Integrated Approach for Wastewater Treatment - A ...

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Aerated lagoons (ponds) evolved from facultative stabilization ponds when surface aerators were installed to overcome the odors from organically overloaded ...
ETWMT-09: Indo-Italian Conference on Emerging Trends in Waste Management Technologies, Dec. 3-4, 09, MAEER’s MIT College of Engineering, Pune & Maharashtra Institute of Technology, Pune

Integrated Approach for Wastewater Treatment A Focus On Energy Generation G B Shinde1, R S Vaidya2, L. Govindarajan3, N B Raut4 Department of Chemical Engg, SVMEC, Nasik. 2Department of Applied Science, Bramhavalley College of Engineering, Nasik 3 Dept. of Mechanical & Industrial Engg. Caledonian College of Engineering, Sultanate of Oman 4 Department of Chemical Engineering, Sohar University, Sultanate of Oman 1

ABSTRACT Treatment of industrial and domestic wastewater pose many problems in terms of treatment, cost, legislation and adherence to pollution control norms set by various agencies. Wastes contain many compounds that can be potential use for the generation of energy especially bioenergy by the use of suitable and appropriate biochemical treatment methods. This paper aims to address an integrated approach for the treatment of industrial and domestic wastewater with aim of generating bioenergy fr om the waste.

KEY WORDS: UASB, ISP, CWL, PVAB, microalgae, Waste Water Treatment (WWT) 1. INTRODUCTION The usage pattern of water by human beings is untenable as the water resources are getting depleted at a faster rate. This is due to the increase in sophistication and modern life style. Water from the soil, rain or irrigation, through the evapotranspiration of plants, creates food, and the water involved is “lost” to the water cycle. Foods differ in their water impact . For example to process a kilo of wheat uses about 1 ton of water; rice uses about twice that amount and five times is required for chicken. The increase in energy use that comes with prosperity also results in additional water demand. Producing a liter of oil uses three liters of water. From an energy point of view, water provision in wealthy societies can be very energy intensive. For example, the oil used in the production, transportation and disposal of a bottle of water is, on average, equal to filling that bottle one-fourth of the way with oil, and about 3.24 watt-hours of power is used to produce a liter of desalinated water. Pollution makes water unusable and increases the pressure on the water resource. Water cannot be created and has no substitute (unlike energy forms), but it can be managed better. In particular, we need to be able to grow more food with less water. The science is available, but too often the incentives for water use run backwards – to increase the demand for water and not to foster change. Our trade policies do not encourage optimal water use. We need as vibrant a market for used water as there is for used cars – extracting the nutrients for crops (in a world of skyrocketing fertilizer prices), using lightly treated water for appropriate industrial and agricultural purposes and even contributing to energy via anaerobic methane production from wastewater. Water can and should be discussed globally, but can be truly understood and acted upon only locally. Water is intensely political who gets it, who can use it, whether they pay or not and whether polluters are regulated and apprehended. All of this is the stuff and substance of local politics. Good industrial and agricultural use patterns depend on stable policy climates water improvement does not come about unless public policies change. So perhaps the most important task for the business community is to help create the climate in which governments can make better decisions about protecting water and making water use and reuse more productive. 1.1 Potential of Wastewater as a Water Resource Treated wastewater is the only source of additional water for agriculture, industry and urban non-potable reuse that actually increases in quantity as the population grows, while more water is demanded by urban and industrial sectors. If it is assumed that the total domestic/urban/industrial water supply eventually reaches 125 cubic meters/year, and then it is not unreasonable to estimate, based on experience in various countries, that anywhere between 65-80% of the incoming water supply can be treated and reused. Thus for example, a city with a population of one million would require a water supply of 125 million cubic meters/year and under optimal conditions, eventually some eighty percentage of that amount could be collected in the central sewerage network, treated and reused in adjacent agricultural areas. In this case, some 100 million cubic meters/year of treated wastewater might be made available to agricultural areas adjacent to the city. The amount of water would be sufficient to irrigate between 10 to 20 thousand hectares depending on the irrigation technology used, the type of crops and other local conditions. If achieved, such treatment and reuse of properly treated and purified wastewater can without risk to the health of the public add significant amounts of water to the agricultural sector. Based on water demand for various crops this treated water can result in a substantial decrease in the demand to grow all of the fresh food crops required by the urban population. Alternatively, it could be used for higher valued industrial purposes and even for still higher value, urban, non-potable purposes such as the irrigation of greenbelts, parks gardens and recreation areas. 676

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2. WASTEWATER TREATMENT TECHNOLOGIES In wastewater treatment, contaminants are removed by physical, chemical, and biological means and the treatment methods are usually classified as physical, chemical, and biological processes (Metcalf and Eddy, Inc. 1979, and Steel and McGhee 1979). The physical wastewater treatment process applies physical forces. Typical physical processes are screening, mixing, flocculation, sedimentation, flotation, and filtration. Chemical treatment processes remove or convert the contaminants by adding chemicals or through chemical reactions. The most common examples used in chemical wastewater treatment are precipitation, gas transfer, adsorption, and disinfection. Chemical precipitation, for example, is accomplished by producing a chemical precipitate, which will settle at the end. A biological treatment is used primarily to remove the biodegradable organic substances (colloidal or dissolved) in wastewater. Basically, these substances are converted into gases that can escape to the atmosphere or into biological cell ti ssues that can be removed by settling. Biological treatment is also used to remove pathogens and nitrogen from wastewater. In most cases, wastewater can be treated biologically. The four major groups of biological treatment processes are aerobic, anaerobic, anoxic (the process by which nitrate is converted biologically into nitrogen gas in the absence of oxygen), or a combination of the three. The principal applications for these processes are removing carbonaceous organic matter (measured in BOD, COD, or in TOC), nitrification, denitrification, or stabilization. The most common wastewater treatment method used in many regions with hot to moderate climate regions is a stabilization pond. 2.1 Stabilization Ponds Stabilization ponds are a suitable treatment technology because they are also very effective at removing pathogens (WHO 1987). Stabilization ponds consist of a series of ponds into which the sewage flows. Treatment occurs through natural physical, chemical, or biological processes and no extra energy is required except the sun. Such treatment methods are the cheapest and simplest of all the treatment technologies and are capable of providing a very high-quality effluent. Ponds are very easy to maintain and require no routine operation. They can absorb both hydraulic and organic disturbances and can treat a wide variety of domestic and industrial wastes. The system can be flexible and can be expanded with little investment. Stabilization ponds can also be used to convert the emitted gases into useful energy. The biogas produced from the biological processes can be collected and used to produce energy (either electricity or heat or both). The biggest disadvantage of stabilization ponds is that they take up a lot of space. 2.2 Anaerobic Ponds Anaerobic ponds are basically open septic tanks used for pre-treating large volumes of strong wastes. Anaerobic digestion involves the decomposition of organic and inorganic matter in the absence of molecular oxygen. In anaerobic ponds, anaerobic digestion and settling will take place, and a thick scum usually develops on the surface. Retention times typically vary from 1–4 days, and the preferred pond depth is 2–4 m. Odor can be avoided by controlling the volumetric load of the BOD (not more than 400 g/m3/day) and the concentration of sulfate ion in the raw waste (not higher than 100 mg/l). 2.3 Facultative Ponds Facultative ponds are a combination of aerobic, anaerobic, and facultative bacteria. Facultative processes are biological treatment processes in which the organisms are indifferent to the presence of dissolved oxygen (these organisms are known as facultative microorganisms). There are three zones in facultative ponds: (1) a surface zone where aerobic bacteria and algae exist; (2) an anaerobic bottom zone in which accumulated solids are actively decomposed by anaerobic bacteria; and (3) an intermediate zone, which is partly aerobic and partly anaerobic, in which the decomposition of organic wastes is carried out by facultative bacteria. 2.4 Maturation Ponds Maturation ponds are wholly aerobic and are responsible for the final stage of the BOD removal, reducing the fecal bacteria and viruses. Generally, two or more maturation ponds must follow a facultative pond. As a rule of thumb, three maturation ponds are used with a retention time of five days and depths of 1–1.5 m. The retention time decreases as the number of maturation ponds increases, and increasing the retention time will also provide a greater chance of microbiological purification. In a warm climate, maturation ponds can remove 95% of fecal coli forms with a retention time of five days. Maturation ponds can also provide the best environment for fish farming. 2.5 Aerobic Stabilization Ponds Aerobic stabilization ponds are large, shallow earthen basins that are used to treat wastewater by natural processes involving algae and bacteria. In aerobic ponds, the oxygen is supplied by natural surface aeration and by algae photosynthesis. The bacteria in the aerobic degradation of organic matter use the oxygen released by the algae through photosynthesis. The al gae in turn, use the nutrients and CO2 released in this degradation. The main function of aerobic stabilization ponds is to further purify the effluent. 677

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2.6 Aerated Lagoons/Oxidation Ditches These kinds of ponds are also called “high-rate” stabilization ponds because the treatment approach is to speed up the conversion of organic wastes into algae by using a motorized aeration system. Aerated lagoons (ponds) evolved from facultative stabilization ponds when surface aerators were installed to overcome the odors from organically overloaded ponds. If a facultative pond is too small, or if toxic substances or lack of sunlight prevent the algae from adequately photosynthesizing, the BOD will exceed the oxygen supply and the pond will turn anaerobic. In that case, it may require extra oxygen to be supplied by mechanical means. Such a method is called mechanical aeration or an aerated lagoon. 2.7 Other Emerging Technologies in WWT Renewable energy technologies, such as wind, solar, biogas, and their hybrids, with or without backup diesel generators, (Meliβ et al 1998) are very attractive methods for fulfilling the energy needs of wastewater treatment systems. Using biogas produced from the wastewater for gas generation or cogeneration is also possible and desirable. 2.7.1 Solar Detoxification Solar radiation energy (direct sunlight) has been used for the biological processes in stabilization ponds. Now there are new emerging technologies for treating wastewater that use the UV portion of the solar spectrum to activate the semiconductor catalyst that produces hydroxyl radicals. Solar energy has long been used for water purification and disinfection. The same principle is used to treat hazardous wastes in water, air, and soil. 3.THE INTEGRATED APPROACH In this paper integrated wastewater treatment approach is defined as per the technical, economic, social and environmental requirements when planning the water treatment and implementing the complex series of interrelated activities i n an efficient and comprehensive manner. The proposed integrated approach is based on the following principle objectives:  To promote a dynamic, iterative, interactive and multispectral approach to water resources management, including the identification and protection of potential sources of freshwater supply that integrates technological, socio-economic, environmental and human health considerations.  To plan the sustainable and rational utilization, protection, conservation and management of water resources based on community needs and priorities.  To identify and strengthen or develop, an appropriate mechanism to ensure that treated waste water and its implementation is a catalyst for sustainable social progress and economic growth. Wastewater Preliminary Treatment HUASB

PVAB

ISP CWL

Gasification

Reservoir

Algal Biomass

Syn Gas

Combustion

Fermentation Methane/ Ethanol

Irrigation & Plantation

Electricity

Extraction H2

Bio-Oil

Fuel Cell Methanation/ Fermentation

Biophotolysis

Fig.1 Schematic for Integrated WWT

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ETWMT-09: Indo-Italian Conference on Emerging Trends in Waste Management Technologies, Dec. 3-4, 09, MAEER’s MIT College of Engineering, Pune & Maharashtra Institute of Technology, Pune

The proposed system will consists of hybrid up flow anaerobic sludge blanket (UASB) reactor, passively aerated vertical bed (PAVB), Intermittent Sand Filter (ISF), constructed wetland (CWL) and reservoir. The CWL will be used to cultivate suitable microalgae e.g. Chlorella, Spirulina, etc which will be harvested and dried. The design will have the maximum flexibility to facilitate the treatment of different wastewater.

4. LITERATURE REVIEW The number of summits related to the environment and development has resulted in international awareness and consciousness for protection of environment and water resources. This includes 1992 Rio Earth Summit, 2002 World Summit on Sustainable Development. There has been a rapid growth in multilateral environmental agreements like the Kyoto Protocol and the Stockholm Convention on Persistent Organic Pollutants. Sustainable development strategies have been implemented at local, national, regional and international levels. An increasing number of scientific assessments including the Intergovernmental Panel on Climate Change have contributed to a greater understanding of environmental challenges. In addition, proven and workable solutions have been identified for environmental problems that are limited in scale, highly visible and acute. (Global Environment Outlook, 2007).Sabbah et al had investigated the appropriate technologies for wastewater treatment and reuse. The results indicate that the combination of extensive and semi intensive treatment systems is an efficient way for treatment and reuse of wastewater in rural areas. Specifically, it was found that the up flow anaerobic sludge blanket (UASB) bioreactor system can be a good alternative for anaerobic ponds, significantly reducing the required area with better performance. The effluent of the UASB can be fed directly to either intermittent sand filter (ISF), or constructed vertical or horizontal wetlands. The importance and need of renewable and carbon neutral biofuels are necessary for environmental and economic sustainability is well explored by Patil et al 2008 in the research for sustainable production of biofuels from microalgae. Also, the viability of the first generation biofuels production is however questionable because of the conflict with food supply. Microalgae biofuels are a viable alternative. The oil productivity of many microalgae exceeds the best producing oil crops. Ron Putt in his studies for extraction of fuels from algal oil could either be biodiesel, which is a methyl ester produced via a straightforward reaction between most any vegetable oil and methanol, or straight (so called “green”) diesel, which is essentially the same as petro-diesel. Microalgae, as plants, store energy as carbohydrates and lipids, and these lipids are similar to those produced by crops. The meal remaining after extraction is rich (about 50%) in protein, and can therefore be used as a highvalue ingredient in animal feeds. The use of Hybrid Up flow Anaerobic Sludge Blanket (HUASB) reactor for treatment of domestic wastewater has been reported Banu et.al 2008. During the treatment, nutrient levels exhibited an increasing trend. HUASB system could be designed with very short HRT of 3.3 hours, which will reduce the treatment cost significantly. It appears to be a promising alternative for the treatment of domestic wastewater. A review by Torres et al present an account of the environmental pollution by organic compounds and metals due industrial activities and its intensification from environmental pollutants originating from diverse anthropogenic sources th ereby proving to be capable of degrading the ecological integrity of marine environment. The consequences of anthropogenic contamination of marine environments have been ignored or poorly characterized with the possible exception of coastal and estuarine waters close to sewage outlets. Monitoring the impact of pollutants on aquatic life forms is challenging due to the differential sensitivities of organisms to a given pollutant, and the inability to assess the long-term effects of persistent pollutants on the ecosystem as they are bio-accumulated at higher trophic levels. Marine microalgae are particularly promising indicator species for organic and inorganic pollutants since they are typically the most abundant life forms in aquatic environments and occupy the base of the food chain. Willie Driessen et al (2000) studied the use of a novel combination of tall and slender tanks and reactors for the treatment of industrial effluent at an urban place. This treatment requires Specific design to meet very strict constraints with respect to space, odors, view and biosolids production. The plant consisted of buffering, anaerobic and aerobic treatment, without sludge handling. Removal efficiencies are 80 % on total-COD and 94 % on soluble-COD were reported. R. Heidari et al reported that Evaporation basins can also provide a foundation for algae production. Yusuf Chisti (2008) et al summarized that microalgae appear to be the only source of biodiesel that has the potential to completely displace fossil diesel. Unlike other oil crops, microalgae grow extremely rapidly and many are exceedingly rich in oil. Microalgae commonly double their biomass within 24 hrs. Biomass doubling times during exponential growth are commonly as short as 3.5 h. Oil content in microalgae can exceed 80% by weight of dry biomass. Oil levels of 20–50% are quite common. Oil productivity, that is the mass of oil produced per unit volume of the micro algal broth per day, depends on the algal growth rate and the oil content of the biomass. Microalgae with high oil productivities are desired for producing biodiesel.

5. INTEGRATED WASTEWATER TREATMENT The schematic diagram of the integrated wastewater treatment is shown in Fig. 1.The waste water from industrial and domestic streams will be collected in a holding tank. This will undergo screening and preliminary treatment and flow to the stabilization tank through an intermittent sand filter. This waste water will be homogenized and dosed with HCl, NaOH, urea and phosphoric acid as per requirement. The feeder pump will feed this water at a particular flowrate to the hybrid up flow sludge 679

ETWMT-09: Indo-Italian Conference on Emerging Trends in Waste Management Technologies, Dec. 3-4, 09, MAEER’s MIT College of Engineering, Pune & Maharashtra Institute of Technology, Pune

blanket reactor provided with a water seal. The wet gases will be scrubbed off and gas will be stored in the gas holder with the scrubbed effluent flowing to the constructed wetland. Suitable algae viable for bioenergy generation will be cultivated on the constructed wet land from which the treated water will be stored in the reservoir. The treated water in the reservoir can be reused for short/long term plantation. The cultivated algae can be harvested to extract nutrients or cab be converted into useful forms of energy.

6. OUTPUTS When used in a fully engineered system, this approach will not only provides pollution prevention, but also allows for generation of energy, liquid fertilizer and nutrient recovery. Thus, it can convert a disposal problem into a profit center. As the technology continues to mature, the biogas technology is becoming a key method for both waste water reduction and recovery of a renewable fuel and other valuable co-products. Biogas projects have implications not only in the agro processing industrial sector, but in the agricultural and energy sectors as well, and among the environmental consequences, mitigation of pollution, greenhouse gas (GHG) emission reduction and reduced eutrophication of water etc. are important external effects. This integrated approach to waste water for energy conservation seems to be the most effective method to mitigate air pollution, greenhouse gases and water pollution. 6.1 Environmental and Social Consideration The comprehensive document of production results provided by the successive followup programs will prove that the concept offers integrated solutions to a range of environmental problems related to energy production and industry is comprehensive in both environmental and social consideration when compared to the conventional treatment. 6.2 Amount of Emissions Avoided The consideration of environment and social issues on amount of emissions avoided are listed as following: 6.3 Reduced load of BOD/COD discharge Anaerobic digestion of agro industrial wastewater results in reduction of organic carbon (BOD/COD) load to the environment. This biogas technology can convert organic carbon to methane and produce less microbial cell. The control of water pollution results in less impact on communities, agriculture, surface water, groundwater and ecology of aquatic life. 6.3 Reduced greenhouse gas emissions Biogas is a renewable energy source. Biogas plants contribute to reducing greenhouse gas emissions as the replacement of fossil fuels results in the reduction of CO2. In addition, CH4 emissions from open anaerobic lagoons of wastewater treatment can be reduced. CH4 are much stronger greenhouse gas than CO2. Further, methane is a potent greenhouse gas (GHG). The 100year Global Warming Potential (GWP) of methane is estimated to be 21. This means that a given mass of methane could increase the greenhouse effect by 21 times greater than the same mass of carbon dioxide. The generated biogas from wastewater is used to substitute fossil fuel for thermal heat from fuel oil and electricity from natural gas fired power plant including reduced water pollution. 6.5 Benefit to user There are a number of benefits resulting from the use of the proposed research approach 6.5.1 Energy Benefits 1. Net energy producing process 2. Generate high quality renewable fuel 3. Biogas proven in numerous end-use applications 6.5.2 Wastewater Treatment Benefits 1. Natural wastewater treatment process 2. requires less land than anaerobic lagoon 3. Reduces disposed sludge volume and weight to be disposed Environmental Benefits 4. significantly reduces carbon dioxide and methane emission 5. Eliminates odor 6. Produces a nutrient liquid for algal cultivation and plant irrigation & maximizes recycling benefits 6.5.3 Economic Benefits 1. Is more cost-effective than other treatment options from a life-cycle perspective. 6.5.4 Benefit to Community 680

ETWMT-09: Indo-Italian Conference on Emerging Trends in Waste Management Technologies, Dec. 3-4, 09, MAEER’s MIT College of Engineering, Pune & Maharashtra Institute of Technology, Pune

a. Increase manpower and income to the family especially in skilled labor b. The treated wastewater results in less odor nuisance than open impoundment lagoon to the adjacent community. Emissions of volatile solids and volatile fatty acids are directly related to odor strength released from organic fraction wastewater. The process can control odor and displaces fossil fuels. c. Reduced water pollution to surface water (canal and river) and groundwater that means to improve their healthy and aquatic life. Augmentation of water resource is the major benefit to the country. 6.5.5 Benefit to Region a. Reduced the amount of usage of fossil fuel and save the money for the country b. Reduced the GHG (CH4 and CO2) emission to the atmosphere that will effect to the country and world. c. Cheap and environmentally sound waste recycling. d. The environmental aspects include the sanitary effect of the digestion, as well as efficient fertilizer utilization of the effluent. Treating commodities to produce energy yield while recycling nutrients creates a virtuous cycle of sustainability. e. Promoting the technology transfer in country and region 6.5.6 Other Features Improved utilization of liquid fertilizer: The liquid fertilizer product is nutritionally defined. Consequently, treated agro industrial wastewater is more efficiently used as fertilizer, replacing chemical fertilizer production. The farmer can apply to their agricultural lands. More efficient fertilization at the same time results in less loss of nutrients and less water pollution from nutrients. The treated waste water can be used for irrigation and cultivation of microalgae using secondary treated wastewater

7. CONCLUSION This integrated approach will not only produce a more cost-effective biogas and algal product but will also reduce the environmental impact of the wastewater. Overall plants will compare favorably with its competitors as it provides recycling of a nutrients as well as generating renewable energy with minimum of air and water pollution emissions. This approach will generate biogas as renewable energy, reduce water pollution, utilize of treated wastewater for algal cultivation and plant irrigation, reduce in CH4 and CO2 emission, and decrease the odor nuisance problem to the adjacent community. This proposed approach provide lasting and relatively cheap and environment sound solution to wastewater problem. Economic benefit is more cost effective than other treatment options from a life-cycle perspective. It will create a virtuous cycle of sustainability.

REFERENCES [1.] Banu.J.R; S. Kaliappan; I. T. Yeom Treatment of domestic wastewater using up flow anaerobic sludge blanket reactor published in Int. J. Environ. Sci. Tech.,( 4 (3): 363-370, 2007) [2.] Global Environment Outlook GEO4, United Nations Environment Programme, 2007. [3.] Meliβ, M., Neskakis, A., Lange, C., Hövelmann, A., and Schumacher, J. (1998). “Wastewater Recycling Supplied by Renewable Energies: Basic Conditions and Possible Treatment Technologies.” Renewable Energy, Vol. 14 (1–4); pp. 325–331. [4.] Metcalf and Eddy, Inc., Eds. (1979). “Wastewater Engineering: Treatment, Disposal, Reuse.”Tata McGraw-Hill, Inc. [5.] Mushtaque Ahmed, Aro Arakel, David Hoey, Mark Coleman, Integrated power, water and salt generation: a discussion paper , Desalination 134 (2001) 37–45 [6.] Patil , Khanh-Quang Tran & Hans Ragnar Giselrød, Towards Sustainable Production of Biofuels from Microalgae, International Journal of Molecular Sciences, 2008, 9, pg 1188-1195 [7.] Ron Putt, Algae as a Biodiesel Feedstock: A Feasibility Assessment Center for Micro fibrous Materials Manufacturing (CM) Auburn University, Alabama, 2007 [8.] Sabbah et al, Green Appropriate Technologies For Wastewater Treatment & Reuse In The Rural Areas of The Middle East- Case Study Of Successful Regional Cooperation. [9.] Willie Driessen, Peter Yspeert, Yolanda Yspeert, Tom Vereijken, Compact Combined Anaerobic & Aerobic Process for the Treatment of Industrial Effluent, Environmental Forum. Colombia-Canada: Solutions to Environmental Problems in Latin America. May 24-26, 2000. Cartegena de Indias, Colombia [10.] Yusuf Chisti, Research review paper, Biodiesel from microalgae, Biotechnology Advances 25 (2007) 294–306

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