing septic tank in Exeter, England, represents the First generation of AD. In 1970 (UASB) process was developed by Dr. Gatze Lettinga and colleagues to epitomize the second generation of AB (Lettinga et al., 1980; Kato et al., 1994). The third generation of AD was built on the foundation of the second generation such as expanded granular sludge bed (EGSB) and internal circulation (IC) reactor (Seghezzo et al.,1998).

(Lu and Liao 2010) developed ideas and design approaches for the IC reactor. Internal circulation (IC) anaerobic reactors validate the principle of upflow reactor, consist of two chambers where reactions are done with a tri-phase separator in the upper part of each chamber, namely, the influent pipe and the returned pipe (Miao, et al., 2013). (Deng et al., 2006) IC reactor was used to treat raw swine wastewater. Also treat brewery wastewater (Miao, et al., 2013). According to many researches anaerobic digesters are most effective, the IC reactor is extensively used to treat various types of industrial wastewater due to its high loading rate (OLR), considerable feasibility, high resistance, and cost effective, as compared with the second generation up flow anaerobic sludge blanket (UASB) reactors (Deng et al., 2006; Lu and Siao,2010).

1.2.1 Mechanism of Anaerobic Digestion

Hydrolysis is the first stage, where bacteria changes the organic pollutants into monomers and polymers. In hydrolysis reaction where organic waste is broken down into a simple sugar/glucose. Second stage is Acidogenesis, where acidogenic bacteria transform the products of the first reaction into short chain volatile acids, ketones, alcohols, hydrogen and carbon dioxide. The hydrogen, carbon dioxide and acetic acid are utilized directly by the methanogenic bacteria in the final stage of degradation process. Third stage which is acetogenesis, the byproducts of acidogenesis process, (propionic acid, butyric acid and alcohols) that are transformed by acetogenic bacteria into hydrogen, carbon dioxide and acetic acid (Mata- alvarer, 2003). During the final stage of degradation process, methanogens changes the hydrogen and acetic acid into methane gas and carbon dioxide and then waste stabilization is accomplished (Miah et al., 2005).

Table 1.1: Degradation steps in IC Bioreactor

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1.3 Phytoremediation

Phytoremediation is considered to be a possible biological treatment method for the removal of pollutants present in wastewater and documented as a better green remediation technology. Nowadays the focus is to look for a sustainable approach in developing wastewater treatment capability (Rezania et al., 2015). Phytoremediation techniques use any one of the sixmechanisms such as phytoaccumulation/phytoextraction, phytotransformation, phytostabilization, phytovolatilization, phytostimulation, and rhizofiltration (Rahman and Hasegawa, 2011; Erakhrumen and Agbontalor, 2007). The main idea of this procedure is based on the using of emergent plants and microorganisms in the same process as to remove the pollutants from desired environment.

1.3.1 Constructed Wetlands (CWs)

CWs are designed to employee the natural processes involving wetland plants, soils, and microbes that helps in treating wastewater (Hayder et al., 2015). CW are working as same processes that occur in natural wetlands, but organize within a more controlled environment, used to treat wastewater, while others CW have been employed with multiple-use objectives in mind, such as using treated wastewater effluent as a water source for the creation and re-establishment of wetland territory for flora and fauna use and for reuse in farming or environmental improvement (Vymazal, 2014).

1.3.1.1 Types of Constructed Wetlands

CWs for wastewater treatment are characterized according to the various design parameters and many important criteria’s such as, hydrology (open water-surface flow and sub-surface flow), type of vegetation (emergent, submerged, free- floating, and floating-leaved) and flow regime in sub-surface wetlands (horizontal and vertical) (Vymazal, 2005, 2008).

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Figure 1.1: Classification of CWs and physical designs for wastewater treatment

1.3.1.2 Constructed Wetlands with Free Water Surface

Surface flow CWs also known as free water surface constructed wetlands, (FWS CW) which contains basins or conduits, with suitable substrates that helps to support the vegetation, water with moderately shallow depth flowing through the system. FWS CW are excavated with shallow water depth, low water flow velocity, and existence of the plants debris and litter control water flow and, especially in long narrow conduits, to confirm mass-flow conditions (Reed et al.,1988).

1.3.1.3 Subsurface Flow Constructed Wetland

In SSF systems, roots of emergent plants are embedded in a porous media such as gravels or aggregates through which water flows and treatment can be achieved. Subsurface Flow (SSF) systems are classified into horizontal flow SSF and vertical flow SSF. The difference between HSSF and VSSF system is not only in the flow regime of water but also its growth conditions (anaerobic and aerobic conditions) through which plants can be grow. In HSSF the flow regime of water is continuous where as in VSSF system flow regime of water is discontinuous (Mahmood et al., 2013). (Kivaisi, 2001). CWs can meritoriously remove suspended solids (SS), organic pollutants inorganic pollutants and nutrients from all types of wastewater (Vymazal, 2013; Kadlec, 2008; Peng et al., 2014).

1.4 Pollutant Types and Removal Mechanisms

FWS CWs are, mostly planted with emergent plants and working as land-intensive biological treatment systems. The suspended solids (SS) are remove through different mechanisms such as, sedimentation, filtration, aggregation and surface adhesion. The heaviest particles will primarily settle out in the inlet open water zone, lighter particles will settle down after flowing into wetland plants. CWs plants helps to stimulates and improve sedimentation by reducing water column mixing and re-circulation of particles from the sediment surface. FWS CW are used for wastewater treatment naturally have aerated zones, mostly near the water surface due to atmospheric diffusion, and anoxic and anaerobic conditions within and near the sediments. Decaying of biomass helps to provides a carbon content for denitrification, but biomass decay also competes with nitrification for oxygen source (Kadlec and Knight, 1996).

Settleable organics are settled at the bottom of FWSCW are promptly removed under quiescent conditions through deposition and filtration process. Attached and suspended microbial community in FWSCW is accountable for the removal of soluble organic compounds which are degraded under aerobic conditions in the presence of heterotrophic bacteria (Vymazal et al., 1998), and under anaerobic conditions in the presence of facultative or obligate heterotrophic bacteria (Cooper et al., 1996). In wetland water column oxygen is provided through diffusion process where air and water interfaces by the photosynthetic activity of plants in the water column, namely periphyton and algae (Kadlec et al., 2000).

In FWS CWs with floating vegetation, these plants entirely cover the water surface, so it prevents light penetration into the water column. Therefore, the algal growth is restricted, as a result anoxic/anaerobic conditions may prevail due to low photosynthetic activity of algae. Nitrogen is successfully removed in FWS CWs through nitrification/denitrification. In aerobic zones ammonia is oxidized through nitrifying bacteria, and in anoxic zones nitrate is converted to free nitrogen or nitrous oxide through denitrifying bacteria. Volatilization of pollutants is possible in FWS CWs through emergent and submerged plants. Higher growth of Plankton, periphyton algae, higher pH values, and ammonia loss increases in FWS CWs during day time, when photosynthetic activity increases. FWS CWs are helpful for sustainable removal of phosphorus at relatively low level and this is slow process. Removal of Phosphorus through different mechanisms such as, adsorption, absorption, complexation and precipitation. (Brix,1987; Cooper et al., 1996).

1.5 Role of Plants in CW Treatments

Different scientists have shown that a wetland system with vegetation has a higher efficiency of pollutant removal than without plants (Wu et al., 2013). The removal capabilities of well-developed vegetation could be explained by: The rhizosphere connected to a vegetation in CWs through active oxygenic photosynthesis will allow the transfer of a certain amount of oxygen to the surrounding area of the roots. In the root system, where oxidation reduction potential and nitrification rate are both higher due to existence of large number of bacteria than the area without vegetation, and each plant root system is considered as a mini aerobic biological treatment system. Uptake into the plants.

The treatment of organic pollutants by plants may involve four mechanisms (Mahmood et al., 2013).

In plant tissues detoxification can be done through direct uptake, accumulation, and metabolism of contaminants. Volatile organic hydrocarbons are transpired through leaves process called avoidance. Discharge of exudates from the roots which in turns stimulate microbial activity and biochemical transformations, this process is known as chelation. The presence of mycorrhizal fungi and groups of microbes which are associated with the surface of root which can boost the mineralization of contaminants in rhizosphere.

Different studies have been made about the use of wetland technology for treating different types of wastewater which are generated from different sources such as domestic water, municipal water, coffee processing wastewater, fish farm water, agricultural runoff, Coke plant effluent, Refinery effluents, Pulp and paper, Tannery effluents, Pharmaceuticals, Laundry, Organic chemistry, Textile, Distillery, Winery, Brewery, Soft drink, Sugar mill, Vegetable and food processing, Meat processing. (Vymazal, 2014). Constructed wetlands can eliminate most of pollutants like pathogens, nutrients, organic and inorganic pollutants, protect the health of community to prevent spread of waterborne diseases.

Table 1.2: Pollutant Removal Mechanism

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1.6 Types of vegetation used in CWs

There are four kinds of vegetation that’s are used in CWs, which are growing on different forms of CWs.

1.6.1 Eichhornia crassipes

Eichhornia crassipes commonly known as water hyacinth and introduced in environment as an invasive aquatic species and gained more attention as free floating macrophyte. It belongs to family Pontederiaceae, has four species including E. azurea, E. crassipes, E. diversifolia and E. paniculata have been discovered so far, native to Brazil far (Verma et al., 2003; Tellez et al., 2008). Among all these aforementioned E. crassipes has widely acclimatized in many countries like; Europe, Africa, Asia and North America (Shanab et al., 2010). For several years, E.crassipes has high attractive appearance by humans (Gopal, 1987). In Pakistan this macrophytic weed is mostly found in Swabi, Taxila, Abbotabad (Fawad et al., 2013; Hussain et al., 2010; Malik et al., 2009; Ghosh and Singh, 2005; Mishra and Tripathi, 2009).

The plant body of E.crassipes of creeping horizontal stem, rhizome leaves, fruit clusters, fibrous tissues, fibrous roots and soft leaves. Average growth is from 0.4 m up to 1 m height. E.crassipes has 6 to 10 lily-like flowers, stems and leaves are made from air-filled tissues which allows the plant to float on water. This plant has high potential for; biomass productivity, store high protein and energy content in their cell. It has many applications like bio-fuel production, biomass and energy, waste water treatment, compost and fertilizer, animal feed and for making furniture (Rezania et al., 2013).

High biomass mass productivity, floating habitat, Huge potential for the removal of organic and inorganic pollutants (Priya and Selvan, 2014; Yan et al., 2016). Temperature tolerance from 10°C up to 40 °C (Gettys et al., 2009; Malik 2007), shows optimum growth temperature 25 -27.5 °C (Wilson et al., 2000), Seed can survive up to 20 years, Optimum PH 6-8 °C (Gopal, 1987; Patel, 2012), Water salinity ≤5mg/L (DeCasabianca et al., 1995), Grow even in low concentration of nutrients (Zhou et al., 2012), Lost operational cost , Renewability. Water hyacinth were helpful in treating industrial wastewater, found maximum removal efficiency of heavy metals in 10th day experiment such as, Zn, Cu, Cd, Cr. Roots was found to be as high accumulator (Yapoga et al., 2013). Mix culture of water hycainth and salvina natans was used for the treatment of municipal wastewater, and helpful for the removal of organic and inorganic pollutants such as 84.5 % BOD, 83.2% COD, 26.6 % NO3, 56.6% PO4 (Kumari and Tripathi, 2014).

1.6.2 Arundo donax

It is a robust tall perennial rhizomatous grass belongs to family “Poaceae”, genus “Arundo”, which is native to Eastern Asia (Indian sub-continent) and Mediterranean Basin, but presently this specie is well distributed worldwide (Polunin and Huxley, 1987). It is found in Asia, Southern Europe, North Africa and the Middle East for thousands of years with local names of ‘‘Nurr”, ‘‘Nurru” or ‘‘Nurro”. But in Pakistan it is mostly found in Abbottabad, Peshawar and Gujranwala (Shaheen et al., 2016, Mirza et al., 2010; Kausar et al., 2012).

It does not propagate through seeds, but it can only spread vegetatively through their rhizome (Perdue, 1958). It is aquatic plant which is growing along lakes, streams, drains and other moist places; it acquires cane like stem having length of 2–3 cm in diameter, has alternative arrangement of leaves, having length of 30–60 cm and wide up to 2–6 cm, narrow tips and hairy cluster at the base. As terrestrial plant it grows up to height of 8 m. Shows highest growth under optimum conditions it can grow up to 5 cm day. (Mirza et al., 2010).

A.donax L. can grow in different habitat with vast ranges of pH, salinity, drought and trace metals without developing stress conditions. A.donax L. can easily habituate to different ecological conditions and grow in all types of soils. (Polunin and Huxley, 1987). It has high metals tolerance and bioaccumulation through the process of phytoremediation, it has high absorbing capacity against various pollutants such as metals which cannot be easily biodegraded (Papazoglou et al. 2007; Mirza et al., 2011; Nsanganwimana et al., 2014). In 5,000 B.C where the Egyptians used A.donax L leaves as lining for underground grain storage, mummies were enfolded with Arundo donax leaves, but In recent years Arundo donax has been commercially used for musical instruments and horticultural purposes, (garden fences and trellises)(Miles et al., 1993). Medicinal uses include the rhizome or rootstock was used for dropsy, cancer, condylomata, indurations of breast, root infusion was used as antigalactagogue, depurative, diaphoretic, diuretic, emollient, hypertensive and sudorific, pertussis and cystitis (Bandaranayake, 2002; Temiz et al., 2013), as haemostatic in toothache (Safa et al., 2003). Through the process of fermentation

A.donax can be used for the generation of biogas and bioethanol, also used as direct biomass combustion. In industries it can be used for production of chemical compounds (Corno et al., 2014). A.donax can be used for the removal of different kinds of trace metals from toxic environment through the process of phtoremediation such as; Ar, Se, Cu, Ni, Zn, and Cd (Mirza et al., 2010; Bonanno, 2012; Sabeen et al., 2013; El-Ramady et al., 2015; Shaheen et al ., 2016 ).

1.6.3 Algae

Algae are unicellular or multicellular, photosynthetic but lake true leaves, stems and roots. Their habitat is fresh water and moist areas. Algae have a great value to life on earth. Algae are of incredible importance to life on earth. In all ecosystems these are act as primary producers, they play a vigorous role in food chains. Algae are habitually contributing fresh oxygen to the atmosphere, whereas animals act as contaminat agent by adding Carbon dioxide. They directly or indirectly assist as food of many aquatic animals, like fish, which in turns have great importance to human community. Their luxuriant growth tells about the taste and odor of water, which make it unfit for drinking. Physico-chemical features play an crucial role in the dispersal of Algal species and distribution of fish and fauna among them (Ali et al., 2010). The concept of using microalgae for wastewater treatment established in the 1950s in California by William Oswald (Oswald and Gotaas, 1957; Oswald, 1963). The use of macro algae or microalgae for effective removal or biotransformation of contaminants, including nutrients (Phosphorus,Sulphate,Nitrates) and xenobiotics from wastewater and CO2 from waste air called phycoremediation (Olguin, 2003). Benefits of using algae for wastewater treatment include: has low operational cost, a food source for aquatic organisms, avoidance of the sludge handling problem, and direct release of oxygenated effluent water into the water bodies (Choi and Lee, 2012; wang et al., 2013). Moreover, nutrients are not only removed from the wastewater, but can also be captured and returned to the terrestrial habitate as agricultural fertilizer, CO2 fixation, that contributes to mitigating greenhouse gases (Wang et al., 2008; Van den Ende et al., 2012). Microalgae are able to perform a dual function of bioremediation of wastewater as well as generating algal biomass for biofuel generation (Mulbry et al., 2008; Fathi et al., 2008). Usually, algae isolated from a wastewater treatment plant site or real water body can adapt to the practical conditions better and show higher efficiency of inorganic nutrient removal (Xin et al., 2010). Wastewater treatment in Waste Stabilization Ponds (WSPs) is "green treatment" accomplished through the mutualistic growth of microalgae and heterotrophic bacteria. The by product of algae is oxygen production through the process of photosynthesis, then by product (oxygen) is used through the bacteria, they helps to oxidize th organic matter which is present in wastewater and produce carbon dioxide which is fixed into cell (Aslan and Kapdan, 2006; Brito et al., 2007; Hodaifa et al., 2010 a, b; Sharma and Khan 2013).

1.7 Benefits

CW has many benefits including: eco-friendly, simple and easy, high economic value, operative and ecologically sound approach (Roongtanakiat et al., 2007) which entail lesser land area (Lu, 2009). CWs also helps to improve air quality that in turns prevention of climate changes by lesser production of carbon dioxide, hydrological functions and bio- methylation (Azaizeh et al., 2003).

1.8 Issues in practical application of CW

According to (Huang et al., 2013) many hindrances were found in the practical application of CWs e. g. they are susceptible to climatic conditions and temperature, their substrates are easily saturated and plugged, exaggerated through plant species, dwelled large areas, irrational management, non-standard design. Up to certain extent these issues stimulate the efficiency of constructed wetlands in wastewater treatment, shorten the life of the constructed wetland, and hamper the application of artificial wetland (Huang et al., 2013).

1.9 Statement of the Problem

Previous studies did not highlight the role of algae in the wastewater treatment along the macrophytes (which have been well documented). In this background the present investigation should be carried out to elucidate the contribution of algae in wetlands.

1.10 Purpose of the Study

The purpose of this study is to find a cost-effective technology for combined waste water treatment by using different plants and algae in CWs. The lab scale information obtained from the current research will help to design CWs at large scale.

1.11 Objectives

To find out the potential of emergent plant species and algae to treat the pollutants from wastewater.

Chapter 2 Materials and Methods

2.1 Study Site

Wastewater samples were collected from Hattar Industrial Estate.

2.1.1 Hattar Industrial Estate (HIE)

Hattar Industrial Estate (HIE) is a new estate which has been developed in Pakistan for industrial discharges according to appropriate planning and management. The government of NWFP accepted HIE in 1985 in Haripur district. This industrialized area was distributed in different phases. In HIE 700 acres were assigned to major industries such as ghee industry, fertilizer industry, chemical industries, textile industry and pharmaceuticals industry. HIE has large number of surface drains, all industries and city sewage are discharging their effluents in their neighboring drain. All these effluents are ultimately moves towards wider drain nullah known as “Jaricus” which is located in Dingi village. The collective discharges of industries from “Jaricus” are laterally falls into the Haro River (Sial et al., 2006).

Due to lack of strictness to environmental planning guidelines in Pakistan, industries discharges their solid and liquid wastes in neighboring sites, nullahs, and streams that mixed with groundwater, increasing HMs concentration than concentration recommended by WHO and cross NEQS limits (Gulfraz et al., 2002). Due to water scarcity farmers near HIE are using industrial effluents for growing vegetables and cereal crops. The effluents discharged by different industries contain a huge amount of pollutants (organic and inorganic) like pH, conductivity, hardness, alkalinity, COD, TSS, nitrates, nitrites, cations (Na+, K+, Ca2+ and Mg2+) and anions (Cl−, CO32−, HCO3−, SO42−). These effluents from HIE industries also contain HMs and trace metals including chromium, cadmium, copper, lead, nickel, zinc, cobalt, magnesium, iron and arsenic.

2.2 Collection of wastewater sample

Samples that were used to study “removal” efficiency of organic and inorganic pollutants from wastewater through Internal Circulation Bioreactor and then post treated through mixed culture of emergent plants and algae. Grab sampling technique was applied for collection of industrial wastewater. The industrial wastewater was collected from “Jaricas Area” a combined drain at Hattar Industrial Estate, Pakistan. For sample collection pre sterilized cane was used and stored wastewater.

2.2.1 Sample characterization

After sample collection all physicochemical parameters of wastewater were analyzed according to APHA (2005) in Environmental Engineering lab (A224) within 24 hours.

- Physicochemical parameters included:
- Colour
- Turbidity
- Odour
- pH
- COD
- PO4
- SO4
- NO3
- Electrical Conductivity
- Heavy Metals

2.3 Collection of Algae, Plants and Sludge

The sludge was collected from the municipal committee of Abbottabad in a cane. Two fresh and young emergent plant species were brought from different locations. As (a) shows Echornia crassipes was brought from Charsadda, (b) shows Giant reed was brought from Haripur, and (c) shows mixed culture Algae was brought from Mirpur Abbottabad. All these plants species were washed properly with distilled water for the removal of dirt and soil particles.

Due to copyright reasons, the figures (a), (b) and (c) were removed for the publication

2.4 Experimental Design

2.4.1 Construction of CW

The lab scale experimental constructed wetlands consisted of three rectangular basins made of glass, had and area of 120×90×40 cm.

2.4.2 CW Layering

The wetlands were layered with coarse gravel, and sand. For the removal of pollutants gravel and sand were separately rinsed by HCl solution (The HCl solution was made by dissolving 20 ml of 37% HCl in 1 litre of water and it was then further diluted), and then washed three times with tap water. After rinsing gravel and sand were dried in sunlight for 2 days After drying the wetlands were layered simultaneously. The first layer of gravel was about 3 cm, second layer of sand was about 5 cm and third layer of gravel was about 1 cm respectively

2.4.3 CW Operation

Two CW were used. In wetland A mixed culture of emergent plant species was grown by maintaining aerobic conditions in it. In wetland B mixed culture of algae were grown. Whole treatment process consisted of anaerobic treatment by internal circulation bioreactor and post-treatment of industrial wastewater by using macrophytes and algal species.

2.4.4 Anaerobic Bioreactor

In the present study Internal Circulation bioreactor was used for the treatment of industrial waste water sample which was brought from “Jaricus”.

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Fig 2.3: Schematic diagram of Anaerobic (IC) bioreactor

2.4.5 Experimental Setup of IC bioreactor

A laboratory-scale IC bioreactor was set up for the experiment which was taken from CIIT Abbottabad, made from Plexiglas having the diameter of 95 mm, 676 mm height with the total volume of 1.8 L (working volume 1.3 L). A schematic diagram of the process is shown in (Figure: 2.3)

Then sludge which was brought from municipal committee of Abbottabad, were poured with tap water into the IC bioreactor, and left the IC bioreactor for SRT (sludge retention time) of 48 hours.

Industrial Wastewater was fed through peristaltic pump into the IC bioreactor at 0.5 rpm (Rotation Per Minute) for 12 hours HRT (Hydraullic Retention Time) that treated 1800 ml of wastewater. After 12 hours anaerobic treatment was done and effluent was collected in the effluent tank. Physico-chemical parameters of wastewater were analyzed before and after anaerobic treatment. Then this pretreatment water was collected in a storage tank, then placed in CW for post treatment analysis.

2.4.6 Post treatment

In wetland A, 25 liters of industrial wastewater was added and then mixed culture of emergent plant species of E.crassipes and A.donax by equally weighed 400g each, total weight of 800g were planted in it. In wetland B, 800g of algae were grow and then add 25 liters of wastewater was added for 20 days and treated it.

2.5 Analytical procedures

The water parameters like pH, electrical conductivity and turbidity were analyzed on daily basis, where as other parameter like COD was analyzed after three days, Metals, Nitrates, Phosphates, Sulphates were analyzed weekly.

2.5.1 COD

The Chemical oxygen demand was determined by using closed reflux colorimetric method using digester (HACH - LTG 082.99.40001) according to standard method (APHA, 2005). Potassium dichromate and Sulphuric acid were used as reagents. Firstly, 1.5 ml of potassium dichromate solution was added in a COD vial. Secondly, 3.5 ml of sulphuric acid solution were taken in vial. Then 2.5 ml of sample was added in vial. After vial preparation it was then placed in COD digester at 150 °C for 2 hours. After that reading was checked on COD meter.

2.5.2 Electrical Conductivity

EC is also known as specific conductance of ions and measured in µS/cm. Electrical conductivity of the samples was analyzed by using conductivity meter (Wagtech International ,serial number : 1497311)

2.5.3 pH

The pH of the wastewater samples was examined by using a digital pH meter (ADWA, Model no.: AD 1030). pH meter was calibrated by using buffer solution then readings were taken.

2.5.4 Turbidity

Turbidity is the amount of cloudiness in the water. Samples turbidity was determined by turbidometer (Eutech, TN-100). Its unit is NTU (Nephelometric Turbidity Units).

2.5.5 Heavy metals

Atomic absorption spectroscopy (Perkin Elmer Model 920) was used for heavy metals detection. First of all, samples were filtered through filter paper. Then this filter sample was transferred into bottles. Standard were made by using blank samples (de-ionized water) and the standard solution of the necessary heavy metals. e.g; for each standard firstly the standard solution was diluted in 100 ml de-ionized water and then the standard was further diluted according to the formula (M1V1=M2V2). Then the filter samples were analyzed on atomic absorption spectrophotometer by using the standards and use the blank first.

2.5.6 Phosphates (PO4-)

By using UV-VIS Spectrophotometer (IRMeCO UV-Vis, U2020) phosphate content were determined. Firstly, 10 ml of water sample was taken and then added 1 ml of aluminum molybdate solution and 0.4 ml of stannous chloride SnCl2.H2O, mixed it and blue color was developed, after that readings were recorded at 680 nm.

2.5.7 Sulphates

By using UV-VIS Spectrophotometer (IRMeCO UV-Vis, U2020) sulphates content were determined. Firstly, 10 ml of filtered sample was taken and added 10 ml of deionized water in it, then 5 ml of conditioning reagent was added and mixed it. After that readings were recorded at 420 nm.

2.5.8 Nitrates

By using UV-VIS Spectrophotometer (IRMeCO UV-Vis, U2020) nitrates content were determined. Firstly, 20 ml of filtered sample was taken and added 1 ml of 0.1 NHCl, and then mixed well. After that sample was poured in cuvette, readings were recorded at 220 nm.

Chapter 3 Results

3.1 pH change in IC Bioreactor

pH change is depicted in (Fig 3.1) with respect to three weeks of operational days. pH of “Jarikas” wastewater ranges between 7.2 to 8.3 during all operational days which was 3 weeks. IC bioreactor was daily fed with 1.8 L of wastewater for 12 hrs HRT. After IC bioreactor treatment maximum pH ranges between 7.5 to 8.7. Similarly, there was little variation was found in pH of wastewater (Fig 3.1). pH changes due to activities performed by microbial consortia present in Anaerobic bioreactor, which helps to degrade the pollutants from wastewater. Effluent of AD was further treated by post treatment. Initially, pH of influent of mixed culture plant and mixed culture of algae was 8.4 with the passage of time it was fluctuated. pH value of mixed culture plants effluent ranges from 8 to 8.8 and effluent of mixed culture algae was 7.7 up to 8.9 shown in (Fig 3.2) and (Fig 3.3).

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Fig 3.1: Change in pH by IC Bioreactor

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Fig 3.2: pH Change in Mixed Culture Plants

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Fig 3.3: Change in pH by Mixed Culture Algae

3.2 Electrical conductivity trend in IC bioreactor and CWs

Initially the concentration of EC in wastewater was 1547 µS/cm. shown in (Fig 3.4). Average EC reduced to 921 µS/cm with the removal efficiency of 40%. Maximum removal efficiency was found on 20th day 47 % shown in (Fig 3.4). EC trend was changed in mixed culture of plants, it increases by increasing operational days. Average increase of EC in mixed culture of plants and algae was 1320 µS/cm and 1350 µS/cm shown in (Fig 3.5 and Fig 3.6).

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Fig 3.4: Electrical Conductivity Reduction by IC Bioreactor

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Fig 3.5: EC Change by Mixed Culture Plants

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Fig 3.6: Change in EC by Mixed Culture Algae

3.3 Reduction in Turbidity

Turbidity of “Jaricus” wastewater was reduced throughout operational days by IC bioreactor treatment as shown in (Fig 3.7). Initially NTU of wastewater was 392 NTU, and after treatment it was reduced 44.7 NTU with the removal efficiency of 89%. From first day onward turbidity of influent fluctuates, but turbidity of effluent decreases and its removal efficiency increases up to 99%. maximum removal efficiency was observed 99% on day 10th, and 17th. Overall significant turbidity removal efficiency trend was ranges between 85% to 99% (Fig 3.7).

(Fig 3.8) shows turbidity reduction by mixed culture of plants and Algae had initial concentration 12.0 NTU which reduced up to 1.5 NTU with average removal efficiency of 87.5%. (Fig 3.9) shows turbidity NTU increasing trend in mixed culture of Algae due many factors, its average concentration increases from 12.0 to 123 NTU shown in (Fig 3.9).

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Fig 3.7: Reduction in Turbidity by IC Bioreactor

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Fig 3.8: Turbidity Reduction by Mixed Culture Plants

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Fig 3.9: Change in Turbidity by Mixed Culture Algae

3.4 Reduction of COD

On startup of IC bioreactor, it shows less COD removal efficiency from day 1st to 4th. The removal efficiency increased from the day 4th onward as shown in (Fig 3.10). Maximum COD removal efficiency was depicted as 97% and 95% on day 13th and 18th with the COD concentration of 433 mg/L and 960 mg/L. Minimum COD removal efficiency was found 42% on day 2nd had the COD concentration of 371 mg/L. Overall COD removal efficiency trend increased by increasing operational days (Fig 3.10). Average COD reduction of IC bioreactor was 355 mg/L. COD of Mixed culture of plants is depicted in (Fig 3.11). It significantly reduced average COD concentration of effluent was 38.2 mg/L with the removal efficiency of 89%. The COD concentration of mixed culture algae was reduced COD in small amount, average COD concentration in effluent was 267 mg/L with average removal efficiency of 25% shown in (Fig 3.12).

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Fig 3.10: Reduction in COD by IC Bioreactor

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Fig 3.11: COD Reduction by Mixed Culture Plants

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Fig 3.12: COD Reduction by Mixed Culture Algae

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3.5 Nickel reduction

Initial concentration of nickel (Ni) in wastewater was 3.5 mg/L (Fig 3.13), which was brought from “Jarikus”, which was fed into Internal Circulation (IC) Bioreactor. With the passage of time its concentration reduces in the effluent of bioreactor. After three weeks of treatment concentration reduced to 0.55 mg/L (Fig 3.13) with the removal efficiency of 77%. Initial concentration of Ni in influent 1.8 was mg/L, which fed into CWs with mixed culture of plants species, and mixed culture of algal species. Results of CWs planted with mixed culture of plants found high removal efficiency. After 2nd week of treatment mixed culture of plants obtained 80% of removal efficiency. At the end its concentration reduced to below detection limits (BDL) with the removal efficiency of 100% (Fig 3.14). Results of mixed culture of Algae found less removal efficiency 57% (Fig 3.15). Mixed culture of algae shown less removal efficiency as compared to mixed culture of plants.

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Fig 3.13: Nickel Reduction by IC Bioreactor

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Fig 3.14: Nickel Reduction by Mixed Culture Plants

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Fig 3.15: Nickel Reduction by Mixed Culture Algae

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Fig 3.16: Comparison of Nickel Concentration Reduction

3.6 Cadmium Reduction

Initial concentration of cadmium (Cd) in wastewater was 3.5 mg/L (Fig 3.17), which was fed into Internal Circulation (IC) Bioreactor. By increasing working days of IC bioreactor its concentration reduced in the effluent which was 1.15 mg/L had removal efficiency of 36% (Fig 3.17) Average initial concentration of Cd in influent was 1.7 mg/L, which fed into CWs with mixed culture of plants species, and mixed culture algal species. Mixed culture plants obtained high removal efficiency at 2nd and 3rd week had removal efficiency of 98% and 100% (Fig 3.18) while mixed culture algae reduced Cd concentration 0.155 had removal efficiency of 72% at 3rd week of treatment (Fig 3.19). In comparison, mixed culture plants shows high reduction in Cd concentration below from NEQs which was 0.1 mg/L, while mixed culture algae reduced less reduction which does not meet NEQs (Fig 3.20).

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Fig 3.17: Cadmium Reduction by IC Bioreactor

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Fig 3.18: Cadmium Reduction by Mixed Culture Plants

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Fig 3.19: Cadmium Reduction by Mixed Culture Algae

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Fig 3.20: Comparison of Cadmium Concentration Reduction

3.7 Copper Reduction

Initial concentration of copper (Cu) in wastewater was 5.1 mg/L (Fig 3.21), its concentration reduced in IC bioreactor effluent. After three weeks of treatment average concentration reduced to 2.0 mg/L (Fig 3.21) had the removal efficiency of 61%. Initial concentration of Cu in influent was 2.0 mg/L, which fed into CWs for post treatment, CWs planted with mixed culture of plants species, and mixed culture of algal species. Results of CWs planted with mixed culture of plants found high reduction in 1st week of treatment which was 96% (0.0165 mg/L) shown in (Fig 3.22). In 3rd week of treatment mixed culture of Algae also removed Cu concentration up to BDL had removal efficiency of 100% (Fig 3.23). In comparison mixed culture plants shows high removal efficiency at 1st week but mixed culture algae found high removal in 3rd week of treatment shown in (Fig 3.24).

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Fig 3.21: Copper Reduction by IC Bioreactor

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Fig 3.22: Copper Reduction by Mixed Culture Plants

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Fig 3.23: Copper Reduction by Mixed Culture Algae

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Fig 3.24: Comparison of Copper Reduction

3.8 Zinc Reduction

Initially concentration of Zn was 16.5 mg/L, which was fed in IC bioreactor for treatment after 3 weeks of operational days its average concentration reduced up to 9.5 mg/L had removal efficiency of 42% (Fig 3.25). This effluent was post treated by Mixed culture of plants and algae. Results of CWs planted with mixed culture of plants found high reduction in 2nd and 3rd week of treatment which was 95% (0.0895 mg/L) and 100% (BDL) shown in (Fig 3.26). In 3rd week of treatment mixed culture of Algae also removed Zn concentration up to 2.6 mg/L had removal efficiency of 40% (Fig 3.27). In comparison mixed culture plants shows high removal efficiency but mixed culture algae found less removal throughout treatment period shown in (Fig 3.28).

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Fig 3.25: Zinc Reduction by IC Bioreactor

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Fig 3.26: Zinc Reduction by Mixed Culture Plants

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Fig 3.27: Zinc Reduction by Mixed Culture Algae

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Fig 3.28: Comparison of Zinc Concentration Reduction

3.9 Lead Reduction

Initially concentration of Pb in wastewater was 6.5 mg/L, which was treated by IC bioreactor for biological treatment after 3 weeks of operational days its average concentration reduced to 3.08 mg/L had removal efficiency of 53% (Fig 3.29). This effluent was post treated by mixed culture plants and algae. Results of CWs planted with mixed culture of plants shows high reduction in 2nd and 3rd week of treatment which was 81% (0.025 mg/L) and 100% (BDL) shown in (Fig 3.30). In 3rd week of experiment mixed culture of Algae also removed Pb concentration up to 0.15 mg/L had removal efficiency of 40% (Fig 3.31). In comparison mixed culture plants shows high removal efficiency but mixed culture algae found less removal throughout treatment period shown in (Fig 3.32).

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Fig 3.29: Lead Reduction by IC Bioreactor

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Fig 3.30: Lead Reduction by Mixed Culture Plants

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Fig 3.31: Lead Reduction by Mixed Culture Algae

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Fig 3.32: Comparison of Lead concentration Reduction

3.10 Phosphate reduction

Initial concentration of phosphate in wastewater was 56 mg/L, which was brought from “Jarikus”, which was fed into Internal Circulation (IC) Bioreactor. With the passage of time its concentration reduces in the effluent of bioreactor. After three weeks of treatment concentration reduced to 11.6 mg/L (Fig 3.33) with the removal efficiency of 55%. Initial average concentration of influent was 19.6 mg/L, which fed into CWs with mixed culture of plants species, and mixed culture of algal species. Concentration reduced with the passage of time, after three weeks of treatment its concentration was 0.35 mg/L and 1.9 mg/L, with the removal efficiency of 83% and 70% shown in (Fig 3.34 and Fig 3.35). In comparison high phosphate concentration reduced in mixed culture plants compared to mixed culture algae shown in (Fig 3.36).

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Fig 3.33: Phosphate Reduction in IC Bioreactor

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Fig 3.34: Phosphate reduction by Mixed Culture Plants

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Fig 3.35: Phosphate Reduction by Mixed Culture Algae

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Fig 3.36: Comparison of Phosphate Reduction

3.11 Nitrate Reduction

Initial concentration of Nitrate in wastewater was 131 mg/L, which was brought from “Jarikus”. After treatment from IC bioreactor reduced to average concentration of 47 mg/L had removal efficiency of 64% shown in (Fig 3.37). Further treated by CWs planted with mixed cult

ure of plants and Algae. Mixed culture plants shows high removal efficiency 65% (3.5 mg/L) in 3rd week of treatment (Fig 3.38). In mixed culture algae setup shows removal efficiency of 60% (14 mg/L) in 2nd week of treatment, but its removal efficiency reduced from 60% to 51% (Fig 3.39). In comparison high nitrate concentration removal was noticed in mixed culture plants compared to mixed culture algae shown in (Fig 3.40).

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Fig 3.37: Nitrates Reduction by IC Bioreactor

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Fig 3.38: Nitrate Reduction by Mixed Culture Plants

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Fig 3.39: Nitrates Reduction by Mixed Culture Algae

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Fig 3.40: Comparison of Nitrates Reduction

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3.12 Sulphates Reduction

Initial concentration of sulphates in wastewater was 51 mg/L, after treatment from IC bioreactor its concentration reduced to average concentration of 22 mg/L had removal efficiency of 57% shown in (Fig 3.41). Further treated by mixed culture of plants and Algae. Mixed culture plants shows high removal efficiency 76% (0.95 mg/L) in 3rd week of treatment (Fig 3.42). In mixed culture algae setup shows removal efficiency of 66% (4.5 mg/L) in 2nd week of treatment (Fig 3.43). In comparison high sulphates concentration removal was observed in mixed culture plants compared to mixed culture algae shown in (Fig 3.44).

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Fig 3.41: Sulphate Reduction by IC Bioreactor

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Fig 3.42: Sulphates Reduction by Mixed Culture Plants

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Fig 3.43: Sulphates Reduction by Mixed Culture Algae

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Fig 3.44: Comparison of Sulphate Reduction

Table 3.1: Metals removal concentration by IC bioreactor and Post treatment

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Chapter 4 Discussion

4.1 Discussion

In recent years, wastewater treatment approaches have been transferred to one of the most promising procedures, i.e. biological anaerobic process with the start of high rate organic system, like anaerobic digester (AD). Beneficial characteristics of high rate AD includes, microbial consortia can aggregate and form granules, low operational and maintenance costs, energy recovery in terms of biofuel production, simple to operate, consume low energy and produces less biomass (digested sludge) (Ji et al., 2013; Khan et al., 2011; Gomec, 2010; Van Handeel and Lettinga, 1194). Developing nations suffered due to lack of financial recourses, energy crises, and above mentioned advantages. So, this approach is most feasible for wastewater treatment. In spite of various modification, AD effluent hardly meets the discharge standards. (Lew et al 2003; Khan at al 2011).

Presently 200 Anaerobic Digesters can be used for Muncipal, and Industrial applications (Khan et al., 2012; Khan et al., 2011). Treated effluent from AD can be used in agriculture sector for farming, but such type of AD effluents contains high concentration of COD, BOD and coliform bacteria. So, this approach is unable to meet international discharge standards of effluent into the open environment and reuse for agriculture irrigation, that causes serious damage aquatic organisms. However, the effluent discharged from AD into water bodies like rivers, lakes, post treatment is an essential approach (Sato et al., 2006; Verstraete and Vandevibere 1999).

The treatment efficiencies of IC bioreactor were depicted in Table3.1. Before treatment COD of wastewater ranges 285-1192 mg/L, after treatment by IC bioreactor its average concentration reduces to 355 mg/L with the removal efficiency of 51%.This concentration is not reached to NEQs value (150 mg/L). Then after post treatment by mixed culture plants its concentration further reduced to average concentration of 38 mg/L with removal effeciency of 89% which is below NEQs. But post treatment through mixed culture shows 267 mg/L (25%). The selected metals (Pb, Ni, Cu, Cd, Zn) treatment was shown in Table 3. It was noticed that IC bioreactor remained unsuccessful in meeting the NEQs for heavy metals removal like Pb, Ni, Cu, Cd, Zn. IC bioreactor shows removal efficiency regarding metal removal was 53% (3.08 mg/L), 49% (1.8 mg/L), 60% (2 mg/L), 52% (1.7 mg/L) and 42% (9.5 mg/L) respectively. After post treatment of 3 weeks by mixed culture plants its concentration further reduced to; 87% (0.4 mg/L),88% (0.22 mg/L), 99% (0.0235 mg/L), 98% (0.037 mg/L), 92 % (0.8 mg/L) respectively. Mixed culture of Algae shows less removal efficiency for metals 55% (1.4 mg/L), 44% (1.0 mg/L), 83 %(0.35 mg/L), 96% (0.623 mg/L), 53% (5 mg/L) respectively which was shown in Table 3.1. Turbidity of wastewater was 392 NTU , and after treated through IC bioreactor ,its Concentration reduced 44.7 NTU with the removal efficiency of 89% , while turbidity further reduced by mixed culture plants was 1.5 NTU with the removal efficiency of (99%) but Algae increases turbidity due to organic content and heavy metals in wastewater. Electrical conductivity ranges from 785-1647 through out the process. Which was reduced 921 µs/cm in IC bioreactor , and increased in mixed culture plants and algae CWs. Initial concentration of phosphate was 56 mg/L , which reduced to 11.6 mg/L (55%) , futher reduced to 0.35 mg/L (85%) in mixed culture plants, and Algae had 1.9 mg/L (70%). NEQs value for phosphates (2 mg/L). Initial concentration of sulphates was 51 mg/L , which reduced to 22 mg/L (57%) , futher reduced to 0.95 mg/L (96%) in mixed culture plants, and Algae had 4.5 mg/L (80%). NEQs value for sulphates (250 mg/L). Initial concentration of nitrates was 131 mg/L , which reduced to 47mg/L (64%) , futher reduced to 3.5 mg/L (65%) in mixed culture plants, and Algae had 14 mg/L (60%). NEQs value for nitrates (0.15 mg/L). Algae and bioreactor was not meeting the NEQs standards for wastewater treatment.

It was reported that due to complex nature of industrial wastewater, AD was unsuccessful to meet the NEQs. During the process of AD for organic matter, many biochemical reactions take place which are effected by heavy metals concentration (Mudhoo et al., 2012). The major cause of these fluctuations is the complexity of Anaerobic digestion process where various mechanisms significantly affect inhibition process. These mechanisms are; (antagonism, synergism, acclimation, and complexing). The major reasons are found for the anaerobic digester upset and failure are inhibitory substances, which effects microbial population and bacterial growth is present in bioreactor (Chen, 2008). The most common and important form of HMs are precipitation as sulfides carbonates, and hydrocarbons, sorption on to solid phase (Inhibitory effects of heavy metals on biomass (Anaerobic sludge) (Sarioglu et al., 2010). In Anaerobic digestion process methanogens in wastewater treatment systems are working more effectively in the neutral pH range (7.0) (Florencio et al., 1993). The appropriate pH range for microbial consortia is 6.0– 9.0. The living organisms present in anaerobic digester inhibited at pH 9 was able to regain performance after regulating the pH to neutrality, but that inhibited at pH 5 was not regain its activities (Fang and Jia, 1998). When the biogas generation stabilizes, the pH range is remaining between 7.2 and 8.2.

However, the residual amount of organic pollutants such as, (COD and BOD), In effluent of anaerobic digester exceeds the maximum permissible level suggested through effluent discharge standards for developing nations (Kumar et al.,2009; Prakash et al., 2007; Sato et al., 2006; Machdar et al., 2000). Due to these view point, post treatment of anaerobic treatment effluent was deemed mandatory to reduce these parameters up to permissible limit.

4.2 Post treatment of IC bioreactor effluent by mixed culture Plants and Algae

Phytoremediation, which encompasses green and environment friendly approaches that employ plants to remove contaminants from the neighboring habitat, has attracted increasing attention in ecological studies because of its safety, high efficiency, low cost, and recyclability of plant harvests. However, the technology is often limited by its time-consuming feature because the life cycle of most plants used for phytoremediation is excessively long (Agunbiade et al., 2009). However, this disadvantage may not be apparent in the alien plants water hyacinth and water lettuce because of their enormous biomass production. Aquatic plants are highly sensitive to the temperature and pH of the growing media.

The summary of the treatment of IC bioreactor effluent by mixed culture of plants species (E.crassipes , and Giant reed ) planted in CWs was found successful in treating the IC bioreactor effluent. Treatment through plants were able to significantly reduce the pollutant concentration, Such as turbidity, phosphate, nitrates, sulphates, COD, and Heavy metals (Cu, Zn, Pb, Cd, Ni). All results that was observed from mixed culture plants and mixed culture algae was shown in Table 3 these treatment was able to remove pollutants up to permissible level set by EPA Pakistan. Mixed culture plants shows removal efficiency of 80 to 95%.

The pH of the water is the measure of Hydrogen ion activity of the water system. It directs whether the water is neutral, acidic, or alkaline in nature. In the process of biosorption, pH looks to be the most important parameter, because it effects chemistry of metals with solvent, the activity of functional groups in biomass and competition of metallic ions. The change in pH may be due to release of root exudates in response to the stress to acclimatize itself with the present habitat (Borker et al., 2013). This slight increase in pH mainly due to photosynthetic activities of emergent plants which depleted dissolved CO2 from the water and raised the water Ph. The maximum increase in biomass production occurred at neutral and slightly alkaline pH (pH 7 and 8), which may be due to the increase in nutrient uptake and immobilization capacity of the water hyacinth samples (Ayaz et al., 2012).

Turbidity is delirious to aquatic fauna and cause anaerobic conditions. It can cause respiratory problems in aquatic organisms, also stop entrance of sunlight in aquatic system that hindering in process of photosynthesis and natural aquatic life. Turbidity removal efficiency in constructed wetland depends on the sand granules, sizes of soil particle and depth of the bed (Malec et al., 2009). The turbidity reduction after post treatment` in constructed wetland with mixed culture plants (Water hyacinth and A.donax), algae and control might be due to settling down of sediments. The highest turbidity reduction achieved by constructed wetland with mixed culture plants as compared to algae control might be due to adsorption of particles on extensive roots of water hyacinth and A. donax.

The decrease in COD values in CW with E.crassipes and A.donax might be due to high biodegradation of organic pollutants of wastewater during constant biological activities in the plants, because of dense root hair structure. The removal of organic matter might be due to settling and entrapment of particulate in the void spaces of the substrate. The substrate is substantial for plants and microbial growth. The microorganisms attached to the root zone of the plants play a very important role in the degradation of organic matter. They use organic compounds as their food source and convert them into carbon dioxide. In this process, the oxygen is supplied by the roots of the plants. Soluble organic matter may also be removed by number of separation processes including absorption and adsorption (Faulwetter et al., 2009). High COD and BOD reduction can be imputed due too many reasons, hydrophytes have the unique characteristics of transporting oxygen from ariel parts to its submerged portion of plants, that helps to increase the oxygen content of water in the sub canopy of macrophytes (Hartman and Eldowney, 1993). Low availability of oxygen results poor removal of organic matters. Although, sedimentation and adsorption are known to be possible mechanisms for COD and BOD removal. (Priya and Selvan, 2014) tells emergent plant species have greater potential to accumulate heavy metals present inside their plant bodies. Heavy metals are accumulated by the plant roots, translocated to the shoots and other plant tissues, where they are concentrated and harvesting the plant can permanently eliminate these pollutants. In CWs majority of metals are removed by these mechanisms: metal binding to sediments, particulates, through cation exchange, chelation, precipitation, adsorption and accumulation through plants. Removal of heavy metals from the contaminated environment by the process of adsorption and precipitation, and plant uptake. Metals are retained in substrate, sediments and soil profile, precipitate out as sulphides and carbonates, or accumulate through plants roots (Kamarudzaman et al., 2011; Renee, 2001; Kadlec 1999).

Nitrogen and phosphorous are two main nutrients found in wastewater in high quantities. High levels of phosphorus in effluent can also cause eutrophication in water bodies. Phosphorus is present in the wastewater in the form of orthophosphate and organic phosphorous, which is found in the wetlands as part of sediments. Adsorption is the most important phosphorus removal process in the wetlands. Adsorption of phosphorus occurs due to reactions with calcium present in sediments. Constructed wetlands are capable of removing N and P by treating wastewater. Growing plants take up nutrients like phosphorus, thereby reducing levels in the wetland (Bama et al., 2013). Total phosphate removal mechanism in the constructed wetland includes filtration, sedimentation, chemical reactions in the substrate, uptake by plants, and assimilation by microorganisms. Phosphorus removal in wetlands could be through the accretion of wetland soils, plant uptake, retention by root bed media, microbial immobilization, and precipitation in the water column (Vohla et al., 2005).

Removal process of nitrogen are: Volatilization, diffusion, filtration, Nitrification and Denitrification through microbes (Brix,1987; Vymazal et al., 1998). Of these, bacterial process has the most effect on the overall nitrogen removal. Nitrosomonas and nitrobacter nitrify ammonia into nitrates which is available for plant and microbial uptake. Denitrifying bacteria convert nitrate into gaseous nitrogen, which gets volatilized (Arivoli and Mohanraj, 2013). Suspended solids are removed through these mechanisms; Sedimentation, filtration, aggregation and surface adhesion (Kadlec and Knight, 1996; Peng et al., 2014). In CW total solids and total dissolved solids are removed by the roots of macrophytes through the process of filtration (Hartman and Eldowney, 1993).

4.3 Algae

Microalgae integrate a substantial amount of nutrients because they require high amounts of nitrogen and phosphorus for the synthesis of proteins, nucleic acids, ATP, and phospholipids (Oswald, 2003). The oxygen and pH variation tempted through photosynthetic process in microalgae helps to reduce coliform and other pathogenic bacteria in the effluent of wastewater (Metcalf and Eddy, 2003; Kiso et al., 2005).

Most heavy metals shown high toxicity and carcinogenic mediators and when releases into the wastewater epitomize a serious threat to the human life, fauna and flora the receiving water bodies (Monika et al., 2014).

The algae have various characteristics which make them suitable for the selective removal of pollutants like heavy metals. Algal species have high biosorption capacity, high ability to tolerate many heavy metals, capability to grow both autotrophically and heterotrophically, large surface area/volume ratios, phototaxy, phytochelatin generation and its potential for genetic manipulation (Chekroun and Baghour, 2013; Kumar et al., 2015). It is well recognized that numerous marine and fresh water algal species are able to accumulate heavy metals within their cells from aquaeous medium (Afkar et al., 2010; Kumar and Gaur, 2011; Chen et al., 2012). Several researches observed that different species of varous fresh water microalgae like Chlorella sp., Anabaena sp., Westiellopsis sp., Stigeoclonium sp., Synecococcus sp. etc. have high tolerance capacity for many heavy metals (Dwivedi, 2012). Microalgae are photosynthetic microorganisms that uses energy from the sun to grow, consuming inorganic nutrients and CO2, they accumulate organic matter in the form of proteins, lipids, carbohydrates, hydrocarbons and other small molecules and pigments (Ruiz-Martinez et al., 2012). They are primary producers for organic compounds; and play a important role as the base of the food chain in aquatic systems (Abdel Raouf et al., 2012).

Conclusions

- Combined wastewater from various industrial sources in HIE was collected and characterized. Characterization showed that the wastewater from HIE was of medium strength in nature, based on its characteristics analyzed by standard method.
- While treating HIE wastewater by IC bioreactor it was found that considerable reductions in COD, turbidity, sulphates, nitrates, phosphate.But still reactor was not successful in meeting NEQs of the country. Post treatment in natural treatment system was thought as suitable option for post treatment.
- The post treatment consisting of mixed culture of plants like water hyacinth, Aroudo donax and another containing mix micro algae used as post treatment of IC bioreactor. It was found that the plant culture was better choice to reduce COD, turbidity, sulphates, phosphates nitrates and heavy metals with in permissible limits. Being indeginous plants the combination of Aroudo donax and water hyacinth are recommended for better environmental protection.
- Algal post treatment resulted in severe inhibition of biomass growth as it resulted in increasing EC, turbidity, which were indicative of cellular damage as a result of wastewater treatment.

Recommendations

- The most suitable treatment methods for industrial wastewater are biological treatment approaches, especially anaerobic wastewater treatment along with post treatment wetland processes.
- The effective management of any wastewater flow requires a reasonably accurate knowledge of its characteristics. Futher studies and their awairness needed for wastewater treatment and discharge.

Chapter 5 References

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• Curso: Envirmantal Science
• Autor: Usman Khan Khan (Autor)
• Año de publicación: 2015
• Páginas: 82
• No. de catálogo: V378734
• ISBN (Ebook): 9783668589537
• ISBN (Libro): 9783668589544
• Idioma: Inglés
• Etiqueta: COMBINED INDUSTRIAL WASTEWATER TREATMENT IN CONSTRUCTED WETLAND SYSTEMS CONTAINING EMERGENT PLANTS AND ALGAE