Aerobic treatment of concentrated wastewater in a submerged bed reactor

The performance of an aerobic submerged bed reactor applied to the treatment of a concentrated effluent was assessed. The wastewater employed was diluted stillage of alcohol distilleries, presenting a COD content of 3000–3500 mg l⁻¹. The reactor was continuously operated during 200 days, corresponding to five residence times varying from 23 to 4.5 h. The results show that 60–80% of COD removal may be obtained with 10–16 h of residence time. The advantages of this type of reactor are pointed out and suggestions of improvement are also presented.     

Combined aerobic heterotrophic oxidation, nitrification and denitrification in a permeable-support biofilm

A biofilm reactor, termed the permeable-support biofilm (PSB), was developed in which oxygen was supplied to the interior of the biofilm through a permeable membrane. The reactor was tested on filtered sewage supplemented with nutrient broth; the bulk solution was anoxic and the interior of the biofilm was supplied with pure oxygen. All tests were performed on a non-steady state biofilm with a depth of 1 mm. Mass balances on total organic carbon, ammonia, organic nitrogen and nitrate showed that combined heterotrophic oxidation of organics, denitrification and nitrification occurred simultaneously within the biofilm. The advantages of such a reactor are discussed.     

Nitrogen dynamics and removal in a horizontal flow biofilm reactor for wastewater treatment

A horizontal flow biofilm reactor (HFBR) designed for the treatment of synthetic wastewater (SWW) was studied to examine the spatial distribution and dynamics of nitrogen transformation processes. Detailed analyses of bulk water and biomass samples, giving substrate and proportions of ammonia oxidising bacteria (AOB) and nitrite oxidising bacteria (NOB) gradients in the HFBR, were carried out using chemical analyses, sensor rate measurements and molecular techniques. Based on these results, proposals for the design of HFBR systems are presented.The HFBR comprised a stack of 60 polystyrene sheets with 10-mm deep frustums. SWW was intermittently dosed at two points, Sheets 1 and 38, in a 2 to 1 volume ratio respectively. Removals of 85.7% COD, 97.4% 5-day biochemical oxygen demand (BOD₅) and 61.7% TN were recorded during the study.In the nitrification zones of the HFBR, which were separated by a step-feed zone, little variation in nitrification activity was found, despite decreasing in situ ammonia concentrations. The results further indicate significant simultaneous nitrification and denitrification (SND) activity in the nitrifying zones of the HFBR. Sensor measurements showed a linear increase in potential nitrification rates at temperatures between 7 and 16 °C, and similar rates of nitrification were measured at concentrations between 1 and 20 mg NH₄-N/l. These results can be used to optimise HFBR reactor design. The HFBR technology could provide an alternative, low maintenance, economically efficient system for carbon and nitrogen removal for low flow wastewater discharges.     

High-rate anaerobic treatment of Fischer-Tropsch wastewater in a packed-bed biofilm reactor

This study investigates the anaerobic treatment of an industrial wastewater from a Fischer-Tropsch (FT) process in a continuous-flow packed-bed biofilm reactor operated under mesophilic conditions (35 °C). The considered synthetic wastewater has an overall chemical oxygen demand (COD) concentration of around 28 g/L, mainly due to alcohols. A gradual increase of the organic load rate (OLR), from 3.4 gCOD/L/d up to 20 gCOD/L/d, was adopted in order to overcome potential inhibitory effects due to long-chain alcohols (>C6). At the highest applied OLR (i.e., 20 gCOD/L/d) and a hydraulic retention time of 1.4 d, the COD removal was 96% with nearly complete conversion of the removed COD into methane. By considering a potential of 200 tCOD/d to be treated, this would correspond to a net production of electric energy of about 8 × 10⁷ kWh/year.During stable reactor operation, a COD balance and batch tests showed that about 80% of the converted COD was directly metabolized through H₂⁻ and acetate-releasing reactions, which proceeded in close syntrophic cooperation with hydrogenotrophic and acetoclastic methanogenesis (contributing to about 33% and 54% of overall methane production, respectively). Finally, energetic considerations indicated that propionic acid oxidation was the metabolic conversion step most dependent on the syntrophic partnership of hydrogenotrophic methanogens and accordingly the most susceptible to variations of the applied OLR or toxicity effects.     

Performance characteristics of the anaerobic baffled reactor

An anaerobic sludge blanket process, termed the anaerobic baffled reactor (ABR), has been developed and shows promise for industrial wastewater treatment. It combines the advantages of high stability and reliability with a high void volume. The risk of clogging and sludge bed expansion with resulting high microbial losses is reduced and there is no need for special gas collection or biological solids separation systems. Organic loadings as high as 36 g COD l^?1day^?1 have been achieved with COD removal rates of more than 24 g COD l^?1 day^?1 and methane production rates exceeding 6 volumes per day per unit volume of reactor. The hypothesis, that the ABR may be adequately modeled as a fixed-film reactor, has been supported. Therefore, a unified approach, based on fundamentals of bacterial kinetics and mass transport, appears useful for modeling this and similar systems. Pilot plant studies are necessary to determine the scaling factors of the system as well as the overall efficiency and costs.     

The use of an upflow fixed bed reactor for treatment of a primary settled domestic sewage

This study presents and demonstrates results obtained from an half full-scale upflow fixed bed reactor (UFBR) treating a primary settled domestic sewage. This study used expanded clay with an effective size of 2.7 mm containing hematite and magnetite as a granular medium.The content of TSS in the effluent treated was always between 10 and 20 mg l⁻¹ for bed depths ranging from 2 to 3 m and filtration rates of 3–6 m³m⁻²h⁻¹.The profiles taken all along the reactor show that the activity of the biomass is constant over the whole height of the reactor. Moreover, an air/water volume ratio of 2:1 is amply sufficient to satisfy the oxygen demand of the biomass. The average removal efficiency based on the soluble COD remains virtually unchanged as a function of the filtration rate at about 70% of the influent. For a final BOD₅ of 30 mg l⁻¹, loadings of 4.5–8 kg BOD₅m⁻³ can be applied. This corresponds to filtration rates of 3–6 m³m⁻²h⁻¹. The removal efficiencies for BOD₅ are then about 80%.After optimization of the backwashing conditions, the consumption of backwash water is about 5% of the volume of filtered water.Sludge measurements carried out during our experiments indicate an excess sludge production of 1 kg kg⁻¹ BOD₅ eliminated. The nature of these sludges is very similar to the biological sludges produced in the high rate activated sludge process.This study has made it possible to establish design parameters of an UFBR and to develop technology for applications. These results are applied to two wastewater treatment plants which began to operate in 1984: these plants serve population equivalents of 40,000 and 11,000.     

浙江某工业废水处理厂升级改造运行效果解析

浙江某工业废水处理厂升级改造,采用AAO—MBBR复合生物膜工艺,在未新增建设用地和扩建池容的基础上,日处理量由3×10⁴m³/d提高至6×10⁴m³/d。改造后实际运行出水COD、TP、NH₃-N和TN浓度分别为(37.7±6.61)、(0.09±0.03)、(0.25±0.14)和(5.87±1.54)mg/L,出水水质稳定达到一级A标准。实际监测表明,在好氧MBBR区存在TN去除现象,约占TN总去除量的10.36%。系统内的优势硝化菌属为硝化螺旋菌属Nitrospira,其在悬浮载体生物膜和活性污泥中的相对丰度分别为8.98%和0.92%,悬浮载体的投加使硝化细菌得到有效富集;反硝化菌在生物膜中的占比为7.94%,为悬浮载体同步硝化反硝化(SND)效果的发生提供了微观保证,提高了TN去除率。     

以氯化方法实现生物膜法短程硝化反应

以稳定运行的全程硝化的生物膜反应器的一个反应单元为研究对象,通过外加氯实现对硝化反应中两类细菌的选择性抑制。分别以冲击性和连续性方式投加氯,可以在生物膜法生物脱氮反应中实现短程硝化。当短程硝化反应实现后,通过改变投药方式可节省投药量并维持短程硝化反应。     

Leachate treatment with nitrification of ammonia

Results are presented on the treatment of leachate to remove ammonia by biological nitrification. Outdoor activated sludge and trickling filter pilot plants were operated for 2 years at a major co-disposal landfill. Leachate ammonia nitrogen concentrations ranged from 150 to 550 mg l^?1 while TOC concentrations ranged from 200 to 500 mg l^?1. Very little of the TOC was degradable and BOD: NH₃-N ratios were typically 1:3.Nitrification was successfully established in both plants, and curves were established for the response of the kinetics to different temperatures. Maximum ammonia removal rate in the activated sludge plant was at least 131 g N kg VSS^?1 day^?1 achieved at an average temperature of 13°C. Maximum removal rate in the trickling filter was 309 mg N m^?2 day^?1, at 16°C.Operating problems and strategies for full-scale treatment are discussed.     

有机物浓度对复合反应器生化降解特性的影响

本试验在连续运行的条件下,考察了C／N对连续运行的复合生物反应系统有机物、氨氮去除效果的影响,结果表明,复合生物反应器在试验运行条件下,对COD,NH3一N的去除率都在90％以上,其中的生物膜对去除效果起主要作用。但C／N在30左右时,系统会发生污泥膨胀,且随着C／N的增加,污泥膨胀发生的更加频繁。     

Behaviour of an anaerobic expanded bed reactor in non-steady state conditions

This paper presents a series of experimental data on an expanded bed anaerobic reactor operating at high organic loading rates in non-steady state conditions.The first four experiments were conducted in start-up periods after shut-downs. In the section dedicated to behaviour in the face of fluctuations, two experiments with overloading, two with decrease in temperature and one with air inflow, have been included. In all cases, the reactor demonstrated great stability with short recovery periods.     

好氧生物膜过滤装置的研究

研究开发了一种新型好氧生物膜过滤装置 ,能有效地降低污水中的CODCr、BOD5、NH3-N和SS等。二级处理后出水再经该装置处理后 ,水质达到《生活杂用水水质标准》(CJ 2 5.1— 1989) ,有显著的社会、环境和经济效益     

Enhancing nitrification in vertical flow constructed wetland utilizing a passive air pump

Nitrification of simulated secondary effluent solution using a variant of the vertical flow bed constructed wetland was studied. In this system oxygen required for the nitrification process is supplied by a passive air pump. The passive air pump is based on a fill and draw cycle, where oxygen depleted air is removed from the system while fresh air is introduced. Each volume of effluent drained is displaced by an equal volume of fresh air. Spatial and temporal oxygen distribution in the system as a function of drained effluent volume was investigated. Experimental results of nitrification and the corresponding oxygen consumption show good agreement with theoretical calculations based on physico–chemical considerations. Observations show that while oxygen distribution within the media was found to be non-uniform at the beginning of each cycle, it approached more uniform distribution with time. The latter resulted mainly from diffusion of oxygen in the gaseous phase.     

移动床生物膜反应器处理高温聚氯乙烯母液废水

采用工业化规模的移动床生物膜反应器(MBBR)处理高温聚氯乙烯(PVC)母液废水,试验结果表明,在反应器进水温度为44～55℃、设计流量为80m3/h、水力停留时间为32h、气水比为(10～15):1的条件下,处理后出水COD≤30mg/L,NH4 -N≤5mg/L,浊度≤10 NTU.对反应器进行了1年的考察发现,反应器运行稳定,抗冲击负荷能力强,且温度对COD处理效果的影响不明显.     

三相生物流化床中生物膜厚度研究

通过工业规模的三相生物流化床试验,探讨了载体表面生物膜厚度与有机物去除速率、容积负荷及污泥浓度等传统参数之间的必然联系,证实了生物膜厚度是描述反应器行为的关键参数,揭示了三相生物流化床高处理效率的实质是微生物浓度高,并得到最佳膜厚为９０￣１１０μｍ。     

Treatment of easily degradable wastewater in a stirred anaerobic sequencing batch biofilm reactor

The main objectives of this study were to evaluate the performance of an anaerobic sequencing batch reactor when subjected to a progressive increase of influent glucose concentration and to estimate the kinetic parameters of glucose degradation. The reactor was initially operated in 8-h cycles, treating glucose in concentrations of 500, 1000 and 2000 mg l(-1). No glucose was detected in the effluent under these three conditions. The reactor showed operating stability when treating a glucose concentration of approximately 500 mg l(-1), with filtered chemical oxygen demand (COD) removal efficiencies varying from 93% to 97%. Operational instability occurred in the operation with glucose concentrations of approximately 1000 and 2000 mg l(-1), caused mainly by a production of extracellular polymeric substances (EPS), which led to hydrodynamic and mass transfer problems in the reactor. The mean volatile acid concentration values in the effluent were approximately 159+/-72 and 374+/-92 mg l(-1), respectively. A first-order model was adjusted to glucose concentration profiles and a modified model, including a residual concentration of substrate, was adjusted to COD temporal profiles. To check the formation of EPS, the reactor was operated in 3-h cycles with concentrations of 500 and 1000 mg l(-1). The purpose of this step was to discover if the production of EPS resulted from the biomass's exposure to a low concentration of substrate over a long period of time. Thus, it was hypothesized that a reduction of the time cycle would also reduce the exposure to low concentrations. However, this hypothesis could not be confirmed because large amounts of EPS were formed already under the first operational condition, using approximately 500 mg l(-1) of glucose in the influent, thus indicating the fallacy of the hypothesis. The production of EPS proved to depend on the organic volumetric load applied to the reactor.     

低DO紊动床内有机物对硝化过程的影响

利用生物紊动床在低溶解氧（DO）和有机物存在的条件下研究了氨氮的亚硝化、硝化和有机物氧化的规律，分析了异养菌与自养菌竞争的特点。试验结果表明，DO为2－3mg/L、有机物浓度（TOC）为200mg/L、C／N＝1：1．5时对硝化作用影响不大；DO为0.5-1mg/L、TOC≥mg/L、C／N＝1：3时硝化系统即受到破坏。     

节地型HBR生物膜技术在贵阳金百再生水厂的应用

贵阳金百再生水厂设计规模为3.0×10⁴m³/d,出水水质执行《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准,就近作为麦架河河道生态补水。生化处理采用节地型生物膜技术,通过悬浮填料和高填充率的固定床结构,实现生物膜处理和生物过滤的双重作用,高效去除污染物,省去二沉池,节省占地面积。介绍了该厂的工艺流程、构筑物设计及设备配置情况,并对运行效果进行总结。自运行以来,出水水质稳定达标,COD、SS、氨氮、总氮、总磷去除率分别为89.4%、92.8%、96.3%、48.4%、90.9%;节地效果明显,吨水占地仅为0.36 m²/(m³·d^-1);运行成本为0.56元/m³,与同等规模的传统活性污泥法污水厂的运行成本相近。     

Anaerobic treatment of real textile wastewater with a fluidized bed reactor

Anaerobic treatability of a real cotton textile wastewater was investigated in a fluidized bed reactor (FBR) with pumice as the support material. The immobilized biomass or attached volatile solids level on the support material was 0.073 g VSS/g support material at the end of the 128-d start-up period. During the operation period, real cotton textile wastewater was fed to the anaerobic FBR both unsupplemented (in Stages 1 and 2) and supplemented (with synthetic municipal wastewater in Stage 3 and glucose in Stages 4-6). The effect of operational conditions such as organic loading rate (OLR), hydraulic retention time (HRT), influent glucose concentration as the co-substrate, etc. was investigated to achieve the maximum color removal efficiency in the reactor. Results indicated that anaerobic treatment of textile wastewater studied was possible with the supplementation of an external carbon source in the form of glucose (about 2g/l). The corresponding maximum COD, BOD(5) and color removals were found to be around 82%, 94% and 59%, respectively, for HRT of around 24h and OLR of 3 kg COD/m(3)/d. Further increase in external carbon source added to real textile wastewater did not improve the color removal efficiency of the anaerobic FBR reactor.     

Simultaneous nitrification/denitrification in a biofilm airlift suspension (BAS) reactor with biodegradable carrier material

Simultaneous nitrification and denitrification in one reactor has been realized with different methods in the past. The usage of biodegradable biocompounds as biofilm carriers is new. The biocompounds were designed out of two polymers having different degradability. Together with suspended autotrophic biomass the biocompound particles were fluidized in an airlift reactor. Process water from sludge dewatering with a mean ammonium nitrogen concentration of 1150 mg L⁻¹ was treated in a two stage system which achieved a nitrogen removal of 75%. Batch experiments clearly indicate that nitrification can be localized in the suspended biomass and denitrification in the pore structure of the slowly degraded biocompounds. Images taken with CLSM prove the concept of the pore structure within the biocompounds, which provide both a heterotrophic biofilm and carbon source.