Quality and Quantity of Leachate in Aerobic Pilot-Scale Landfills

In this study, two pilot-scale aerobic landfill reactors with (A1) and without (A2) leachate recirculation are used to obtain detailed information on the quantity and quality of leachate in aerobic landfills. The observed parameters of leachate quality are pH, chloride (Cl⁻), chemical oxygen demand (COD), biological oxygen demand (BOD), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH₃-N), and nitrate (NO₃^–-N). pH values of the leachate increased to 7 after 50 days in reactor A1 and after 70 days in reactor A2. Cl⁻ concentrations increased rapidly to 6100 (A1) and 6900 (A2) mg/L after 80 days, from initial values of 3000 and 2800 mg/L, respectively. COD and BOD values decreased rapidly in the A1 landfill reactor, indicating the rapid oxidation of organic matter. The BOD/COD ratio indicates that leachate recirculation slightly increases the degradation of solid waste in aerobic landfills. NH₃-N concentrations decreased as a result of the nitrification process. Denitrification occurred in parts of the reactors as a result of intermittent aeration; this process causes a decrease in NO₃⁻ concentrations. There is a marked difference between the A1 and A2 reactors in terms of leachate quantity. Recirculated leachate made up 53.3% of the leachate generated from the A1 reactor during the experiment, while leachate quantity decreased by 47.3% with recirculation when compared with the aerobic dry landfill reactor.     

Biological nutrient removal from pre-treated landfill leachate in a sequencing batch reactor

Biological treatment of landfill leachate usually results in low nutrient removals because of high chemical oxygen demand (COD), high ammonium-N content and the presence of toxic compounds such as heavy metals. Landfill leachate with high COD content was pre-treated by coagulation-flocculation with lime followed by air stripping of ammonia at pH=12. Nutrient removal from pre-treated leachate was carried out using a lab-scale sequencing batch reactor (SBR). Three different operations consisting of different numbers of steps were tested and their performances were compared. These operations were the three-step anaerobic (An)/anoxic (Ax)/oxic (Ox); the four-step (An/Ox/Ax/Ox), and the five-step (An/Ax/Ox/Ax/Ox) operations with total residence time of seven hours each. Experiments were carried out using three consecutive operations with a total cycle time of 21 h at a constant sludge age of 10 days. The lowest effluent nutrient levels were realized by using the five-step operation which resulted in effluent COD, NH4-N and PO4-P contents of 1,400, 107 and 65 mg l(-1), respectively, at the end of 21 h. Addition of domestic wastewater (1/1, v/v) and powdered activated carbon (PAC, 1 g l(-1)) to the pre-treated leachate improved nutrient removals in the five-step SBR operation, resulting in 75% COD, 44% NH4-N and 44% PO4-P removals after 21 hours of operation.     

污泥接种量对好氧污泥颗粒化的影响研究

考察了污泥接种体积分别为25％、50％和75％的反应器有效容积情况下的污泥颗粒化特征。结果发现，25％体积的污泥接种量利于颗粒污泥的形成和成长，其颗粒化程度高、平均粒径大且粒径分布范围广，而50％和75％体积的污泥接种量只能形成少量细小的颗粒污泥。分析认为，悬浮分散污泥是颗粒化的一个较大障碍，较少的接种量能够提供较大的自由沉淀空间，使污泥能够实现重力分层，进而排除与颗粒污泥竞争底物的悬浮不沉降污泥，从而利于颗粒化。污泥颗粒化的直接影响因素不是沉淀时间而是自由沉淀空间。沉淀时间的缩短使自由沉淀空间增加，从而影响了污泥颗粒化进程。     

SBR中好氧颗粒污泥的培养

采用竖式SBR作为反应器，利用城市污水处理厂剩余污泥作为接种污泥，通过不间断运行培养出好氧颗粒污泥。实验结果表明，采用非限量曝气模式好氧颗粒污泥降解模拟污水的效果较好，其COD去除率可达98％以上。曝气量对好氧颗粒污泥的形成和稳定具有重要影响，当气速为26．5m／h时，好氧颗粒污泥的性状和处理有机废水效果最佳。同时好氧颗粒污泥对pH值的变化不明显，当pH为5—8范围内，其COD去除率都可达到85％以上。但是未经驯化的好氧颗粒污泥对对硝基苯酚和对氯苯酚两种芳香类有机物较敏感，而对硝基苯酚对其毒性更大。当对硝基苯酚和。对氯苯酚浓度为10mg／L时，其COD去除率仅为42．5％和52％。     

酸性条件下厌氧颗粒污泥活性抑制与恢复试验研究

取食品生产废水处理中试工程运行中现有的厌氧颗粒污泥进行活性抑制与恢复试验。通过慢性致毒与急性致毒作用的对比,分析酸性条件对颗粒污泥的抑制作用,研究颗粒污泥的耐酸性,并考察污泥活性恢复方法。结果表明:当进水pH=6.5,颗粒污泥活性受到轻微抑制,不影响系统的稳定运行;当pH值下降至4.5时,COD去除率和产甲烷量均趋于零。同时使用调节进水pH值、降低进水有机负荷、提高进水碱度以及调整水力停留时间等4种方法能有效恢复污泥活性,活性达到抑制前的80%左右。     

Biological treatment of anaerobically digested palm oil mill effluent (POME) using a Lab-Scale Sequencing Batch Reactor (SBR)

The production of highly polluting palm oil mill effluent (POME) has resulted in serious environmental hazards. While anaerobic digestion is widely accepted as an effective method for the treatment of POME, anaerobic treatment of POME alone has difficulty meeting discharge limits due to the high organic strength of POME. Hence, subsequent post-treatment following aerobic treatment is vital to meet the discharge limits. The objective of the present study is to investigate the aerobic treatment of anaerobically digested POME by using a sequencing batch reactor (SBR). The SBR performance was assessed by measuring Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) removal as well as Sludge Volume Index (SVI). The operating pH and dissolved oxygen concentrations were found to be 8.25–9.14 and 1.5–6.4 mg/L, respectively, throughout the experiment. The experimental results demonstrate that MLVSS, OLR and sludge loading rate (SLR) play a significant role in the organic removal efficiency of SBR systems and therefore, further investigation on these parameters was conducted to attain optimum SBR performance. Maximum COD (95–96%), BOD (97–98%) and TSS (98–99%) removal efficiencies were achieved at optimum OLR, SLR and MLVSS concentration ranges of 1.8–4.2 kg COD/m³ day, 2.5–4.6 kg TSS/m³ day and 22,000–25,000 mg/L, respectively. The effluent quality remained stable and complied with the discharge limit. At the same time, the sludge showed good settling properties with average SVI of 65. It is envisaged that the SBR process could complement the anaerobic treatment to produce final treated effluent which meets the discharge limit.     

Biological treatment of tannery wastewater in the presence of chromium

Experiments were carried out to determine the feasibility of treating tannery wastewater containing chromium, an inhibiting compound, with sequencing batch reactors (SBR). The maximum chromium concentration tolerated by microorganisms was determined through aerobic and anoxic batch experiments, and the biomass inhibition process was analyzed in a lab scale reactor at increasing chromium concentrations. The results obtained, in batch experiments and in the SBR reactor, have demonstrated that chromium addition had less influence on the denitrification bacteria than on the nitrification bacteria. In addition, it was observed that nitrification and denitrification rates, at the same chromium concentration, were higher in the SBR reactor than in batch experiments with unacclimated biomass. Experimental results confirm that sequencing batch reactors are able to produce a more resistant biomass, which acclimates quickly to inhibiting conditions. A large amount of chromium was found in the sludge from the reactor, while the effluent was devoid of the inhibiting metal.     

好氧颗粒污泥同时脱氮除磷技术研究

采用序批式活性污泥法(SBR)处理新疆油田公司准东石油基地污水,作为生物膜的一种特殊形式,介绍了该工艺的优点,在适宜的运行条件下进行实验。讨论了好氧颗粒污泥脱氮以及除磷的过程,分析了该工艺对氮、磷的去除率及好氧颗粒污泥在好氧、缺氧条件下的吸磷情况,当进水氨氮、磷和乙酸碳浓度分别为38.2 mg/L、27.7 mg/L和134.6 mg/L,MLSS和MLVSS分别为7.0 mg/L、6.4 mg/L时,氨氮、总无机氮、磷、乙酸碳的平均去除率分别达到98.8%、90.2%、98.9%、97.2%.     

好氧颗粒污泥技术

好氧颗粒污泥技术是近几年来发展起来的废水处理技术，它能有效地去除废水中的有机物、COD、氨氮、难降解的有毒有机物、硫磷、重金属离子等。本文根据国内外对其的最新研究成果对好氧颗粒污泥的特性、形成的主要影响因素以及除污功能进行了阐述。     

Studies on the toxic effects of pentachlorophenol on the biological activity of anaerobic granular sludge

In order to explore the pathway of the anaerobic biotreatment of the wastewater containing pentachlorophenol (PCP) and ensure the normal operation of Upflow Anaerobic Sludge Blanket (UASB) reactor, the anaerobic sludge under different acclimation conditions were selected to seed and start up UASB reactors. Anaerobic toxicity assays were employed to study the biological activity, the tolerance and the capacity to degrade PCP of different anaerobic granular sludge from UASB reactors. Results showed that the anaerobic granular sludge acclimated to chlorophenols (CPs) could degrade PCP more quickly (up to 9.50mg-PCPg(-1)TVSd(-1)). And the anaerobic granular sludge without acclimation to CPs had only a little activity of degrading PCP (less than 0.07mg-PCPg(-1)TVSd(-1)). Different PCP concentrations (2, 4, 6, 8mgL(-1)) had different inhibition effects on glucose utilization, volatile fatted acidity (VFA)-degrading and methanogens activity of PCP degradation anaerobic granular sludge, and the biological activity declined with the increase in PCP concentration. The methanogens activity suffered inhibition from PCP more easily. The different acclimation patterns of seeded sludge had distinctly different effects on biological activity of the degradation of PCP of anaerobic granular sludge from UASB reactors. The biological activity of the anaerobic granular sludge acclimated to PCP only was also inhibited. This inhibition was weak compared to that of anaerobic granular sludge acclimated to CPs, further, the activity could recover more quickly in this case. In the same reactor, the anaerobic granular sludge from the mid and base layers showed higher tolerance to PCP than that from super layer or if the sludge is unacclimated to CPs, and the corresponding recovery time of the biological activity in the mid and base layers were short. Acetate-utilizing methanogens and syntrophic propinate degraders were sensitive to PCP, compared to syntrophic butyrate degraders.     

Nitrogen and phosphorus removal from domestic strength synthetic wastewater using an alternating pumped flow sequencing batch biofilm reactor

Nutrient removal from domestic strength synthetic wastewater by an alternating pumped flow sequencing batch biofilm reactor (APFSBBR) was investigated in this laboratory study. The APFSBBR comprised two reactor tanks (Reactors 1 and 2) with two identical biofilm modules of vertical tubular plastic media with a high specific surface area, one in each tank. The APFSBBR was operated in cycles of four phases: fill, anaerobic, aerobic, and draw. During the fill phase, Reactor 1 was half-filled with domestic strength synthetic wastewater. During the subsequent anaerobic phase, most of the phosphorus release took place from the submerged biofilm in this reactor. In the aerobic phase, the wastewater was circulated by pumps between Reactors 1 and 2, resulting in denitrification at the start of the aerobic phase due to low oxygen concentrations, followed by nitrification and luxury uptake of phosphorus when oxygen concentrations increased. During the draw phase, Reactor 2 was half-emptied of the treated water. At the chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) loading rates on the total biofilm area of 3.20 g COD, 0.33 g TN, and 0.06 g TP m(-2) d(-1), the removal efficiencies were 97, 85, and 92% for COD, TN, and TP, respectively.     

The effect of landfill leachate composition on organics and nitrogen removal in an activated sludge system with bentonite additive

A pre-denitrification activated sludge system (AS) without internal recycle was used in lab-scale studies of landfill leachate treatment. A bentonite supplement at a ratio of 1:4 (mineral : biomass) was used to ensure high sludge settling levels and to serve as a micro-organisms carrier. The system was operated within different parameters such as hydraulic retention time (HRT), ammonia loading rate (ALR) or external recycle ratio, which was adapted to treat varying leachate concentrations of COD and ammonia, ranging from 1020 to 2680 mgO(2)l(-1) and 400-890 mgNH(4)-Nl(-1) respectively. The nitrification was complete and ammonia oxidation reached 99%; this was obtained while the ALR did not exceed 0.09 g NH(4)(+)-Ng(-1)MLVSS d(-1) and HRT was not lower than 1 day (in the aeration reactor). The performance of denitrification was successfully improved by controlling the external recycle rate, when the BOD(5)/N ratio in the raw leachate was 4.1. Consequently, N-removal of up to 80% was achieved. A 10-fold decrease in the denitrification rate was obtained at a BOD(5)/N ratio of 0.5. The efficiency of COD removal varied significantly from 36% to 84%. The positive effect of bentonite addition was determined and is discussed based on preliminary studies. The experiments were carried out in fill-and-draw activated sludge with bentonite; the biomass ratio was 1:2. The activated sludge with bentonite was fed with a synthetic high ammonia and organic-free medium.     

Anaerobic whey treatment by a stirred sequencing batch reactor (ASBR): effects of organic loading and supplemented alkalinity

An assessment was made of cheese whey treatment in a mechanically stirred anaerobic sequencing batch reactor (ASBR) containing granular biomass. The effect of increasing organic load and decreasing influent alkalinity supplementation (as sodium bicarbonate) was analyzed. The reactor operated on 8-h cycles with influent COD concentrations of 500, 1000, 2000 and 4000 mg/L, corresponding to volumetric organic loads of 0.6 to 4.8 mgCOD/L.d. Organic COD removal efficiencies were always above 90% for filtered samples. These results were obtained with an optimized alkalinity supplementation of 50% (ratio between mass of NaHCO3 added and mass of influent mgNaHCO3/mgCOD) in the assays with 500 and 1000 mgCOD/L and of 25% in the assays with 2000 and 4000 mgCOD/L. Initial alkalinity supplementation was equal to the mass of influent COD (100%). The system showed formation of viscous polymer-like substances. These were probably of microbiological origin occurring mainly at influent CODs of 2000 and 4000 mg/L and caused some biomass flotation. This could, however be controlled to enable efficient and stable reactor operation.     

SBR法处理啤酒废水DO对丝状菌污泥膨胀的影响

溶解氧(DO)浓度是影响丝状菌污泥膨胀最重要的因素之一。选用具有代表性的啤酒废水为处理对象,研究了SBR工艺中DO浓度对丝状菌污泥膨胀的影响。结果表明:高DO浓度(4～6.5mg/L)不会导致丝状菌污泥膨胀;低DO浓度能引起丝状菌污泥膨胀,当DO浓度降低至0.4mg/L时,SVI升高到210mL/g,会导致污泥膨胀发生。低DO浓度下污泥膨胀发生后,在较高的DO浓度条件下运行一定的周期数后,污泥膨胀能得到有效控制,使污泥沉降性能恢复到正常水平。     

UAFSB反应器处理畜禽废水的快速启动

对UASB反应器进行改型，得到UAFSB，并结合UASB反应器快速启动的驯化方式，比较分析用畜禽废水直接启动加颗粒活性炭与未加颗粒活性炭的运行过程和结果。试验结果表明：絮状污泥接种后经过54天的驯化，进料COD浓度由800mg／L提高到5000mg／L，去除率基本稳定在90％以上，均达到预期目的；在污泥中掺入颗粒活性炭，反应器的启动时间有所缩短、抗冲击能力有所加强。     

粪渣污泥上清液和填埋场渗滤液混合处理工程分析

针对深圳市的情况,提出将粪渣污泥脱水上清液和玉龙坑垃圾填埋场渗滤液进行混合处理的工程方案。经过比较,推荐上清液和渗滤液混合废水的处理采用ＵＡＳＢ和好氧生物处理工艺,脱水粪渣和剩余污泥的处理则采用高温好氧堆肥的方案,使排放出水达到排放标准的要求下,做到了污泥的资源化利用,工程和运行管理方面也是可行的。     

溶解氧对好氧颗粒污泥影响的研究进展

好氧颗粒污泥技术是一种新颖废水处理技术。溶解氧(DO)是好氧颗粒污泥形成和稳定运行的一个重要参数。好氧颗粒污泥需要的曝气量大,能耗高。高曝气量带来的高DO浓度不利于氨氮通过SND去除。当DO扩散在颗粒内部受到限制时,颗粒中心形成的厌氧层不利于颗粒污泥的长期稳定运行。本文系统分析了DO浓度对好氧颗粒污泥影响的国内外研究现状,对好氧颗粒污泥中DO浓度这一重要参数的研究进行了总结。研究在低DO浓度下保持好氧颗粒污泥的稳定性有利于降低运行成本,采取合适的方法降低颗粒内部的扩散限制有利于增强颗粒的稳定性能。     

Estimation of Biogas Generation from a Uasb Reactor via Multiple Regression Model

In this study, regression analysis based an estimation model for biogas generated from an up-flow anaerobic sludge blanket (UASB) reactor treating landfill leachate is developed using several leachate parameters, such as pH, conductivity, total dissolved solids, chemical oxygen demand, alkalinity, chloride, total Kjeldahl nitrogen, ammonia, total phosphorus. These landfill leachate parameters are monitorized over a period of 1000 days at 35 ± 1°C in the UASB reactor. In order to develop the best model giving highest estimation performance, eight model equations including different input parameter combinations are analyzed. Based on the results of regression analysis, the best coefficients of the model equation are determined. As a conclusion, the developed model in this study can give accurate biogas amount prediction for the USAB reactor-based leachate treatment system.     

Treatment of Landfill Leachate Wastewater by Nanofiltration Membrane

Abstract

Nanofiltration (NF) membrane is an alternative lower energy membrane type compared to reverse osmosis membrane. NF is suitable for rejection of ions and molecules with molecular weight greater than 200 Da. In this study leachate wastewater from a sanitary landfill site in Malaysia was filtered through a NF membrane in order to determine the rejection capability of the membrane towards pollutants such as chemical oxygen demand (COD), conductivity, nitrate, ammonia-nitrogen, and heavy metals such as Pb, Cd, Cu, Zn, Fe. The NF membrane used was HL membrane, which under the atomic force microscope (AFM) imaging, showed visible discrete pores. The overall rejections of the pollutants were more than 85% except for nitrate and ammonia nitrogen. NF can be considered an alternative for advanced filtration especially within a hybrid treatment system combining biological–physical treatment and membrane filtration.     

SBR系统中pH与MLSS对同步硝化反硝化的影响

本文研究了SBR系统中pH值、MISS的变化对同步硝化反硝化的影响。结果表明：在进水水质和反应条件相同时，将pH值控制在8．5，出水水质最好，COD去除率达到90．0％，总氮去除率达到99．4％；在进水水质和反应条件相同，反应器中MLSS为520mg／L时，出水水质最好，COD去除率达到85馏％，总氮去除率达到99．1％。