Effectiveness Of Biologigal Wastewater Treatment Environmental Sciences Essay

authority Of Biologigal Waste piss Treatment environmental Sciences EssayWaste piddle interposition is a serious environmental concern referable to the hazards of discharging poorly interact effluent to the environment. Poor savage piddle discussion poses a contaminant threat to receiving water bodies, groundwater defilement, soil contamination and impressioning loss of biodiversity (Mantila, 2002).Dandora E severalize Sewerage Treatment whole kit treats on average 62,000m3 per day annually of effluent from capital of Kenya metropolis and its adjoin with biological sermon and leave form the take sports stadium. The world targeted in this discover is effluent genuine and treated at DESTW.The purpose of this view is to find come on the potentiality of biological sewer water discussion and the pollution potential drop of DESTW activities to the environment.An experimental look into design go a port be recitationd to fructify the effluent characteristi cs and contaminant remotion small-arm a descriptive design result be employ to determine the environmental implications of effluent give-and-take.The instruments apply in the vignette ar observation, laboratory experiments, leopold matrix, network depth psychology, and repair characteristic outline. info analysis will be d wizard victimization both inferential and descriptive statistics. sewer water treatment has been defined as the process of removing contaminants from wastewater produced by both domestic help and industrial artificial lakes (Tchobanglous, 1993). Its objective is to produce treated effluent and sludge capable for discharge or reuse back into the environment which is achieved through and through physical, chemical substance and biological processes.The issue of wastewater treatment and disposal assumed increase importance in the early 1970s as a sequel of the general concern expressed in the United States and worldwide rough the wider problem of pol lution of the human environment, the contamination of the atmosphere, rivers, lakes, oceans, and groundwater by domestic, municipal, agricultural, and industrial waste (Oswald, 1996)A great deal of wastewater treatment plants ar separated all over the world and until recently not much scientific attention was given to these plants. They were considered to solve local problems so specific that one did not want to think it worthwhile to discuss design and performance of them in international fora.However, the interest shown for the 1st International Specialized assembly on Design and Operation of sewer water Treatment Plants (Trondheim, 1989), and the IAWQ Specialist congregation on the equal subject (formed in 1991), demonstrated that there is a need to discussion on international scale the strategies for planning and the expert development of much(prenominal)(prenominal) plants.The reason for this interest must be set in the abundance of cases slightly the world where sm all wastewater treatment plants have to be put in outgrowth to clog environmental pollution and hazards.There is a global shift from the traditional centralised wastewater treatment system to locally based wastewater solutions (Hallvard, 1993) side by side(p) the UN Decade for Water and Sanitation recommendations. The need for good solutions for wastewater treatment plants is therefore crucial in to a greater extent exploitation countries.Developed countries in general use mechanical and chemical treatment processes which though requiring less prop atomic number 18 very expensive to establish and maintain.Alabaster (1994) cites that many developing countries favour the use of biological treatment which uses wastewater stabilization ponds since mood favours its operation and it is a low-cost, low-maintenance, extremely effectual and natural method of wastewater treatment.The Dandora Sewerage Treatment Works (DESTW) which treats wastewater from capital of Kenya city and its environs uses biological treatment. However, due to stricter discharge standards set by National milieual Management Authority (NEMA), DESTW is increasingly falling short of those standards.Parr and Horan (1994) highlight tether principal reasons for wastewater treatment plants failure a lose of technical knowledge, failure to consider all applicable local factors at pre-design stage and inappropriate discharge standards.Mara (1992) cites the following broad impacts to the environment due to poorly treated effluent pollution of receiving aquatic water body, groundwater pollution from seepage of effluent, soil pollution from dumping sludge and wellness impacts from imbibition contaminated water or food grown by the same water.1.2 Problem StatementThe problem under investigation in this larn is the legalness of biological treatment in removing contaminants from wastewater and pollution potential of DESTW activities.Factors making the problem a critical issue to warrant reoc eanrch be the physical treatment unit at DESTW has not been useable for the past four years all pond serial publication unconnected from serial 3 and 5 lack anaerobic ponds closure of series 8 due to water hyacinth infestation may overload series 7 lack of pretreatment facilities in many industries that discharge into the capital of Kenya city sewer network may reduce treatment effectiveness and the environmental implications of groundwater pollution by effluent seepage and soil pollution by dumping of noxious sludge.Purpose of the StudyBased on the problem stated the purpose of this acquire is to investigate the effectiveness of biological treatment at removing contaminants from wastewater through empirical method of interrogation and propose sustainable methods of improving treatment effectiveness at DESTW.This see in addition aims at identifying the potential impacts to the environment resulting from DESTW activities and proposes methods of mitigating negative impac ts based on findings.1.4 Objectives of the StudyThe objectives of this study are as followsTo analyze the composition of wastewater received at DESTWTo analyze the effectiveness of contaminants mass remotion at DESTWTo determine the pollution potential in relation to activities of DESTWTo identify alternating(a) uses of treated effluent1.5 HypothesisThere is a positive kinship between the righteousnessing of biological treatment and the grapheme of effluent at DESTW.1.6 Significance and Justification of the StudyThis study addresses gaps in knowledge that come through in biological treatment effectiveness in treating wastewater from capital of Kenya, sewerage effluent has long been cited as the go of Nairobi River pollution, this study will quantify the extent to which effluent from DESTW pollutes the river.By addressing the above gaps in knowledge, the study will add to the body of knowledge in the field of wastewater treatment in Kenya.This study is important since the re sults will influence upcoming environmental policies on wastewater counsel, recommendations will propose sustainable methods commensurate for Kenya of further treating the effluent to get wind compliance with discharge standards, and they will in any case propose methods on improving existing methods of treating wastewater e.g. by product methane gas from anaerobic ponds to provide electrical energy for running the physical treatment works.The findings and recommendations will mitigate negative impacts to the environment as a result of DESTW activities.Beneficiaries from findings of this study are the community surrounding DESTW who will enrapture washed groundwater resources and decrease health risks from eating vegetables grown by effluent or eating fish caught from oxidation ponds.Downstream users of R. Nairobi will enjoy cleaner river water which will decrease prevalence of waterborne diseases.DESTW will benefit from this studys recommendations by increased environmental compliance and they will overly cut down on operational costs through generating electricity from anaerobic ponds methane gas. queryers will benefit from this studys findings which will form background teaching and methodology reference for future connect studies.Policy makers will use the findings and recommendations of this study in formulating policies for wastewater management in Kenya.1.7 Limitations and AssumptionsLimitationsLength of the study was limited to 3 months from January to March 2008 where data was to be collected. To overcome this limitation, data for previous years was obtained from the DESTW database.Breakdown of some laboratory machines hindered analysis of samples e.g. water distiller breakdown maintained analysis on some days due to lack of distilled water.Lack of a permanent vehicle at DESTW prevented final effluent sampling on some days.AssumptionsIt is assumed that the reagents were not contaminated.It is assumed that the criterion equipments were ca librated properly.It is assumed that sampling and storage cans were kept clean to prevent sample contamination.1.8 Study AreaThis study will be carried out at the Dandora Estate Sewerage Treatment Works (DESTW) which treats wastewater from Nairobi city and its environs using biological treatment process. The study area was elect since it forms a representative sample of Nairobi city waste wet. committeeThe startle phase was completed in 1977 and commissioned on 1978. The snatch phase was completed in 1990 and commissioned on 1992.LocationDESTW is fixed at Ruai in Embakasi division approximately 30km from the city center and rough 3km off Kangundo road. Access to the plant is on a permanent terra firma road. The site is approximately kilobyteha and the oxidation ponds are on 200ha.ClimateThe temper is a typical Nairobi climate with temperature ranging between 15-30 degrees centigrade. The average rainwater is approximately 760mm with the most of the rains falling in two seas ons, March to may (long rains) and October to December (short rains).Geology, soils and topographyThe geology of the area mainly dwell of Nairobi volcanics covered by black cotton clay soils. The area is generally flat with Nairobi River forming the north Eastern boundary of the land.Flora and savageThe area is generally arid with scanty vegetation cover, mainly sisal and shrubs. The ponds have attracted crocodiles and hippos from the nigh Nairobi River since they provide habitat and cheap source of food to for fauna and flora. Large colonies of different species of birds such(prenominal)(prenominal) as birds of prey (e.g., buzzard, golden eagle, and measuring stickn-owl), tend and woodland birds (e.g., pigeon, crow, and sparrow) water-birds and sea-birds (e.g., heron, swans, kingfisher, and curlew), and game birds such as quail hovered around the stabilization ponds during the day. Mudfish and tilapia fish have also been introduced in the maturation ponds to function in qual ity monitoring.Number of ponds and arrangementThere are a total of 38 waste stabilization ponds at DESTW which occur in 8 series. facultative and maturation (aerobic) ponds run in parallel. Only series 3 and 5 have anaerobic ponds.Types of pondsThere are tether types of ponds at DESTW and these areAnaerobic ponds- they are 4.0m deep and measure 100m by 100m. They are deigned for natural matter removal e.g. helminth eggs.Facultative ponds they are 2.5 m deep and measure 700m by 300m. They are intentional for BOD5 removal. festering ponds- they are 1.5m deep and measure m by m. They are designed for due north and phosphorus removal.Pretreatment and flow measurement facilitiesDESTW has a conventional ingestion works where large suspended solids are screened by coarse bar screens before being automatically raked by cup screens. mainstay is aim by use of constant velocity grit traps.A venturi gulch is provided for flow measurement.CHAPTETR TWO LITERATURE REVIEW2.1 Nature of eff luent2.1.1 strain and QuantityWastewater originates mainly from domestic, industrial, groundwater, and meteorological sources and these forms of wastewater are normally referred to as domestic cloaca, industrial waste, infiltration, and storm-water drainage, respectively(Mara, 1997).Domestic sewage results from peoples day-to-day activities, such as bathing, body elimination, food preparation, and recreation, averaging about 90 liters per person free-and-easy in Kenya (Asano, 1998). The quantity and character of industrial wastewater is highly varied, depending on the type of industry, the management of its water usage, and the degree of treatment the wastewater receives before it is laid-off.A typical metropolitan area discharges a volume of wastewater equal to about 60 to 80 percent of its total casual water requirements, the rest being use for washing cars and watering lawns, and for manufacturing processes such as food canning and bottling (WHO, 1992).2.1.2 CompositionThe co mposition of wastewater is analyzed using several physical, chemical, and biological measurements. The most common analyses accommodate the measurements of solids, biochemical type O demand (BOD5), chemical oxygen demand ( fluff), and pH (Pena, 2002). The solid wastes include wriggle and suspended solids. Dissolved solids are the materials that will pass through a filter paper, and suspended solids are those that do not.The concentration of thorough matter is thrifty by the BOD5 and COD analyses. The BOD5 is the amount of oxygen used over a five-day period by microorganisms as they decompose the thoroughgoing matter in sewage at a temperature of 20 C. Similarly, the COD is the amount of oxygen required to change the organic matter by use of dichromate in an acid solution and to convert it to snow dioxide and water. The value of COD is always higher than that of BOD 5 because many organic substances can be oxidized chemically just cannot oxidize biologically (Curtis, 1992) .Commonly, BOD5 is used to test the strength of untreated and treated municipal and biodegradable industrial wastewaters. COD is used to test the strength of wastewater that is either not biodegradable or contains compounds that inhibit activities of microorganisms.The pH analysis is a measure of the acidity of a wastewater sample.2.2 Biological Wastewater Treatment2.2.1 Waste Stabilization Ponds Technology OverviewWaste stabilization ponds (WSPs) are usually the most appropriate method of domestic and municipal wastewater treatment in developing countries, where the climate is most favourable for their operation WSPs are low-cost (usually least-cost), low-maintenance, highly efficient, entirely natural and highly sustainable (Alabaster, 1994). The only energy they use is direct solar energy, so they do not need any electromechanical equipment, saving expenditure on electricity and much skilled operation. They do require much more land than conventional electromechanical treatment processes such as unrestrained sludge but land is an asset which increases in value with time, whereas coin spent on electricity for the operation of electromechanical systems is gone forever).WSP systems comprise one or more series of different types of ponds. Usually the first pond in the series is an anaerobic pond, and the assist is a facultative pond. These may need to be followed by maturation ponds, but this depends on the required final effluent quality which in turn depends on what is to be done with the effluent used for restricted or open-ended irrigation used for fish or aquatic vegetable culture or discharged into surface water or groundwater (Horan, 1994).Prior to treatment in the WSPs, the wastewater is first subjected to preliminary treatment screening and grit removal to remove large and heavy solids.Basically, primary treatment is carried out in anaerobic ponds, secondary treatment in facultative ponds, and tertiary treatment in maturation ponds. Anaerobic and facultative ponds are for the removal of organic matter (normally expressed as biochemical oxygen demand or BOD), Vibrio cholerae and helminth eggs and maturation ponds for the removal of fecal viruses (especially rotavirus, astrovirus and norovirus), faecal bacteria (for example, Salmonella spp., Shigella spp., Campylobacter spp. and pathogenic strains of Escherichia coli), and food for thoughts (nitrogen and phosphorus). Due to their high removal of excreted pathogens, WSPs produce effluents that are very suitable for reuse in agriculture and aquaculture.2.2.2 Related investigate on Biological Wastewater TreatmentMandi (1993) in his comparative study of Wastewater treatment by stabilization ponds with and without macrophytes under arid climate found that ponds using water hyacinth proved most efficient than those using microphytic plants (algae). Howver, the process based on water hyacinth for wastewater purification is faced with two major problems first the water loss by e vapotranspiration reaches 60% during spend time and secondly the development of mosquito during summer time.He however does not address the huge quantities of biomass produced from water hyacinth treatment systems and the resulting increase in sludge deposition rate.Ghrabi (1989) in his experimental study Treatment of wastewater by stabilization ponds application to Tunisian conditions concluded that sediment accumulation occurs mainly in the first pond the deposition rate is high (5 cm/year). In the maturation ponds, it ranges from 1.3 cm/year to 1.6 cm/year. The first pond can be desludged per year or once each two years.He however in his study doesnt mention the environmental impacts of sludge to the soil and he also doesnt suggest methods of decreasing the amounts reaching the wastewater stabilization ponds.Jensen (1992) in his study on the Potential use of constructed wetlands for wastewater treatment in Union environments concluded that wetlands achieve 98% phosphorus remov al, 88% BOD removal and 55% nitrogen removal respectively. COD removal was only 64% due to discharge of organic matter that is slowly biodegradable e.g. humic acids.This study however didnt estimate the productive lifespan of the constructed wetlands.2.3 Problems in Wastewater Treatment and Disposal2.3.1 Wastewater Treatment Plant ProblemsMany wastewater treatment plants (WwTP) of all kinds in developing countries do not function properly. Parr and Horan (1994) found that there are three principal reasons for WwTP failure a lack of technical knowledge failure to consider all relevant local factors at the pre-design stage and inappropriate discharge standards. As a result, wrong decisions are often do and inappropriate unsustainable treatment processes are selected and implemented. This is then exacerbated by the absence of any real incentive to shut away the WwTP correctly once it has been commissioned. It is therefore essential for the long-term sustainability of WwTP that simple efficient technologies such as WSPs are always considered at the pre-design (or feasibility) stage. An honest equation of the cost-effectiveness of wastewater treatment technologies will almost always favour the plectron of WSPs in warm-climate countries.2.3.2 Environmental Problems of Wastewater Treatment and DisposalIf wastewater is discharged before it is properly treated, it can waywardly affect the environment, public health and destinations economic well-being. The cost of these negative impacts can be expressed in monetary, health and ecological terms (Mara, 1997).Mantila (2002) identifies a number of consequences of poorly treated wastewaterHealth Impacts from pathogenic bacteria, viruses and toxic algae cause diarrhoea, mollusk poisoning and other diseases bathing in polluted water causes stomach flu and upper respiratory diseases eating polluted shellfish results in hepatitis, liver-colored damage and in some cases death.Impact on Marine Environment in the form of sus pended solids may cause excessive turbidness and shading of sea grasses, produce sedimentation, damaging benthic (bottom layer) habitats and affect anaerobic conditions at the sea bottom high BOD levels may cause severe oxygen depletion especially in shallow and enclosed aquatic systems such as estuaries that are ideal breeding grounds for respective(a) marine species resulting in fish deaths and anaerobic conditions which release bad odors(hydrogen sulfide) adverse nutrient levels cause algal blooms, resulting in the death of coral and sea grasses and eutrophication leading to severe oxygen depletion which kills living resources many toxic materials and guess carcinogens and mutagens can concentrate in fish tissue, putting humans at risk when they eat them metals in specific forms can be toxic to humans and various marine organisms especially shellfish which is vulnerable, in areas with highly contaminated sediment layers fats, oil and grease that float on the water surface inter fere with natural aeration, are possibly toxic to aquatic life, destroy coastal vegetation and reduce recreational use of waters and beaches.Impact on Groundwater and Water Resources in the form of improper disposal of wastewater can directly impact the quality of an areas groundwater and water resources and since their movements are dynamic, contaminants can spread far beyond the immediate pollution area.2.4 Wastewater Management OptionsOswald (1995) states that the following issues should be addressed before designing an effective wastewater management plan assess current wastewater management practice before water is discharged to the municipal treatment facility, realisation of sources of wastewater, determine whether discharged wastewater quality meets effluent standards, identify whether industries be given out pre-tretment of their wastewater and finally assessing complaints from users of reclaimed wastewater effluent. Once the seat has been assessed, a range of approaches and techniques to deal with wastewater can be considered.Bartone (1996) argues that to ensure effective treatment o wastewater, the volume has to be reduced to prevent overloading of wastewater treatment plants and this can only be achieved at the source through installation of water efficiency equipment e.g. ultra-low flush toilets, spray nozzles, low-flow showerheads, water spigots, all which reduce overall water consumption.Collection of domestic wastewater and transportation to a distant treatment plant is a operose and highly expensive task, if the catchment area to be served is low in population density (Tchobanoglous, 1993). Onsite treatment of sewage is the alternative and has been applied al around the world for many centuries.However, purification achieved by traditional onsite treatment systems such as septic tanks (DIN, 1993) is rather poor especially with respect to nutrient removal and as a result impacts on the quality of groundwater are inevitable.The basic idea of the biofilter septic tank was introduced by Toshio Yahata (1981) and further developed by Stubner and Sekoulov (1987). The biofilm reactor septic tank has been found to be more efficient (Robert, 1996) and effluent can be reused for irrigating or flushing toilets.2.5 Conceptual role modelThis study is based on the conceptual mannequin below that aims at optimal use of resources in an environmentally sustainable manner.Stage commentaryThe main sources of generation are households, commercial and industrial sources.This is done through the sewer network in Nairobi and conveyed to DESTW. An annual average of 62000 m3 wastewater reaches DESTW dailyIt aims at screening solids and grit removal from wastewater stream. rough bar screens- remove large suspended solidsMedium bar screens remove smaller suspended solidsCup screens- remove finer suspended solidsGrit traps- remove grit and sand particles from wastewaterInvolves use of wastewater stabilization pondsAnaerobic ponds are designe d for organic matter removalFacultative ponds- are designed for BOD removalMaturation ponds- designed for nitrogen and phosphorus removalTreated effluent disposed of in Nairobi RiverEffluent reused for agricultural irrigation and livestock watering.Fig 1 Conceptual framework for wastewater treatment and disposal in Nairobi.(Adapted from WHO,1992)CHAPTER THREE METHODOLOGY3.1 Research DesignThe design used in this research is experimental since analysis of wastewater quality is done in the laboratory.It is also descriptive since the state of the environment and biological treatment process are described.The approach used in this study is deductive since it begins with the perceptual experience and observation of an environmental problem, leads to hypothesis formulation, experimental design, data collection, statistical analysis, theory construction, and finally to explanation.3.2 tribe and SamplePopulationThe population targeted in this study is the wastewater received and treated at DESTW which averages 62,000m3 per day annually.Sample typesGrab samples were necessary for parameters such as pH, ammonia, and faecal indicator bacteria.Flow-weighted composite samples were necessary for raw sewage parameters such as electrical conductivity, dissolved oxygen,Frequency of sampling novel sewage was sampled periodical because its composition varies considerably throughout the day.Flow was sampled hourly throughout the day.Final effluents were sampled once daily before noon.Pond series were sampled once every week.Nairobi River upstream and downstream was sampled once a week.Data Collection Instruments3.3.1 Field ObservationEnvironmental impacts will be identified using field observation which will be aided by the following instrumentsa) Leopold matrixIt is a grid-like table that is used to identify the interaction between roam activities, which are displayed along one axis, and environmental characteristics, which are displayed along the other axis. Using the table , environment-activity interactions can be far-famed in the appropriate cells or intersecting points in the grid. Entries are made in the cells to highlight impact severity or other features related to the nature of the impact, e.g. numbers in this study are used to demo scale in this study.This instrument was chosen for environmental impact realisation because it links the action to the impact, shows impact magnitude and significance, and is a good way of displaying environmental impact results.b) Network analysisNetworks illustrate the cause-effect relationship of project activities and environmental characteristics. They are, therefore, particularly useful in identifying and depicting secondary impacts ( corroboratory, cumulative, etc). They are drawn by identifying first order impacts first then linking them to second order impacts and third order impacts by use of an arrow.This instrument was chosen for environmental impact identification since it links the actions to the im pacts, is useful I modify form for checking for second order impacts and can handle direct and indirect impacts.c) Impact characteristics analysisIt is normally in the form of a summary table and this instrument was chosen for environmental impact identification because it shows impact nature, magnitude, extent/location, timing, duration, reversibility, likelihood (risk), and significance.3.3.2 Laboratory experimentsExperiments were performed to determine the composition of wastewater at DESTW and the mass removal of contaminants from the wastewater. The apparatus below will be used during the laboratory experimentsPlastic sampling cans were used to collect and store samples.A wooden pole with 1cm graduations was used to measure depth at the venturi flume.A refrigerator was used to store samples at below 4 degrees Celsius.Burettes, conical flasks, pipettes, beakers, and digestion thermionic vacuum tubes were used to hold samples and reagents when analyzing for various parameters in the laboratory.Ovens, digestion blocks, water baths, and fume chamber were used in creating conducive conditions for chemical reactions to take place in the laboratory.Pan balances, beam balances, UV spectrophotometers, atomic absorption spectrophotometers, water quality meters and flame photometers were used to measure values of various parameters in the samples.3.4 Data Collection offices3.4.1 Laboratory Analysis ProceduresParameters will be analyzed agree to Alabasters 1989 Practical Guide to the Monitoring of Waste Stabilization Ponds standard operations manual that was adopted by the DESTW laboratory.a) FlowThis will be measured on the raw sewage and final effluents using the venturi flume which is a restriction in the channel carrying wastewater. The formula below was used to picture flow.Q =23 2/3 g CV.CD . b. h3/2Where Q= flowrate m3/s CV = coefficient of velocityCD = coefficient of discharge b = width of pharynx (m)h = upstream depth (m)b) COD total and filteredThe micro-digestion sealed tube method will be used with potassium dichromate as digestion solution and ferrous ammonium sulfate as titration solution.Procedure1.5 ml of digestion solution is dispensed into a digestion tube, 2.5 ml of sample is added using a pipette and mixed well, 3.5 ml of catalyst solution (silver sulphate in 2.5 liters of sulphuric acid ) is added, the tube is capped tightly using a PTFE sealing gasket, the tubes contents are then mixed by quell swirling, the tubes are then placed in a digestion block at 1500 C for 120 minutes, contents of the tube are transferred quantitavely to 100ml conical flask and sufficient water added to a final volume around 25 ml , 1 drop of ferroin indicator is added and the solution mixed well, it is titrated with FAS (N/40) until the wakeful blue colour changes to red and the value of the titre T ml recorded, a blank titration is carried out following the same procedure but using distilled water instead and the value of blank titre B ml recorded.COD calculated as follows COD = (B-T) / S - 1000 mg/lc) BOD totalThe standard 5 days, 20 0C, BOD bottle test will be used.ReagentsDilution water, ferric chloride solution, manganous sulphate solution, sodium azide solution, alkali- iodide solution, 90 % orthophosphoric acid, N/40 sodium thiosulphate, starch solution.ProcedureDilution water is prepared, sample added and incubated at 200C for 5 days to determine dissolved oxygen, remove stopper from the BOD bottle and 2ml each of manganous sulphate solution, sodium azide solution, alkali- iodide solution, immediately after the addition of alkali-iodide reagent a brown flocculent effectuate forms therefore the bottle is shaken to ensure that all the dissolved oxygen reacts with the reagents, when the floc settles add 2ml orthophosphoric acid and shaken until the bottle contents turn yellow, 205 ml of the bottle contents is titrated with N/40 sodium thiosulp