等离子体技术用于垃圾渗滤液预处理

采用高压脉冲放电产生非平衡等离子体对垃圾渗滤液进行预处理，通过改变放电次数、渗滤液的pH值以及起始COD、BOD5、NH3-N浓度来考察预处理的效果。试验表明该技术是可行的，预处理后很多难降解有机物变成了可降解物质，渗滤液的COD与BOD，值升高(放电一次后COD与BOD5升高幅度最大可达到30％以上)。同时大部分的氨氮可被去除，不调节pH值时放电一次的氨氮去除率平均在30％～40％，调节pH值后去除率可达到60％以上。     

大型准好氧填埋场渗滤液水质特性的研究

为进一步验证准好氧填埋技术的实用性,在成都市长安垃圾填埋场内进行了三个规模均为10 m×10 m×5 m的准好氧填埋单元试验研究,并分别对渗滤液的pH值、VFA、COD、BOD5和NH4+-N进行了分析.结果表明:对渗滤液中COD、BOD5的降解效果均较好,在分别经过742、704、697 d后,三个单元对COD的去除率分别达到了94.0%、98.0%和96.9%,对BOD5的去除率分别达到了99.4%、99.7%和99.6%;由于受到渗滤液收集管管径较小的限制,对NH4+-N的降解效果较差,因此需要根据准好氧填埋场的规模来调整渗滤液收集管的管径.     

零价铁活化过硫酸盐处理渗滤液生化尾水

采用零价铁催化过硫酸盐处理垃圾渗滤液生化尾水,考察了pH值、过硫酸盐和零价铁的投加量、反应时间等因素对处理效果的影响。结果表明,该方法能有效去除渗滤液生化尾水中的污染物,在废水pH值为3、零价铁投加量为0.5 g/L、过硫酸钠投加量为2.5 g/L的最佳条件下,反应12 h后对COD和色度的去除率分别高达71%和90%。对比不同过硫酸盐氧化体系的试验结果,发现过硫酸钠对垃圾渗滤液的处理效果优于过硫酸钾。红外光谱分析结果表明,水样中的大分子有机物被硫酸根自由基氧化成了小分子有机物。     

微波强化Fenton氧化法处理垃圾渗滤液试验研究

针对垃圾渗滤液中难降解有机物的处理效能低、成本高的问题,探讨了微波强化Fenton氧化法处理垃圾渗滤液的效能,考察了微波加热时间、微波功率、催化荆投量、pH、Fenton试剂投量等对处理效能的影响,并通过正交试验考察了各因素的综合影响.试验结果表明:在pH值为2.5、H2O2投量为6.25 mL/L、FeSO4·7H2O投量为3.972 g/L、反应时间为5 min、活性炭投量为5 g/L的条件下,可使渗滤液COD由1 652 mg/L降至205 ms/L(去除率为87.5%),达到垃圾渗滤液的二级排放标准.各因素对处理效果的影响程度依次为:Fenton试剂投量>pH>催化剂投量>反应时间.与Fenton氧化法相比,微波强化Fenton氧化法可节省50%的投药量,降低了处理成本.     

动态厌氧/两级AO型MBR/RO处理垃圾渗滤液

针对含高浓度有机物和氨氮的城市垃圾渗滤液,采用UASB/一级AO/二级AO/超滤/反渗滤(RO)工艺处理垃圾渗滤液。原水COD约10 700 mg/L,BOD5约3 650 mg/L,NH3-N约1 150 mg/L,10个月的调试与运行结果表明,该工艺对渗滤液的COD、BOD5、NH3-N的去除率分别为(89%～93.5%)、(99.3%～99.5%)、(99%～99.2%),出水COD≤100 mg/L、BOD5≤30 mg/L,NH3-N≤25 mg/L、TN≤40 mg/L,达到《生活垃圾填埋场污染控制标准》(GB 16889—2008)中的表2标准。     

响应面法优化电解芬顿协同法深度处理老龄垃圾渗滤液

采用电解芬顿法深度处理老龄垃圾渗滤液,选取电量、进水 pH 值、进水氨氮浓度3个因素为变量,CODCr 去除率为响应值进行 Box-Behnken 中心组合设计。利用响应面法对试验结果进行分析,建立了 CODCr 去除率为响应值的二阶多项式模型并进行了方差分析和显著性检验,通过解模型逆矩阵得到最佳条件：单位面积电量为23．26 Ah／dm2、pH 值为3．58、进水氨氮浓度56．78 mg／L。在最佳条件下,CODCr 去除率为96．5％,与模型预测值偏差为4．45％,吻合度较高。对电解芬顿深度处理前后的渗滤液进行 GC-MS 分析,表明电解芬顿协同处理技术能有效降解垃圾渗滤液中难生化降解的有机物,将有机物种类从42种降低至21种,是较有效的深度处理技术。     

混凝吸附-两段SBR法处理垃圾渗滤液

利用赤泥制备复合混凝剂PAFCS(聚合硫酸氯化铝铁)并以炉渣作为吸附剂对垃圾渗滤液进行预处理,对SS和色度的去除率分别为84%和92%,对COD的去除率可达53.3%,还提高了渗滤液的可生化性.然后采用两段SBR法对垃圾渗滤液进行生化处理,结果显示通过对降解COD和氨氮的两类微生物分别进行培养,保持了较高的生物活性,进而提高了对此类高浓度难降解废水的处理效率.通过两段SBR处理以后,COD、BOD和氨氮的去除率分别为88%、94%和89%,出水水质达到了国家<生活垃圾填埋污染控制标准>(GB 16889-1997)的二级标准.     

Cu_2O/氧化石墨烯催化氧化垃圾渗滤液的因素分析

采用Cu_2O、氧化石墨烯、Cu_2O/氧化石墨烯复合催化剂处理垃圾渗滤液,分析催化剂种类、投加量、反应时间对处理效果的影响。试验结果表明,Cu_2O/氧化石墨烯复合催化剂处理垃圾渗滤液的效果最好,最佳试验条件为复合催化剂质量∶渗滤液COD质量=0.7,反应时间为1h。在最佳试验条件下,处理后的垃圾渗滤液的NH_4~+-N浓度达到2 454 mg/L,对COD的去除率可达93.33%,BOD_5/COD值为0.84。     

Fenton试剂处理垃圾渗滤液

为提高垃圾渗滤液的COD去除率,研究了Fenton试剂处理垃圾渗滤液过程中H2O2和Fe2＋的摩尔比、反应温度、pH值以及Fenton试剂的总加入量等条件对COD去除率的影响,研究发现：pH值约8.6,温度50 ℃,H2O2/Fe2＋为4,1.5倍化学计量需求量的Fenton试剂可以取得最高的COD去除率.     

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。     

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.     

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.     

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.     

Pretreatment of Afyon alcaloide factory's wastewater by wet air oxidation (WAO)

In this study, pretreatment of Afyon (Turkey) alcaloide factory wastewater, a typical high strength industrial wastewater (chemical oxygen demand (COD)=26.65 kgm(-3), biological oxygen demand (BOD(5))=3.95 kgm(-3)), was carried out by wet air oxidation process. The process was performed in a 0.75 litre specially designed bubble reactor. Experiments were conducted to see the advantages of one-stage and two-stage oxidation and the effects of pressure, pH, temperature, catalyst type, catalyst loading and air or oxygen as gas source on the oxidation of the wastewater. In addition, BOD(5)/COD ratios of the effluents, which are generally regarded as an important index of biodegradability of a high-strength industrial wastewater, were determined at the end of some runs. After a 2h oxidation (T=150 degrees C, P=0.65 MPa, airflowrate=1.57 x 10(-5)m(3)s(-1), pH=7.0), the BOD(5)/COD ratio was increased from 0.15 to above 0.5 by using the salts of metals such as Co(2+),Fe(2+),Fe(2+)+Ni(2+),Cu(2+)+Mn(2+) as catalyst.     

The effects of food waste disposers on the wastewater system: a practical study

Domestic food waste disposers (FWDs) have recently come to prominence as a possible alternative for disposal of organic waste, to reduce the quantities of this type of waste sent to landfill. There has been little research undertaken on the potential effects of food waste on the wastewater system, and it is believed no previous practical studies have been undertaken in the United Kingdom. In this study, food waste was ground in an FWD and analysed for chemical oxygen demand (COD), biological oxygen demand (BOD), ammonia, total nitrogen, total phosphorus, total suspended solids and rapidly settleable solids to determine their effects on the wastewater system. The largest impacts were on COD, BOD and suspended solids, compared with the amounts of these determinands that currently arrive at sewage treatment works (STW). Experiments using settled samples showed that a relatively high proportion of nitrogen, phosphorus, COD and BOD would pass through to secondary treatment at the STW.     

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.     

Feasibility of Treatment of Refinery Wastewater by a Pilot Scale MF/UF and UF/RO System for Reuse at Boilers and Cooling Towers

A pilot-scale hybrid membrane system, consisting of a ceramic microfilter (MF), two differentpolyvinyl chloride (PVC) and polyacrylonitrile (PAN) ultrafilters (UF), and a polyamide reverse osmosis (RO) filter, has been utilized to decrease harmful and damaging components in wastewater produced from Tehran Refinery with aim to be reused at boilers and cooling towers. Taguchi method was employed to find optimum operating conditions including transmembrane pressure, cross flow velocity (CFV), temperature, and backwash time. Further, analysis of variance (ANOVA) was performed to determine the significance of controlling factors on total organic carbon rejection and normalized permeate flux. MF (ceramic)/UF (PVC) system reduced, %: oil 99.7; chemical oxygen demand (COD) 82; biochemical oxygen demand (BOD) 79.3; conductivity 60.5; total dissolved solids (TDS) 52.6; turbidity 99.7 and total hardness 73.2. MF(ceramic)/UF (PAN) system reduced: oil, COD, BOD, conductivity, TDS, turbidity, and total hardness by 99.8; 84.2; 80.8; 62.72; 55; 99.9 and 78.4%, respectively. UF (PAN)/RO system decreased, %: oil 99.5; COD 99; BOD 99; conductivity 98; TDS 98; turbidity 98.7 and total hardness 99.94. Obtained treated wastewater by this system can be reused as feed water of boilers.     

Spatial analysis of water quality trends in the Han River basin, South Korea

Spatial patterns of water quality trends for 118 sites in the Han River basin of South Korea were examined for eight parameters-temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended sediment (SS), total phosphorus (TP), and total nitrogen (TN). A non-parametric seasonal Mann-Kendall's test determined the significance of trends for each parameter for each site between 1993 and 2002. There are no significant trends in temperature, but TN concentrations increased for the majority of the monitoring stations. DO, BOD, COD, pH, SS, and TP show increasing or decreasing trends with approximately half of the stations exhibiting no trends. Urban land cover is positively associated with increases in water pollution and included as an important explanatory variable for the variations in all water quality parameters except pH. Topography and soil factors further explain the spatial variations in pH, COD, BOD, and SS. BOD, COD, SS, and TP variations are consistently better explained by 100m buffer scale analysis, but DO are better explained by the whole basin scale analysis. Local water quality management or geology could further explain some variations of water quality. Non-point-source pollution exhibits strong positive spatial autocorrelation as measured by Moran's I, indicating that the incorporation of spatial dimensions into water quality assessment enhances our understanding of spatial patterns of water quality. The spatial regression models, compared to ordinary least square (OLS) models, always better explain the variations in water quality. This study suggests that spatial analysis of watershed data at different scales should be a vital part of identifying the fundamental spatio-temporal distribution of water quality.     

Fenton oxidation of cork cooking wastewater--overall kinetic analysis

In the present work, the possibility of using chemical oxidation through Fenton's reagent for the pre-treatment of cork cooking wastewaters was exploited. Aiming both the selection of the best operating conditions (pH, Fe2+:H2O2 ratio and initial H2O2 concentration) and the evaluation of the overall reaction kinetics, trials were performed in a batch reactor. Operating at pH = 3.2, H2O2 concentration = 10.6 g/L and Fe2+:H2O2 ratio = 1:5 (by weight), about 66.4% of total organic carbon (TOC), 87.3% of chemical oxygen demand (COD) and 70.2% of biochemical oxygen demand (BOD5) were removed and an increase of the BOD5/COD ratio from 0.27 to 0.63 was achieved. In the temperature range 20-50 degrees C, the best performance was obtained at 30 degrees C. The kinetic study was undertaken at different initial TOC concentrations and temperatures. Overall kinetics can be described by a second-order followed by a zero-order rate equation and the apparent kinetic constants at 30 degrees C are k = 2.3 x 10(-4) L/mg min and k0 = 26.0 mg/L min, respectively. The experiments performed at different temperatures confirmed the global kinetic model and allowed to calculate the global activation energy for the second-order reaction (70.7 kJ/mol).     

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.