Nitrification Process in Landfill Leachate Treatment

Nitrification Process in Landfill Leachate TreatmentCHAPTER 1INTRODUCTIONoerviewLandfilling is superstar of the oldest and vernacular methods utilize for thieve giving medication. It is perceived as the most economical and environmentally acceptable technique. It is a complex arrangement with physical, chemical, and biologic figure go forthes.While lowgoing the lick of wastes degradation, there is the production of utmostly contaminating smooth, leachate, and polluting screw upes. If f reed in an undisciplined and non-engineered manner, leachate allow contaminate ground irrigate bodies and subsequently jeopardizing the ecosystem. in that respect is a network for the gathering the contaminants. The gases such as methane and hundred dioxide be fl bed before they derriere need the atmosphere. The leachate generated, requires intercession before discharge and it is the main difficulty.In Mauritius, there has been an surge in the metre of wastes generated due t o rapid industrialization. A structure for immobile waste man yearsment was necessitated which dissolvered in the construction of Margon Chicose Sanitary Landfill Site. oer the years, there has been an increase the heap of wastes cosmos disposed and consequently, a facelift in the descend of leachate generated.As previously mentioned, the polluting liquid requires interposition foregoing to administration. Nowa twenty-four hourss, we do contain laws that ar regulated by the Waste peeing charge Authority Act and the organization operates down the stairs the aegis of the Ministry of general Utilities. aft(prenominal) intercession leachate shall comply with the standard limits for effluent discharge as shown in Appendix C.Many studies have been carried out for the discourse of leachate and conf hired methods be available. in that location are some(prenominal) parameters that define the handling method. The treating technique shall be effective, cost-effective with minimum input, flexible and if possible usage of the effluent.Aim and ObjectivesThe scram of the project is the study of the nitrification butt in the intercession of landfill leachate.The project had the hobby objectives setTo determine the suitability and potentiality of a SBR and co intercession method for the intercession of landfill leachate.To find the tightfistedness at which ammonia northward is toxic to microorganisms.To physical body a suitable tank for the method existence espouse.To assess the cost-effectiveness of the treating systemStructure of ThesisThe remainder of this thesis is organized as followsChapter 2 keep backs a brief overview of landfilling process, describing the various components of a landfill. there is a description of the Mare Chicose Sanitary Landfill Site and a sum-up of typical leachate effluent.Chapter 3 deals with the treating options available for effluent treatment particularly leachate. The efficiency for ammonia normality r emoval is outlined and a reviewing well-nigh occurrence studies on biological treatment of landfill leachate.Chapter 4 describes the methodology adopted for leachate treatment.Chapter 5 gives a detailed analysis of the results obtained and assessment of various parameters.Chapter 6 consists of the design a treating system for leachate.Chapter 7 describes the cost effectiveness of the treatment methods and some recommendations for improvement of the designs.CHAPTER 2REVIEW of LITERATURE2.1. LandfillA landfill may be defined as a physical facility utilise for the disposal of residual solid wastes in the surface soils of the earth (Tchobanoglous et al.). Nowadays, the term sound landfill is more(prenominal) usually utilized to describe an engineered facility, designed, operated and monitored with the foremost objective of standard-down environmental and health hazards.According to Tchobanoglous, a landfill may be reason with respect to the incoming waste corporeals.There are various criteria that are considered before the design and construction somas. The situation merchant shipnot be close to water bodies, gamyways, any residential areas or even airports. The main reason is the contaminant accompanied by the operation of such a rate which volition eventually disturb its surrounding environment.An opposite factor is the hydrogeology of the site, groundwater maps are vigilant by studying the different soil stratum. This helps in determining the permeableness of the soil, the depth to groundwater, the direction of groundwater menstruation and hydraulic gradients. If clay is to be apply as a liner, then borrow sources are found.Landfill ComponentsLiner It is a barrier that will prevent the leachate and new(prenominal) liquids from penetrating the soil. It endure be made of clay, synthetic materials or both which is known as multiform liner. This barrier to a fault restricts the underground migration of landfill gases.Cap system Usually a s oil dwell hardened over the landfill at completion of filling, similarly known as final cover, with vegetation grown over it. The cover may consist of geosynthetic materials also, thus hindering the escape of landfill gases to the air and constricting the infiltration of rain into the landfill (Bagchi, 1994).Gas management system As shown in the diagram to a higher place, these are a series of gas wells that use ups methane and other decomposition gases from the landfill for flaring and reuse. The methane gas may be employ in the electricity production.Leachate management system A issue of horizontal and perpendicular pipes placed just above the liner that drains and collects leachate. later onwards the polluting liquid may be brought to a retention pond.Mare Chicose Sanitary Landfill SiteOver the last few years, a rapid development at socio-economic aims has brought an pot in the come in of wastes generated in Mauritius. There was a need for an merged solid waste mana gement programme.The Mare Chicose Sanitary Landfill is the only waste disposal site for Mauritius till date. The site is located in the Confederate part of the island near a picayune village called Cluny. It receives mostly municipal solid wastes and accordingly categorized as a Class type.The site was previously operated by STAM Lte, from 1997 to 2006, and presently by Sotravic Limite/ Bilfinger-Berger consortium. The amount of wastes disposed at the landfill has nearly tripled over the years, reaching to a fooling value of about 1,200 tonnes.The percentage of incoming wastes is summarized belowThe field capacity of the landfill was already attained and currently there is an extension of works on existing cells. The site is comprised of six cells and actually the fifth one is in use.Prior to disposal at the landfill, the wastes are compacted at transfer stations. The wastes are dumped from a tipping point and soon, they are spread over existing wastes by nitty-gritty of speci alized vehicles. At the end of the day, a cover is placed to reduce the amount of windblown debris.Both clayey and geosynthetic liners were used on the site. The amount of leachate being carted away for the period of January 2007 December 2007 is 110 858 m3. Actually, no leachate treatment is being carried out. Among the landfill gases produced methane is the most dangerous and it is dealt with in a controlled environment. The gas is being unruffled by means of pipelines and subsequently flared.LeachateThe definition fit to EPA is as followsWater that collects contaminants as it trickles by means of wastes, pesticides or fertilizers. Leaching may occur in farming areas, feedlots, and landfills, and may result in savage substances entering surface water, ground water, or soil.Leachate dirty dog be depict as a super contaminated liquid, containing a considerable amount of dissolved and hang solids that has percolated down through wastes. The leachate quality varies throughout the working(a) vivification of a landfill and long after(prenominal) its closure. There are terce broad and overlapping grades of waste decomposition, in which chemical and biological processes give rise to both landfill gas and leachate during and beyond the active life of the site (Carville et al.).Phase 1 Oxygen present in the wastes is rapidly consumed by aerobic decomposition. This phase has duration of less than one month and is ordinarily relatively unimportant in terms of leachate quality. This phase is exothermic and high temperatures may be produced. If some of this heat is retained, then as a result of that the rate of the upcoming phases is increased.Phase 2 Anaerobic digestion is comprised of the pas conviction four phasesHydrolysis A chemical re sue where thumping polymers are born-again to simple monomers.Acidogenesis A biological answerion where the monomers are converted to volatile fatty acids.Acetogenesis A biological reaction where the fatty acids ar e converted into hydrogen, blow dioxide and acetic acid.Methanogenesis The acetic acid is converted into acetates. Hydrogen is used up to convert the acetates into methane and carbon dioxide.Anaerobic and facultative microorganisms hydrolyze cellulose and other perishable materials such as complex carbohydrates, fats and proteins to soluble fundamental compounds. These hydrolysis products are then fermented during acidogenesis to various intermediates such as volatile fatty acids and alcohols. Finally, these intermediates are converted during acetogenesis to acetic acid, carbon dioxide and hydrogen. The high content of putrescible material in the waste may sustain acidogenic conditions for sort of some time and raise a rich feed stock for methanogens subsequently. Leachate from this acidic phase typically contains a high niggardliness of free fatty acids. It therefore has low pH of 5 or 6, and will dissolve other components of the wastes, such as the alkaline earths and heavy metals, which give notice be mobilized in the leachate, possibly as fatty acid complexes. The leachate also contains high tightfistednesss of ammoniacal atomic number 7 and has both a high organic carbon parsimony and a biochemical oxygen demand (BOD).Phase 3 Conditions wrench more anaerobiotic as waste degradation proceeds and methanogenic bacteria gradually become established. These start to consume the simple organic compounds, producing a mixture of carbon dioxide and methane that is released as landfill gas. The carbon dioxide tends to dissolve producing the genuinely high bicarbonate concentrations typical of Phase 3 leachates. The rate at which this phase becomes established is controlled by a number of factors, including the content of readily putrescible waste. Since the majority of the organic compounds are high molecular weight humic and fulvic acids, the leachates are characterized by relatively low BOD values. Ammoniacal north continues to be released by areas of the waste where phase 2 is continuing and chiefly remains at high concentrations in the leachate. Falling redox voltage immobilizes many metals as sulphides in the waste.(Source www.wikipedia.com/leachate)Typical leachate effluentLeachate is usually termed as a high strength effluent. The polluting liquid has a high concentration of contaminants and varies throughout the landfill age as shown in the table below.From the above table, it observe that leachates are normally alkaline having a pH of 6.0-8.4. The average catch value is found to be 5000 mg/l and the ammoniacal nitrogen remains in spite of appearance a similar range 900-3000 mg/L for all most of the sites.As it has been portrayed, the leachate does not meet the requirements for discharge any in sewers or surface water (see Appendix C) and this clearly indicates a need for treatment.CHAPTER 3Treatment OptionsOverviewMost landfills operate their own onsite leachate pretreatment and treatment facilities. Three types of treatment are possible physical, chemical and biological. Usually they are used in conjunction with one another.The constituents of leachate and availability of resources determine the treatment method to be adopted. Therefore, it should be efficient, flexible and an economical option.The leachate quality is highly dependent on the waste materials being disposed and the stage of their anaerobic decomposition. Hence, there is a variation in the constituents concentration.It has been observed that throughout the life cycle of a landfill, the ammonia nitrogen concentration remains very high. Amongst several usual parameters, ammonia nitrogen is a key one as it influences the selection and the design of the treating system.Physical TreatmentAmmonia strippingAmmonia can be withd stark naked by the air stripping technique which consists of blowing air through the wastewater. The method is based on the chase equationThe above equation is highly dependent on the pH so that an exchang e of ionic forms can take place. The equilibrium eternal for this reaction is 10-9.25 at 18 C (Sorensen, 1993).pH = 9.25 + log NH3 / NH4+From the above equation a pH great than 10 is needed for evacuant the ammonia gas. At normal temperature only 2% of the gas is liberate and therefore the wastewater should be heated to increase the efficiency of the treatment process.In achieving relatively low effluent values of ammoniacal-N (e.g. Reverse OsmosisThe process consists of applying a pressure to the wastewater, i.e. the leachate, which passes through a semi permeable membrane. The water molecules present in the wastewater will pass the membrane forming the disperse and the contaminants remaining are the concentrate.The main advantage of using such a system is the removal of non-biodegradable compounds such as residual apply, heavy metals and chloride ions in concert with other large molecules present in leachate.The concentrate produced is a major issue as it is highly toxic to t he environment. It is usually recirculated in the landfill or disposed off-site for storage.The removal rate of the contaminants is usually greater than 99.6 %. The whole caboodle is usually operated in more than one stage and occupies less space when compared to other treating systems. The process is currently in use in several countries such as France, Germany and Holland (IPCC, 2007). worked up Carbon AdsorptionActivated carbon is used as an adsorbent for the removal of organic compounds. It is used in one of the undermentioned forms, powder and gamey. Due to the high cost of trip carbon, it is normally utilized for polishing after biological treatment. With an optimum venereal disease and commensurate contact time, a considerable decrease in COD and BOD concentration can be achieved by this method.In the powdered form, the carbon is meant for single use and it loses its adsorption capacity and therefore cannot be reactivated. The mixed liquor moldiness then be treated to remove the PAC, by subsequent processes, such as coagulation, flocculation, or filtration.In the granular form, the carbon can be used again but must be removed which requires specialized equipment (IPCC, 2007). biologic Treatment ProcessesThe treatment process is comprised of growing and reproducing microorganisms in a controlled environment to stabilize organic matter. There are two forms of growth process attached and hang. In suspended growth treatment systems, microorganisms are maintained in suspension within the wastewater whereas in the attached growth process, the biomass grows and is retained on a medium.Attached Growth ProcessesPercolating filtersRotating biological Contactors (RBC)Suspended Growth Processes expose lagoonsActivated max Process (ASP)Sequencing Batch Reactor (SBR)Combined treatment with home(prenominal) wastewater (co treatment)Percolating FiltersIt is an aerobic biological treatment system. sewer water mensess over a fixed and inert medium to which biofilms are attached and trickles down under gravity. The medium may be made up of different materials such as plastics and gravels and the depth of the filter is normally 2-4 m. The effluent is passed through a clarifier to remove biological solids.The percolating filter has many disadvantages concerning the treatment of landfill leachate. The system is efficient mostly for the treatment of low strength leachate. A recurrent problem is the clogging of the filter media and vulnerability to shock-term load (IPCC, 2007).Rotating Biological ContactorsThe process consists of large diameter steel or corrugated plastic media centered slightly a horizontal shaft, usually placed in a cover tank. The media is slowly rotated (mechanical or air drive). At any accustomed time during the rotation, about 40% of the media surface area is in the wastewater. Organisms in the wastewater are attached and, multiply on the rotating media until they form a thin layer of biomass.RBC is most effective for treating methanogenic than acetogenic leachates and for concentrations of ammoniacal-N below 500mg/l. The rotating biological contactor may have operational problems, since high concentrations of degradable COD can result in excessive sludge growth, and clogging of interstices within rotors (IPCC, 2007).Aerated LagoonsAerated lagoons are operated by a combination of aerobic and anaerobic processes. The take down part of the lagoon converts the settled solids and sludge into carbon and methane by the action of anaerobic decomposition. The upper part is usually aerated, surface aeration or by algae present, to oxidize compounds from the anaerobic zone.Effluent is withdrawn from the upper zone, mostly over an overflow arrangement. For discharge into surface waters, a secondary colonization lagoon or reed bed filtration system is needed for wastewater polishing.The constraints of the system are as such it requires large space and is quite sensitive to temperature changes. There i s the possibility of odurs emanating from the lagoon. The main concern is the inability to provide consistent and reliable design in order to meet the discharge limits.Activated Sludge ProcessIt is the most widely used aerobic biological process for treatment of domestic wastewater. It operates on the basis of a continuous inflow of wastewater. The latter is completely mixed and aerated for genuine period of time, giving rise to mixed liquor. For nitrification to occur the sludge age must be greater than 8 days, so that the nitrifying bacteria can grow sufficiently large in numbers to exert an oxygen demand. The mixed liquor is allowed to settle in the clarifier and the biomass is returned to the aeration tank. The clarified effluent is swarmed for disposal or tertiary treatment. The ASP is a continuous process and leachate cannot be treated directly, it requires dilution due to ammonia toxicity.Sequencing Batch ReactorThe reactor is a slight modification of the ASP. It operates on a fill-and-draw basis using the suspended growth process. The SBR utilizes a single tank which accommodates aerobic biological treatment, flow equalization, settlement of solids, effluent clarification and decanting. and then, it is usually described as operational in time rather than space when compared to conventional ASP.The reactor consists and operates under the following cyclesFill During the fill operation, volume and substrate (raw wastewater or primary effluent) are added to the reactor. The fill process typically allows the liquid take aim in the reactor to rise from 75% of capacity (at the end of light period) to 100%. During fill, the reactor may be mixed only or mixed and aerated to promote biological reactions with the effluent wastewater.React During the react period, the biomass consumes the substrate under controlled environmental conditions.Settle Solids are allowed to separate from the liquid under quiescent conditions, resulting in a clarified supernatant that can be discharged as effluent.Decant Clarified effluent is removed during the decant period. Many types of decanting mechanisms can be used, with the most popular being floating or adjustable weirs.Idle An gaga period is used in a multitank system to provide time for one reactor to complete its fill phase before switching to another unit. Because idle phase is not a demand phase, it is sometimes omitted.Advantages of the systemIt requires small space as a common tank is used for the various unit processes.Flexibility in operating the reactor.The reaction time can be controlled and settling can be achieved under quiescent conditions.There the elimination of the return sludge pumping when compared to the ASP.Disadvantages of the systemA higher aim of sophistication is ask (compared to conventional systems), especially for larger systems, of timing units and controls. possible of discharging floating or settled sludge during the draw or decant phase with some SBR configuration s.Combined Treatment with Domestic sewer waterIt is a combined method for treating domestic wastewater and landfill leachate. Both wastewater and leachate can be treated at suitable mixing ratios (Aktas, 2001). Domestic wastewater can provide phosphate while leachate can provide nitrogen based nutrients, thus compensating for nutrients deficiency. Hence, nutrients need not to be supplied.Leachates from older landfills have a lower BOD/COD value and a smaller biodegradable organic fraction. There may not be sufficient COD to support denitrification of nitrate, a supplementary source of organic carbon is required to ensure adequate denitrification. Synthetic chemicals, such as wood alcohol or acetic acid, are effective but quite expensive. It is inevitable to find an alternative cost effective source of easily biodegradable carbon (Zhang, 2005).The mixing ratios are determined or else there will be nitrification inhibition by the presence of excess free ammonia. field of study stud ies for biological treatment of landfill leachateThe Buckden Landfill Site has been operational since 1994 and has been successful in treating landfill leachate for more than 10 years. The landfill site uses twin sequencing batch reactors, each designed for treating up to 100 m3/day. The effluent is then treated by means of reed bed and an ozonation do for wastewater polishing and removal of pesticides.The plant has a design loading rate of 0.02 0.040 kg N/kg MLVSS. The plant has been successful in removing ammonia nitrogen from 331 mg/L to 0.27 mg/L. Only the COD value has not met the discharge limits (The main tally costs are due to electricity for aeration and for ozonation. There is also the use of sodium hydroxide for automatic pH control, and of phosphoric acid for planning of phosphorus as a nutrient, which are relatively small costs. some other case is a South-African landfill which receives up to 2000 tonnes of MSW each day. Up to 80 m3/day of leachate are generated, wh ich have to be treated to very high standards. The treatment system is made up of a SBR with final polishing through a reed bed planted with Phragmites. The SBR is highly efficient for ammoniacal nitrogen removal from over 1200 mg/l to less than 1.0 mg/l. COD values are reduced by 60% from raw leachate values of over 2000 mg/l (Robinson et al., 2005).CHAPTER 4MATERIALS AND METHODS4.1. OverviewThis chapter deals with the methodology adopted and is comprised of the following phasesSamplingSample preservationWastewater characterizationLeachateWastewater from SMTPSludgeBiological treatment of landfill leachate using a SBRCo-treatment of landfill leachate with wastewater from SMTPexaminationResults and analysisConclusionsSamplingSampling is done to represent a real population, in this case wastewater, on which tests are performed and the results symbolize the wastewater characteristics. This can be achieved by two methods composite sampling and arrest sampling.A composite sample consis ts of collecting samples at regular interval in time. This will be representative of the average wastewater characteristics.A overtake sample is based upon obtaining a distinct sample regardless to its flow or time of the day.If the wastewater quality is not highly variable, the results obtained from grab sampling will tend to corroborate composite ones. Both methods are used and for this project the grab sampling technique was adopted.Sample preservationSoon after the samples were collected, they were tested and if not possible, they were continue. The latter is crucial step as most of the wastewater constituents have to be kept as are in their original state. They were incubated at 4 C and when necessary pH control was done by adding sulphuric acid. Subsequently, this will ruin all the biological activities.Wastewater CharacterizationThe next step after sampling is characterization, i.e. determining the level of constituents present in the wastewater. As a fact of that, the trea tment method is selected and applied to the polluting material. Each time, when new samples were obtained, they were characterized in compliance with Standard Methods of Testing.For the project, characterization has to be done for these materialsLeachateThe leachates were delivered at the UOM Public wellness Laboratory, on the 23rd October 2007 and 9th January 2008, and were characterized for the main polluting parameters. Then the sample was preserved till the treatment starts.Domestic WastewaterThe domestic wastewater was collected at SMTP. The sample was collected from the primary clarifier after degriting has been done on the following dates 26th February and 3rd March 27, 2008. The samples were immediately characterized and then used.SludgeFor nitrification to take place there should be microorganisms feeding on the organic matter, but leachate does not contain any. Therefore, the returned sludge from SMTP was collected and brought to the UOM Public Health Laboratory. The sludg e was allowed to settle and the supernatant was discarded, the residual left was used for testing. As a result of that the sludge concentration was increased and smaller amount is required for biological treatment. A TSS was carried out and the value obtained was used for calculations. The sludge was also studied under the microscope determining the microorganisms present and their conditions.Biological Treatment of Landfill Leachate using a SBRThe branch option for treating leachate was the biological treatment by making use of a SBR. It was made up of the following phases fill, react, settle and decant. The reactor consisted of sludge, water and leachate with varying composition. Their volumes were calculated such that the ammonia nitrogen concentration is about 50 mg/L in the reactor. The latter was aerated for a period of 24 hours. The main polluting parameters were monitored and accentuating upon the level of ammonia nitrogen and nitrate nitrogen. The system was run for a numb er of cycles and then denitrification phase was operated.Experimental ProcedureA reactor of capacity 20 L was considered with an MLSS concentration of 4000 mg/l. The dissolved oxygen concentration had to be greater than 2 mg/l and this was achieved by the means of air diffusers. The diffusers provided the mixing within the reactor.Immediately after the setting out of the reactor, a grab sample was collected and was tested. These values were set as baseline.After 24 hours of aeration, another sample was collected from the reactor and tests were performed. The captious parameter i.e. ammonia nitrogen was observed and if, the value is not within the discharge limits then it aerated till the expected result is obtained.The biomass required nutrients which provided in the form of Potassium Hydrogen Phosphate.In order for the treatment to take place, we had to cater for alkalinity and this was achieved by the addition of concentrated sodium hydroxide.Thus the nitrification process was be ing monitored until no further treatment.A total of 3 sequential batch reactors were operated.After the operation of the third reactor, the denitrification phase was initiated. completely the air diffusers were switched off and acetic acid was added to the reactor.The dissolved oxygen concentration was monitored till it reached the zero value and the nitrate nitrogen concentration was measured.Co-treatment of Landfill Leachate with Wastewater from SMTPThe other alternative is a combined method, treating domestic wastewater and leachate together. The treatment is biological in nature using a SBR with phases fill, react, settle and decant. The treating system consisted of aerating the SBR, composed of sludge, domestic wastewater and leachate, for a period of 24 hours. The volume of leachate was gradually increased until no further treatment was observed. The main parameters were monitored, pose emphasis on the nitrification process. The values were recorded and analyzed.Experimental Procedure little reactors of capacity 5 L each were considered with an MLSS concentration of 1500 mg/l.The first SBR was made up of 100% DWW and sludge only, the second one 95% DWW, 5% leachate and sludge, the third one 90% DWW, 10% leachate and sludge and so on. An example is being shown below.The dissolved oxygen concentration was kept greater than 2 mg/l by the use of air diffusers which also provided the mixing within the reactor.Immediately after the setting out of the reactor, a grab sample was collected and was tested. These values were set as baseline.After 24 hours of aeration, another sample was collected from the reactor and tests were performed.