Removal of organics from leachates by anaerobic filter

A laboratory-scale study was conducted on two anaerobic filters at several loading rates and four hydraulic detention times. Feed substrates were landfill leachates taken from a recently opened landfill (Keele Valley) and from an older site (Brock North) which had been closed for about 8 years. The strong raw leachate from the new landfill had a COD of 14,000 mg l⁻¹, a BOD/COD ratio of 0.7 and a COD/P value of 17,900. The partially stabilized leachate from the older landfill had a COD of only 3750 mg l⁻¹, a BOD/COD ratio of 0.3 and a COD/P value of 30,640.Results from the treatment of the two leachates were compared with those from a previous study of a “mature” landfill (Beare Road). It was demonstrated that the anaerobic filter could reduce the COD of leachate from landfills of different ages by 90%, at loading rates of 1.26–1.45 kg COD m⁻³ d⁻¹. Total biogas production ranged between 400 and 500 l gas kg⁻¹ COD destroyed and methane content between 75 and 85%. No phosphorus addition was required over the loading range studied.     

Removal and transformation of recalcitrant organic matter from stabilized saline landfill leachates by coagulation-ozonation coupling processes

The Bordo Poniente sanitary landfill in Mexico City currently receives 11,500 ton/day of solid wastes. The landfill has been in operation since 1985, in what was formerly Texcoco Lake, now a dried-up lakebed. The physico-chemical characteristics of the leachate generated by this particular landfill are altered by the incorporation of freatic saline water present in the area. This paper reports the results from a study evaluating coagulation and ozonation as alternative processes for removing and transforming recalcitrant organic matter from stabilized saline landfill leachate. Coagulation with ferric sulfate was found to remove up to 67% of COD and 96% of leachate color. The remaining 33% COD was removed with ozone. Recalcitrant organic matter removal by ozonation is limited by the reaction kinetic due mainly to ozone's low reactivity with the organic compounds present in the leachates (amines, amides, alcohols, aliphatic compounds, and carboxylic acids). However, ozone contributes greatly to changing the recalcitrant characteristics of organic matter. Leachate biodegradability was found to be significantly enhanced through ozonation: BOD(5) values reach 265%, and the BOD(5)/COD ratio increases from 0.003 to 0.015. Infrared analysis of ozonated leachates shows that the main by-products of recalcitrant organic matter ozonation are an increase in the hydroxyl and carboxylic groups, and the presence of aldehydes groups.     

Removal of non-biodegradable organic matter from landfill leachates by adsorption

Leachates produced at the La Zoreda landfill in Asturias, Spain, were recirculated through a simulated landfill pilot plant. Prior to recirculation, three loads of different amounts of Municipal Solid Waste (MSW) were added to the plant, forming in this way consecutive layers. When anaerobic digestion was almost completed, the leachates from the landfill were recirculated. After recirculation, a new load of MSW was added and two new recirculations were carried out. The organic load of the three landfill leachates recirculated through the anaerobic pilot plant decreased from initial values of 5108, 3782 and 2560 mg/l to values of between 1500 and 1600 mg/l. Despite achieving reductions in the organic load of the leachate, a residual organic load still remained that was composed of non-biodegradable organic constituents such as humic substances. Similar values of the chemical oxygen demand (COD) were obtained when the landfill leachate was treated by a pressurised anoxic-aerobic process followed by ultrafiltration. After recirculation through the pilot plant, physico-chemical treatment was carried out to reduce the COD of the leachate. The pH of the leachate was decreased to a value of 1.5 to precipitate the humic fraction, obtaining a reduction in COD of about 13.5%. The supernatant liquid was treated with activated carbon and different resins, XAD-8, XAD-4 and IR-120. Activated carbon presented the highest adsorption capacities, obtaining COD values for the treated leachate in the order of 200mg/l. Similar results were obtained when treating with activated carbon, the leachate from the biological treatment plant at the La Zoreda landfill; in this case without decreasing the pH.     

UASB/吹脱塔/SBR/纳滤工艺处理生活垃圾渗滤液

采用UASB/吹脱塔/SBR/纳滤工艺处理垃圾渗滤液,处理规模为800m3/d,垃圾渗滤液COD为8 000～12 000mg/L、BOD5为3000～5 500mg/L、SS为500～800mg/L、NH3-N为1 000～2 000 mg/L,出水COD≤l00mg/L、BOD5≤30 mg/L、SS≤30 mg/L、NH3-N≤25 mg/L,达到国家新建<生活垃圾填埋场污染控制标准>(GB 16889-2008).运行结果表明,该工艺运行稳定,处理效果好.     

TiO2、Cu2O和氧化石墨烯复合氧化垃圾渗滤液效能

针对垃圾渗滤液中成分复杂的污染物,在自然光照条件下,使用TiO₂/氧化石墨烯、Cu₂O/氧化石墨烯和TiO₂/Cu₂O三种复合催化剂分别对垃圾渗滤液原液进行催化氧化。结果表明,3种复合催化剂中,TiO₂/氧化石墨烯复合催化剂对有机物的去除效果最好,当催化剂与渗滤液COD的质量比为0.7时为该催化剂的最佳投加量,最佳反应时间为2 h。在最佳试验条件下,对垃圾渗滤液原液进行催化氧化后,对COD的去除率达到92.57%,此时渗滤液出水COD为964.79mg/L,出水NH4⁺-N为2015.84 mg/L,BOD₅/COD值达到0.83。     

投粉末活性炭SBR处理垃圾渗滤液

结合小型垃圾填埋场渗滤液中有机物浓度较低的特点及简化工艺的要求,以南京市某垃圾填埋场渗滤液为试验对象,经氨吹脱后采用投粉末活性炭SBR/混凝沉淀工艺进行处理,探讨了粉末活性炭投量、泥龄等参数对处理效果的影响.结果表明,对COD、BOD5、NH3-N的总去除率分别为88.4%、93.4%、76.9%,出水水质达到了<生活垃圾填埋场污染控制标准>(GB16889-1997)的Ⅱ级标准.     

Leachate Collection, Treatment and Disposal

As landfills become larger, the enormous quantities of putrescible wastes which they contain have increased the potential to generate highly polluting leachates as they decompose anaerobically over many years. If severe environmental impacts are to be avoided, operators must control these liquors: many landfill proposals stand or fall on the ability of the operator to demonstrate that leachate can be collected, managed and disposed of in an environmentally acceptable manner. During the early years of tipping in containment cells, high BOD and COD values (to 50 000 mg/l or more) are measured, with very high ammonia concentrations (to more than 1000 mg/l as N) persisting for many years.
The authors have been involved with the full-scale on-site treatment of leachates to high standards in automated aerated lagoon plants since the early 1980s. The first plant was constructed in 1982, and a further seven have since been built at landfills throughout the UK, with many more at various stages of design and construction – both in the UK and overseas.
This paper describes detailed operational experiences from several of these landfill sites, with particular emphasis on the reduction of ammonia concentrations to low values. The use of reed-bed treatment schemes as effluent polishing facilities is also discussed.     

空化水射流处理垃圾渗滤液实验研究

以重庆某垃圾填埋场的渗滤液为研究对象,采用空化水射流空化降解垃圾渗滤液中复杂有机物,通过实验研究了泵压、围压、pH值和空化时间对空化处理垃圾渗滤液的影响规律,得出了空化水射流能降解有机物,从而显著提高渗滤液的可生化性的结论,同时确定了最佳空化条件是围压0.6 MPa,pH值9.0,空化处理时间90 min,泵压10 MPa。在最佳条件下空化处理垃圾渗滤液,COD和BOD5分别上升了124.8%和293.3%,BOD5/COD也提高了52.44%,色度降低,SS提高了191.5%,为后续处理创造有利条件。     

Biological nitrogen removal from municipal landfill leachate: low-cost nitrification in biofilters and laboratory scale in-situ denitrification

The slow leaching of nitrogen from solid waste in landfills, resulting in high concentrations of ammonia in the landfill leachate, may last for several decades. The removal of nitrogen from leachate is desirable as nitrogen can trigger eutrophication in lakes and rivers. In the present study, a low-cost nitrification-denitrification process was developed to reduce nitrogen load especially in leachates from small landfills. Nitrification was studied in laboratory and on-site pilot aerobic biofilters with waste materials as filter media (crushed brick in upflow filters and bulking agent of compost in a downflow filter) while denitrification was studied in a laboratory anoxic/anaerobic column filled with landfill waste. In the laboratory nitrification filters, start-up of nitrification took less than 3 weeks and over 90% nitrification of leachate (NH4-N between 60 and 170mg N l(-1), COD between 230 and 1,300 mg l(-1)) was obtained with loading rates between 100 and 130 mgNH4-N l(-1) d at 25 degrees C. In an on-site pilot study a level of nitrification of leachate (NH4-N between 160 and 270 mg N l(-1), COD between 1,300 and 1,600 mg l(-1)) above 90% was achieved in a crushed brick biofilter with a loading rate of 50mg NH4-N l(-1) d even at temperatures as low as 5-10 degrees C. Ammonium concentrations in all biofilter effluents were usually below the detection limit. In the denitrification column. denitrification started within 2 weeks and total oxidised nitrogen in nitrified leachate (TON between 50 and 150mg N l(-1)) usually declined below the detection limit at 25 degrees C, whereas some ammonium, probably originating from the landfill waste used in the column, was detected in the effluent. No adverse effect was observed on the methanation of waste in the denitrification column with a loading rate of 3.8 g TON-N/t-TS(waste) d. In conclusion, nitrification in a low-cost biofilter followed by denitrification in a landfill body appears applicable for the removal of nitrogen in landfill leachate in colder climates.     

Treatment of landfill leachate by combined aged-refuse bioreactor and electro-oxidation

Two-stage aged-refuse bioreactor (ARB) was applied to treat landfill leachate in Shanghai Waste Laogang Disposal Plant. The removal efficiencies of chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), total nitrogen (TN) and ammonia nitrogen (NH(3)-N) of landfill leachate treated by the two-stage bioreactor system were 98.5%, 99.9%, 98.0%, 64.2% and 99.9%, respectively. The COD and BOD in the second stage effluent were 239 and 7 mg l(-1), respectively. Thus three types of electrolysis were employed to further treat the second effluent, undivided electrolysis (UDE), divided electrolysis (DE) with Ti/PbO(2) cathode and DE with gas diffusion cathode. All electrolysis processes possessed good color removal effect, while the DE with gas diffusion cathode had the best TOC removal effect. The optimum electrolysis time of leachate was 30 min. The TOC removal efficiencies were 51.4% and 39.7% in anolyte and catholyte, respectively, after 30 min electrolysis at 5 V. In addition, the DE with gas diffusion cathode showed the least energy consumption of 9.8 k Whm(-3) at 30 min. The organic pollutants in the leachate were analyzed through a gas chromatography coupled with mass spectrometry (GC-MS) system. Through the two-stage ARB, the species and concentrations of organic pollutants in landfill leachate reduced greatly. Several chlorinated organic compounds were detected in the effluent after the UDE and the anolyte of the DE. In addition, the concentration of absorbable organic halogens (AOX) increased greatly during the electrolysis. Hence, careful consideration should be given in the application of electro-oxidation into the treatment of chloride-containing wastewater.     

Dissolved organic matter (DOM) in recycled leachate of bioreactor landfill

Landfill leachate needs sufficient treatment before safe disposal. Bioreactor landfill technology could effectively degrade the organic matters in recirculated leachate, hence leaving a leachate stream of low biodegradability. This study characterized the dissolved organic matter (DOM) in the leachate from simulated bioreactor landfill columns with or without presence of trace oxygen. The removal efficiencies of this DOM using coagulation-sedimentation or electrolysis processes were demonstrated. Recirculated leachates were sampled from the simulated landfill columns applying conventional mode, intermittent-aeration mode, and natural aeration mode, whose DOM was fractionated into humic acids (HA), fulvic acids (FA) and hydrophilic fractions (HyI) by the XAD-8 resin combined with the cation exchange resin method. The recirculated leachate had low BOD/COD ratio, high humic substances contents, and high aromatic content. Their HA fraction comprised mainly large molecules (>10 k Da), while the FA and HyI were composed of smaller molecules (<50 k and <4 k Da, respectively). With the presence of oxygen, the TOC contents and the contents of HA, FA and HyI in leachate reduced, with FA and HyI fractions of molecular weight (MW) lower than 4 k Da more readily degraded. The organic matters left in leachates from intermittent-aeration mode and natural aeration mode were of low biodegradability. It was tested in the following sections the effects of coagulation-sedimentation process and of electrolysis process on the removal of residual DOM in recirculated leachate. Coagulation-sedimentation tests revealed that poly ferric sulphate (PFS) could remove more COD (58.1%) from leachate than polyaluminum chloride (PACl) (22.9%), particularly on the HA fraction with MW>10 k Da. Coagulation-sedimentation could not remove most of HyI in leachate. Furthermore, the corresponding BOD/COD ratio was not improved through coagulation. Electrolysis test could also effectively removed HA of MW>10 k Da. However, the biodegradability of treated effluent considerably was improved. The electrolysis could decompose high MW substances and increase biodegradability of recirculated leachate from bioreactor landfill.     

Combined γ-ray irradiation-activated sludge treatment of humic acid solution from landfill leachate

Humic acid, which is a typical microbially refractory organic substance, was extracted from a landfill leachate. The humic acid solution (COD = 367 mg 1⁻¹; TOC = 293 mg 1⁻¹; BOD = 27 mg 1⁻¹) was applied to a batch scale activated sludge treatment after the modification of its biodegradability by γ-ray irradiation. The BOD increased to 64 mg 1⁻¹ by irradiation of 15 kGy (1.5 Mrad), while the COD and TOC decreased to 231 and 230 mg 1⁻¹, respectively. When the irradiated sample was treated with an activated sludge, the BOD decreased rapidly in 2–3 h to about 15 mg 1⁻¹ which was a similar value as the unirradiated sample was treated. The elimination efficiency of TOC by the sludge treatment was approximately equal to that obtained by irradiation of 15 kGy. These facts suggest a utility of applying microbial processes after radiation treatment of microbially refractory wastewaters.     

Water quality and pollution loading of a river segment affected by landfill leachate and domestic waste

The Marikina River in the Philippines has been polluted by Payatas landfill leachate, and domestic and agricultural waste. This study monitored the water quality at five stations on the river and two stations on two creeks that discharge to the river to determine the effects of Payatas landfill and to estimate pollution loading. The dissolved oxygen (DO), chemical oxygen demand (COD) and other water quality parameters were compared with the Philippines Standards for river water classification. It was found that Payatas leachate has a significant influence on the DO and COD levels as well as other water quality parameters. Per capita pollution loading for Quezon City was found to be lower than for Europe and Japan. The effect of leachate is more significant during the dry season. It is recommended that a leachate collection system be established to prevent leachate form entering Payatas creek, and that the Patayas landfill be replaced with a modern landfill site, conforming to current best practice at another location.

List of Abbreviation: BOD= Biological Oxygen Demand COD = Chemical Oxygen Demand DO = Dissolved Oxygen EC = Electrical Conductivity M1, M2, M3, M4, M5 = monitoring stations TDS = Total Dissolved Solids TSS = Total Suspended Solids     

The treatment of leachates from domestic wastes in landfills—I: Aerobic biological treatment of a medium-strength leachate

A medium-strength leachate from domestic solid wastes in a landfill (COD 5000 mg l⁻¹, BOD 3000 mg l⁻¹ was treated using aerobic biological processes in continuous-flow, laboratory-scale reactors at low temperatures. Each unit was completely mixed, and mixed liquor was wasted such that solids retention time (SRT) was equal to the hydraulic retention period.At 10 C with addition of phosphate (COD:P less than 100:1) SRT values of 10 days were required to obtained well-clarified effluents, and high removal of BOD (>;98%) and COD (>;92%). Reduction of temperature to 5°C resulted in adverse effects on settling of sludges from units with SRT values of less than 10 days, but in other units good removal of organic materials could still be obtained. These units operated successfully with concentrations of mixed liquor volatile suspended solids (MLVSS) of 1450 mg l⁻¹, equivalent to a ratio of F/M of 0.21 kg BOD kg⁻¹ MLVSS day⁻¹ or less. Removal of ammoniacal nitrogen which took place (influent concentration 80 mg l⁻¹ as N) resulted from incorporation in biomass, and at SRT values of 10 days no nitrification took place at 5 or 10 C. Higher concentrations of ammonia in influent leachates resulted in ammonia in effluents when the ratio of BOD:N was less than about 100:3.6. Increasing the SRT of units to 20 days resulted in erratic conversion to nitrite, but reduced pH-values and possible simultaneous denitrification caused floating sludges and poorly-clarified effluents. Removal of ammonia is identified as a major problem when treating leachates, and further research is recommended.     

Optimization of the landfill leachate treatment by the Fenton process

The Fenton process was used with the objective of improving the biodegradability of the leachate pretreated biologically up to a value compatible with a subsequent biological treatment. The optimum reaction and settlement pH was 3, both for the organic matter removal and for the improvement of the biodegradability. The chemical oxygen demand (COD) removal increased at increasing Fe²⁺ dosages, from 75.6% for 300 mg/L to 89.0% for 1400 mg/L. The most significant enhancement (84.8%) was obtained with 800 mg Fe²⁺/L. However, the biological oxygen demand/chemical oxygen demand ratio (BOD/COD) was almost the same at all the Fe²⁺ dosages, around 0.29. Moreover, varying the H₂O₂ concentration between 600 and 3600 mg/L, COD removal percentages were between 85.9 and 89.0%. However, the BOD/COD ratio increased at increasing H₂O₂ dosage up to 3000 mg/L, from 0.12 at 600 mg/L to 0.29 at 3000 mg/L.     

Aged raw landfill leachate: membrane fractionation, O3 only and O3/H2O2 oxidation, and molecular size distribution analysis

Large molecular refractory organic compounds (i.e., humic substances) were the major chemical oxygen demand (COD) components of aged raw landfill leachate. To investigate the behaviours of the large molecular refractory organic compounds when they were subjected to oxidation with ozone only (O3 only) and ozone combined with hydrogen peroxide (O3/H2O2), the aged raw landfill leachate first was filtered with 0.8 and 0.45 microm pore size filters in series, then was sequentially fractionated with 10,000 MWCO; 5000 MWCO; and 1000 MWCO membranes, and four samples were formed: 0.45 microm-10,000 Da; 10,000-5000 Da; 5000-1000 Da; and < 1000 Da. Mass distribution profiles of COD, 5-day biochemical oxygen demand (BOD5), colour and metals in the aged raw leachate were developed through mass balance. After membrane fractionation of the aged raw leachate, the metals were fractionated with the humic substances. Each fractionated sample as well as the aged raw leachate was oxidised with O3 only and O3/H2O2. The H2O2 enhanced the reduction of COD and colour; while, the BOD5 after O3 only was always higher than that of O3/H2O2. The addition of H2O2 improved the peak reduction of large molecules, but the effects of H2O2 on the fractions of 10,000-5000 Da and 5000-1000 Da were likely insignificant, which is in accordance with the COD results. No correlation was found between the BOD5 increase and the area of new peak formed after oxidation. However, the BOD5 of each sample after oxidation with O3 only was the logarithmic function of its total peak area.     

城镇居民人均日生活污水污染物产生量测算之产污规律

选择常州市某居民楼宇开展居民生活污水污染物的源头产生量及规律研究。检测日的居民生活污水人均日排放量为216 L/(人·d),在06:30—10:30和19:00—21:30两个时段分别出现较高值,最大时排放量和日均时排放量的比值为1.92;楼宇排水口COD、BOD5、NH3-N、TN和TP日均浓度分别为549、259、45.43、79.23和7.45 mg/L,也出现了两个较高值,其中第一个高峰时段提前至凌晨,最大浓度与日均浓度的比值分别为1.63、1.56、2.15、2.01和2.03;人均日污染物产生量分别为121、59、9.5、17.0和1.6 g/(人·d),同样在06:30—10:30和19:00—21:30出现两个高峰时段,但污染物产生量的时变化更加显著,最大值和最小值的比值分别达到15.68、19.68、9.22、14.16和14.20;BOD5/COD、BOD5/NH3-N、BOD5/TN和BOD5/TP日均浓度比值分别为0.47、5.71、3.27和34.82,其中BOD5/COD比值波动不明显,最大值与最小值的比值仅为1.63,而BOD5/NH3-N、BOD5/TN和BOD5/TP的比值波动较为明显,均在08:30—20:30时段出现相对较大值。     

混凝/化学氧化/曝气生物滤池深度处理垃圾渗滤液

随着垃圾渗滤液的老龄化,常规的生化处理已经不能使出水达标排放,需要进行深度处理。采用混凝／化学氧化／曝气生物滤池联合工艺深度处理垃圾渗滤液,进水COD为700mg／L左右,出水COD〈100mg／L,去除率〉85％,排放口水质达到《生活垃圾填埋污染控制标准》（GB16889--1997）一级标准。     

水解/好氧MBR组合工艺处理非稳定期垃圾渗滤液

以非稳定期垃圾填埋场的渗滤液为对象，研究了水解／好氧MBR组合工艺对COD和氮污染物的去除效果和规律。在HRT为1～4．7d、回流比为300％以及进水的COD为400～7600mg／L、氨氮为247．1～1643．8mg／L、TN为258．7～1743mg／L的条件下，对COD、氨氮和TN的去除率分别为80％～88％、〉99％和70％～82．2％，说明该组合工艺对渗滤液中的COD和氮污染物具有较好的去除效果。     

生活垃圾渗滤液处理中试研究

开发了一种适于处理高浓度垃圾渗滤液的工艺。试验表明，采用复合厌氧反应器和A／O淹没式生物膜曝气池及碱化吹脱塔技术可以有效地去除渗滤兴中的COD、BOD和氨氮。该成果已用于深圳下垃圾卫生填埋场的设计。