一体化反应器处理生活污水的中试研究

鉴于污水处理中对氮、磷去除率的要求和内循环三相生物流化床反应器存在的不足,开发了一种一体化高效分离生物流化复合反应器(HSBCR)。HSBCR反应器好氧循环流化区采用了独特的分格结构,并且在同一个反应器中实现了好氧、缺氧分区运行。HSBCR中试设备处理生活污水的结果表明,当反应器好氧区HRT为1h时,出水COD质量浓度可以达到《城镇污水处理厂污染物排放标准》(GB18918-2002)的二级标准;当HRT为2h,出水COD质量浓度可以达到一级(B)排放标准。随着HRT从1h延长到2.5h,反应器对NH3-N的去除效果上升;对TN的去除效果表明,反应器具有较好的反硝化效果;反应器生物除磷效果对TP有约50%的去除率。利用HSBCR进行同步化学除磷可以使反应器出水TP低于1.0mg/L;气浮分离使反应器出水SS有效控制在20mg/L以内。     

Competition between planktonic and fixed microorganisms during the start-up of methanogenic biofilm reactors

The influence of the hydraulic retention time (HRT) on the start-up phase of a methanogenic inverse turbulent bed bioreactor was investigated. Two identical reactors were monitored, the only differing parameter being the HRT: one of the reactors was fed with a diluted wastewater at a constant HRT of 1 day, the organic loading rate (OLR) being increased by decreasing the substrate dilution; the second reactor was fed at a constant influent concentration of 20 g COD L(-1), the OLR being increased by decreasing the HRT from 40 days to 1 day. After 45 days of start-up, both reactors were operated at an OLR of 20 g COD L(-1)d(-1) and a HRT of 1 day. However, strong differences were observed on biofilm growth. In the reactor operated at a constant short HRT, biofilm concentration was 4.5 as high as in the reactor operated at an increasing HRT. This difference was attributed to the competition between planktonic and biofilm microorganisms in the latter reactor, whereas suspended biomass was quickly washed out in the former reactor because of the low HRT.     

生物滤池/生态砾石床处理含氮微污染地表水

采用生物滤池/生态砾石床组合工艺进行了微污染地表水(含低碳、高NO3--N浓度)的脱氮研究,通过投加乙酸钠为碳源考察了C/N值、温度、水力负荷对反应器脱氮效能的影响。结果表明,C/N值对反应器的脱氮效能影响较大,在C/N值为10时可以取得较高的反硝化效率(>90%)。在低温下(2～10℃)反应器的反硝化效能受到严重抑制;在13～17℃条件下,反硝化效率恢复到60%左右;当水温>20℃时,在水力负荷为8 m3/(m2.h)的条件下(此时生物滤池和生态砾石床的水力停留时间分别为15、30 min),对NO3--N的去除率能够达到90%以上。生态砾石床能够将生物滤池出水中残余的碳源去除,保证了出水的水质安全。     

济宁污水处理厂升级改造中试研究

针对山东省济宁污水处理厂存在的氮磷脱除效率低与运行稳定性差等问题,应用MBBR工艺系统进行了中试规模的强化脱氮除磷现场试验研究,分析了水力停留时间、填料填充率及外源性碳源对系统处理效果的影响．试验结果表明：在常温条件下,中试系统的COD、NH4^＋-N、TN、TP平均去除率分别达到80．56％,92．5％,46．3％和65．6％,处理效果优于同期污水处理厂处理效果;工艺控制参数不变,投加外源性碳源（甲醇）33mg／L,中试系统TN去除率由46．3％提高到72．4％,出水TN小于10mg／L,同时中试系统出水COD有所降低．本研究为济宁污水处理厂的升级改造提供了重要技术依据．     

硫酸盐还原对活性污泥沉降性能的影响

采用双SBR和人工配水进行试验,考察了厌氧选择器中硫酸盐还原对好氧反应器内活性污泥沉降性能的影响。结果表明,当进水硫酸盐浓度一定时,厌氧选择器的水力停留时间越长,则硫酸盐的还原程度越高;当厌氧选择器的水力停留时间一定时,进水的硫酸盐浓度越高,则硫酸盐的还原程度越高。当进水硫酸盐浓度为85 mg/L、在厌氧选择器水力停留时间为60 min时,好氧反应器内已有污泥膨胀迹象;当进水硫酸盐浓度为125 mg/L、在厌氧选择器水力停留时间为60min时,好氧反应器内开始发生污泥膨胀,镜检发现活性污泥中存在大量丝状菌;当进水硫酸盐浓度为250 mg/L、在厌氧选择器水力停留时间为20 min时,好氧反应器内活性污泥膨胀严重,反应器内污泥浓度降低,出水漏泥现象严重,影响到反应器的处理效果。     

Effect of process configuration and substrate complexity on the performance of anaerobic processes

The roles of substrate complexity (molecular size of the substrate) and process configuration in anaerobic wastewater treatment were investigated to determine optimal methanogenic technology parameters. Five substrates (glucose, propionate, butyrate, ethanol, and lactate) plus a mixed waste (60% carbohydrate, 34% protein, and 6% lipids) were studied under five reactor configurations: batch-fed single-stage continuous stirred tank reactor (CSTR), continuously fed single-stage CSTR, two-phase CSTR, two-stage CSTR, and single-stage upflow anaerobic sludge blanket (UASB). The substrate feed concentration was 20,000 mg/L as COD. The solids retention time (SRT) and hydraulic retention time (HRT) in the CSTR reactors were 20 d, while HRT in the UASB was 2 d. All reactors were operated for at least 60 d (equal to 3SRT). Substrate complexity was observed to be less significant under two-phase, two-stage and UASB reactor configurations. Two-phase CSTR, two-stage CSTR, and single-stage UASB configurations yielded the lowest effluent chemical oxygen demands (130-550, 60-700, and 50-250 mg/L, respectively). The highest effluent chemical oxygen demands were detected when feeding glucose, propionate, and lactate to continuously fed single-stage CSTRs (10, 400, 9900, and 4700 mg/L COD, respectively) and to batch-fed single-stage CSTRs (11, 200, 2500, and 2700 mg/L COD, respectively). Ironically, the one stage CSTR--most commonly utilized in the field--was the worst possible reactor configuration.     

Effect of hydraulic retention time on sulfate reduction in a carbon monoxide fed thermophilic gas lift reactor

Thermophilic hydrogenogenic carbon monoxide (CO) converting microorganisms present in anaerobic sludge play a crucial role in the application of CO as electron donor for sulfate reduction. Hydrogenogenic CO conversion was investigated in a gas lift reactor (55 degrees C) at different hydraulic retention times (HRT). Operation at a HRT>9h resulted in predominant consumption of CO-derived H2 by methanogens (up to 90%) and thus in a poor sulfate reduction efficiency of less than 15%. At HRTs<4 h, consumption of the CO-derived H2 was dominated by sulfate-reducers, i.e. up to 95% of H2 was used for sulfate reduction. Sulfate reduction rates of 17 mmol L(-1)d(-1) were achieved at a HRT of 3h, with over 87% of the H2 produced used for sulfate reduction. Methane production, however, persisted when operating under these conditions and increasing the HRT by returning it to values >5.5h resulted in a dominance of methanogenesis over sulfate reduction. The sulfate reduction rates were limited by the amount of CO supplied and its conversion efficiency (about 85%) at higher CO loads likely resulting from a low biomass retention.     

Biological hydrogen production by Clostridium acetobutylicum in an unsaturated flow reactor

A mesophilic unsaturated flow (trickle bed) reactor was designed and tested for H2 production via fermentation of glucose. The reactor consisted of a column packed with glass beads and inoculated with a pure culture (Clostridium acetobutylicum ATCC 824). A defined medium containing glucose was fed at a flow rate of 1.6 mL/min (0.096 L/h) into the capped reactor, producing a hydraulic retention time of 2.1 min. Gas-phase H2 concentrations were constant, averaging 74 +/- 3% for all conditions tested. H2 production rates increased from 89 to 220 mL/hL of reactor when influent glucose concentrations were varied from 1.0 to 10.5 g/L. Specific H2 production rate ranged from 680 to 1270 mL/g glucose per liter of reactor (total volume). The H2 yield was 15-27%, based on a theoretical limit by fermentation of 4 moles of H2 from 1 mole of glucose. The major fermentation by-products in the liquid effluent were acetate and butyrate. The reactor rapidly (within 60-72 h) became clogged with biomass, requiring manual cleaning of the system. In order to make long-term operation of the reactor feasible, biofilm accumulation in the reactor will need to be controlled through some process such as backwashing. These tests using an unsaturated flow reactor demonstrate the feasibility of the process to produce high H2 gas concentrations in a trickle-bed type of reactor. A likely application of this reactor technology could be H2 gas recovery from pre-treatment of high carbohydrate-containing wastewaters.     

预处理/厌氧生物处理敌百虫生产废水的研究

对敌百虫生产废水的处理工艺进行了研究,先采用破乳法和电解法进行预处理,然后再采用升流式厌氧污泥床(UASB)工艺进行厌氧处理,试验历时90 d,考察了系统的稳定性及pH值、温度和水力停留时间(HRT)等对反应器的影响。结果表明,当温度控制在30～35℃、pH值为6.8～7.5、进水COD为12 000 mg/L、HRT为72 h时,对COD的去除率可达到73%以上;厌氧处理后采用除磷药剂进行混凝沉淀,出水总磷浓度降为618 mg/L,对总磷的去除率为75.36%。     

Treatment of anaerobically pre-treated domestic sewage by a rotating biological contactor.

The performance of a rotating biological contactor (RBC) for the post-treatment of the effluent of an up-flow anaerobic sludge blanket (UASB) was the subject of this study. Different hydraulic and organic loading rates have been investigated. The removal efficiencies of COD(total), COD(suspended), COD(colloidal) and COD(soluble) increased at a higher hydraulic retention time (HRT) and a lower influent organic loading rate. The results obtained indicated that a two-stage RBC reactor at an HRT of 10 h and an organic loading rate of 6.4g COD m(-2) d(-1) represents an effective post-treatment process. Most COD(suspended) and COD(colloidal) were removed in the first stage while nitrification proceeded in the second stage. The overall nitrification efficiency was 92% at an ammonia loading rate of 1.1 gm(-2) d(-1). Total E. coli removal at HRTs of 10, 5 and 2.5h were 99.5%, 99.0% and 89.0%. respectively. The major part of suspended E. coli ( >4.4 microm) was removed by sedimentation or by adsorption in the biofilm of the first stage of RBC (99.66%). However, E. coli in the colloidal fraction (<4.4 to >0.45 microm) was eliminated in the second stage of RBC (99.78%). A comparison of the performance of a one-stage versus two-stage RBC system, operated at the same total loading rate, revealed an improvement in the effluent quality of the two-stage effluent as compared to the one-stage effluent. The two stages RBC were used to examine the effect of hydraulic shock loads on reactor performance in terms of COD, nitrification and E. coli removal.     

Oilfield wastewater treatment by combined microfiltration and biological processes.

This work deals with the treatment of offshore oilfield wastewater from the Campos Basin (Rio de Janeiro State, Brazil). After coarse filtration, this high saline wastewater was microfiltrated through mixed cellulose ester (MCE) membranes, resulting in average removals of COD, TOC, O&G and phenols of 35%, 25%, 92% and 35%, respectively. The permeate effluent was fed into a 1-L air-lift reactor containing polystyrene particles of 2mm diameter, used as support material. This reactor was operated for 210 days, at three hydraulic retention times (HRT): 48, 24 and 12h. Even when operated at the lowest HRT (12 h), removal efficiencies of 65% COD, 80% TOC, 65% phenols and 40% ammonium were attained. The final effluent presented COD and TOC values of 230 and 55 mg/L, respectively. Results obtained by gas chromatography analyses and toxicity tests with Artemia salina showed that a significant improvement in the effluent's quality was achieved after treatment by the combined (microfiltration/biological) process.     

Seasonal variability of the reduction in estrogenic activity at a municipal WWTP

In vitro monitored estrogenicity of municipal wastewater influent/effluent samples (collected from September to December from a Northern Canadian biological nutrient removal (BNR) treatment plant serving an urban population of 750,000) were combined with operational, wastewater quality, and climate data to determine which of these latter variables may be related to the levels and reduction in the former parameter. Significant variability was present in operational and wastewater quality parameters throughout the sampling period including a 7 degrees C difference in wastewater temperature Most of the wastewater samples collected during this period show a considerable amount of recombinant yeast assay (RYA) activity with the greatest activity (estradiol (E2)-equivalents of 106-175ng/L) seen in the final effluents collected from mid-September to mid-October. Percent reduction in the levels of RYA measured E2-equivalents varied from -234% to 75%. No correlations were seen in RYA activity reduction with percent reduction in 5-day biochemical oxygen demand (BOD(5)), flow (i.e. inversely related to hydraulic retention time), solids retention time or even rainfall, and the reduction trends for RYA measured activity were explained best by ambient and effluent temperatures in an inverse fashion (% reduction in E2-equivalents=-10.8.(effluent temperature in degrees C)+191, p=0.005). Complementary instrumental analysis of select sample composites revealed that the free/conjugated estrogen ratio was indeed greater in the wastewater sampled during warmer temperatures.     

Increased biological hydrogen production with reduced organic loading

An experimental matrix consisting of reactor hydraulic retention time (HRT) and glucose loading rate was tested to understand the effect of organic loading on H2 production in chemostat reactors. In order to vary the glucose loading rate over a range of 0.5-18.9 g/h, the glucose concentration in the feed was varied from 2.5 to 10 gCOD/L under conditions where the HRT varied from 1 to 10 h (30 degrees C, pH=5.5). Decreasing the glucose loading rate over this range increased the hydrogen yield from 1.7 to 2.8 mol-H2/mol-glucose. High yields of hydrogen were consistent with a high molar acetate:butyrate ratio of 1.08:1 as more hydrogen is produced with acetate as a product (4 mol-H2/mol-acetate) than with butyrate (2 mol-H2/mol-butyrate). It was thought that the decrease in yield with organic loading rate resulted from an overall decreased rate of hydrogen production. As the rate of gas production is reduced, H2 supersaturation in the liquid phase is likely reduced, relieving inhibition due to H2. Flocculation was also an important factor in the performance of the reactor. At the 5-10 gCOD/L influent glucose concentrations, substantial flocculation was observed particularly as the feeding rate was increased due to a reduction in the HRT from 10 to 2.5 h. At the HRT of 2.5 h, biomass concentrations reached as much as 25 g/L. The flocculant nature of the biomass allowed reactor operation at low HRTs with steady H2 production and >90% glucose removal. However, when the HRT was reduced to 1 h at a glucose feed concentration of 2.5 gCOD/L, there was little flocculation evident resulting in wash-out of the culture. These results suggest that hydrogen yields will be optimized for more dilute feeds and lower organic loading rates than have typically been used in biohydrogen reactor studies.     

Removal of carbon and nutrients from domestic wastewater using a low investment, integrated treatment concept

An integrated chemical-physical-biological treatment concept for the low-cost treatment of domestic wastewater is proposed. Domestic wastewater was subjected to a chemically enhanced primary treatment (CEPT), followed by treatment in an upflow anaerobic sludge blanket (UASB) reactor. In addition, a regenerable zeolite was used to remove NH4+, either after CEPT pretreatment or after biological treatment in the UASB reactor. The CEPT pretreatment consisted of the addition of a coagulant (FeCl3) and an anionic organic flocculant and removed on average 73% of the total chemical oxygen demand (COD(t)), 85% of the total suspended solids, and 80% of PO4(3-) present in the wastewater. The UASB system, which consequently received a low COD(t) input of approximately 140 mg/L, was operated using a volumetric loading rate of 0.4 g COD(t)/L. d (hydraulic retention time [HRT]=10 h) and 0.7 g COD(t)/L. d (HRT=5 h). For these conditions, the system removed about 55% of the COD(t) in its influent, thus producing an effluent with a low COD(t) of approximately 50 mg/L. The zeolite, when applied in batch mode before the UASB reactor, removed approximately 45% of the NH4+, whereas its application as a post-treatment cartridge resulted in almost 100% NH4+ removal. The simple design and relatively low operating costs, due to low costs of added chemicals and low energy input (estimated at Euro 0.07-0.1 per m3 wastewater treated), combined with excellent treatment performance, means that this system can be used as a novel domestic wastewater treatment system for developing countries. Therefore, the system is called a Low Investment Sewage Treatment (LIST) system.     

High-rate denitrification and SS rejection by biofilm-electrode reactor (BER) combined with microfiltration

In this study, a multi-cathode biofilm-electrode reactor (BER) combined with microfiltration (MF) was investigated using a laboratory-scale experimental apparatus for treatment of nitrate-contaminated water. The multi-cathode electrodes were composed of multiple-granular activated carbons (GACs). GACs attached to each cathode to enlarge surface area of electrodes and to attach bacteria quickly and firmly. In BER, H2 gas is produced by applying electric current, which serves as an electron donor in biological reduction of nitrate to N2 gas. Since some suspended solids were escaping from BER, MF membrane with plate modules and a pore size of 0.2 microm was placed after BER. Experimental results demonstrated that it was possible to operate the multi-cathode BER with high denitrification rates and hydraulic retention time (HRT) as low as HRT = 20 min. The denitrification rate was enhanced by 3-60 times in comparison with former studies. MF membrane successfully rejected the bacteria escaping from BER, so that the effluent concentration of SS was kept below 1 mg SS/l throughout the experiment. It was also possible to operate MF membrane at flux 2-9 times higher and pressure 2.5-31 times smaller than in former studies. This higher performance was mainly brought about by using biofilm and H2 gas as an electron donor. Also, an economic evaluation of BER/MF was included, showing the feasibility of this process. The present BER/MF process is considered advantageous for the enhanced treatment of nitrate-polluted groundwater.     

水力停留时间对BAF除污性能的影响

研究了水力停留时间(HRT)对曝气生物滤池(BAF)除污效果的影响。结果表明:HRT对BAF处理效果的影响较大,当HRT为0.63 h时,出水浊度、COD、氨氮和总氮浓度均较高,BAF的除污效果较差;当HRT为0.83 h时,出水COD浓度可降至50 mg/L以下,去除率可达到85.87%;当HRT为1.0 h时,BAF对浊度、氨氮和总氮均有较好的去除效果,去除率分别为95.98%7、7.08%4、0.09%,出水浊度<4 NTU、氨氮<8 mg/L、总氮<35 mg/L。     

Saline sewage treatment using a submerged anaerobic membrane reactor (SAMBR): Effects of activated carbon addition and biogas-sparging time

This study investigated the performance of a submerged anaerobic membrane reactor (SAMBR) treating saline sewage under fluctuating concentrations of salinity (0-35 g NaCl/L), at 8 and 20 h HRT, with fluxes ranging from 5-8 litres per square metre per hour (LMH). The SAMBRs attained a 99% removal of Dissolved Organic Carbon (DOC) with 35 g NaCl/L, while removal inside the reactor was significantly lower (40-60% DOC). Even with a sudden drop in salinity overall removal recovered quickly, while the recovery inside the reactor took place at a slower rate. This highlights the positive effect of the membrane in preventing the presence of high molecular weight organics in the effluent while also retaining biomass inside the reactor so that they can rapidly acclimatize to salinity. The reduction of continuous biogas sparging to intervals of 10 min ON and 5 min OFF resulted in a slight increase in transmembrane pressure (TMP) by 0.025 bar, but also resulted in an increase in effluent DOC removal and inside the SAMBR by 10% and 20%, respectively. The addition of powdered activated carbon (PAC) resulted in a decrease in the TMP by 0.070 bar, and an increase in DOC removal in the reactor and effluent by 30% and 5%, respectively. The PAC dramatically decreased the high molecular weight organics in the reactor over a period of 72 h. SEM pictures of the membrane and biomass before and after addition of PAC revealed a remarkable reduction of flocks on the membrane surface, and a reduction inside the reactor of soluble microbial products (SMPs). Finally, Energy Dispersive X-ray (EDX) analysis of the membranes pores and biofilm highlighted the absence of organic matter in the inner pores of the membrane.     

Biodegradation of distillery spent wash in anaerobic hybrid reactor

A lab-scale anaerobic hybrid (combining sludge blanket and filter) reactor was operated in a continuous mode to study anaerobic biodegradation of distillery-spent wash. The study demonstrated that at optimum hydraulic retention time (HRT), 5 days and organic loading rate (OLR), 8.7kgCOD/m(3)d, the COD removal efficiency of the reactor was 79%. The anaerobic reduction of sulfate increases sulfide concentration, which inhibited the metabolism of methanogens and reduced the performance of the reactors. The kinetics of biomass growth i.e. yield coefficient (Y,0.0532) and decay coefficient (K(d), 0.0041d(-1)) was obtained using Lawrence and McCarty model. However, this model failed in determining the kinetics of substrate utilization. Bhatia et al. model having inbuilt provision of process inhibition described the kinetics of substrate utilization, i.e. maximum rate of substrate utilization (R,1.945d(-1)) and inhibition coefficient values (K(i),0.032L/mg). Modeling of the reactor demonstrated that Parkin and Speece, and Bhatia et al. models, both, could be used to predict the effluent substrate concentration. However, Parkin and Speece model predicts effluent COD more precisely (within +/-2%) than Bhatia et al. model (within +/-5-20%) of the experimental value. Karhadkar et al. model predicted biogas yield within +/-5% of the experimental value.     

缺氧─好氧工艺处理印染废水的试验研究

对缺氧─好氧工艺处理印染废水可行性进行了试验研究，取得了工程设计所需的试验数据．研究表明：当进水ＣＯＤ＝１８００ｍｇ／Ｌ，ｐＨ＝１０．０～１０．８，水力停留时间ＨＲＴ＝１３ｈ，则系统出水ＣＯＤ＝２７０ｍｇ／Ｌ，ＣＯＤ平均去除率为８５％．其中二级缺氧段在水力停留时间仅为３．８５ｈ的情况下，使废水ＢＯＤ５／ＣＯＤ由进水０．２左右提高到０．４６～０．４８，ｐＨ值由１０．０～１０．８下降至７．６～８．３，为后续好氧处理创造了有利条件，这是本试验流程能够有效地处理该印染废水的关键．     

DAT-IAT改进工艺对生活污水中氨氮的去除

以需氧池-间歇曝气池（DAT-IAT）工艺为基础，在其后设置一生物接触氧化反应器，考察了该组合工艺对生活污水中氨氮的去除效果。结果表明，在IAT池以曝气2h、沉淀1h、出水1h的工况运行及生物接触氧化反应器的HRT为3h的条件下，系统对氨氮的平均去除率为81．1％，出水氨氮平均浓度为7．0mg／L，满足《城市污水再生利用城市杂用水水质》（GB／T 18920-2002）的要求。系统对氨氮的去除率随着进水COD浓度的提高而下降，当进水COD为815．3mg／L时，出水氨氮浓度仍可满足GB／T 18920-2002的要求；随着进水氨氮浓度的提高，系统对氨氮的去除率先略有上升后明显下降，为保证出水氨氮浓度达到回用标准，应将进水氨氮浓度控制在50mg／L以下；系统适宜的pH值范围为7～8，pH值过高或过低都会造成系统对氨氮去除率的显著下降。