Aerobic and anaerobic membrane bioreactors for municipal wastewater treatment.

An aerobic bioreactor and an anaerobic bioreactor, each coupled with a microfiltration membrane filter (MBR), were operated at different hydraulic retention times (HRTs) with primary effluent from the City of Elmhurst, Illinois, municipal-wastewater-treatment plant. The soluble chemical oxygen demand (COD) removal performance of the anaerobic MBR system was similar to that of the aerobic MBR under the same operational conditions, without the added cost of aeration. The results indicated that the solids deposition rate on the membrane surface was lower in the case of anaerobic MBR compared to the aerobic MBR, indicating possible lower loss in water-flux rates. This research found that an anaerobic MBR is a feasible and economical option for municipal-wastewater-treatment plants seeking COD removal by a biological process followed by a separate nitrification and denitrification system.     

A modified UCT method for biological nutrient removal: configuration and performance

A pilot-scale prototype activated sludge system is presented, which combines both, the idea of University of Cape Town (UCT) concept and the step denitrification cascade for removal of carbon, nitrogen and phosphorus. The experimental set-up consists of an anaerobic selector and stepwise feeding in subsequent three identical pairs of anoxic and oxic tanks. Raw wastewater with influent flow rates ranging between 48 and 168 l d(-1) was fed to the unit at hydraulic residence times (HRTs) of 5-18 h and was distributed at percentages of 60/25/15%, 40/30/30% and 25/40/35% to the anaerobic selector, 2nd and 3rd anoxic tanks, respectively (influent flow distribution before the anaerobic selector). The results for the entire experimental period showed high removal efficiencies of organic matter of 89% as total chemical oxygen demand removal and 95% removal for biochemical oxygen demand, 90% removal of total Kjeldahl nitrogen and total nitrogen removal through denitrification of 73%, mean phosphorus removal of 67%, as well as excellent settleability. The highest removal efficiency and the optimum performance were recorded at an HRT of about 9h and influent flow rate of 96 l d(-1), in which 60% is distributed to the anaerobic selector, 25% to the second anoxic tank and 15% to the last anoxic tank. Consequently, the plant configuration enhanced removal efficiency, optimized performance, saved energy, formed good settling sludge and provided operational assurance.     

Effect of limited aeration on the anaerobic treatment of evaporator condensate from a sulfite pulp mill

Serious inhibition was found in the regular up-flow anaerobic sludge blanket (UASB) reactor in treating the evaporator condensate from a sulfite pulp mill, which contained high strength sulfur compounds. After applying the direct limited aeration in the UASB, the inhibition was alleviated gradually and the activity of the microorganisms was recovered. The COD removal rate increased from 40% to 80% at the organic loading rate of 8kgCODm(-3)d(-1) and a hydraulic retention time of 12h. Limited aeration caused no oxygen inhibition to the anaerobic microorganisms but instigated sulfide oxidization and H(2)S removal, which was beneficial to the methanogens. The experiment confirmed the feasibility of applying limited aeration in the anaerobic reactor to alleviate the sulfide inhibition. It also proved that the anaerobic system was actually aerotolerant. SEM observation showed that the predominant microorganisms partly changed from rod-shaped methanogens to cocci after the UASB reactor was aerated.     

Simultaneous nitrification and denitrification of municipal wastewater in aerobic membrane bioreactors.

Simultaneous nitrification-denitrification (SND) of municipal wastewater was investigated in a laboratory-scale membrane bioreactor (MBR) operated at two different hydraulic retention times (HRTs), 0.5 and 1 day, dissolved oxygen 3.0 to 0.5 mg/L, and solids retention time (SRT) between 28 and 120 days. The organic loading rate (OLR) (0.11 to 0.64 kg chemical oxygen demand [COD]/m3/d) and influent soluble COD (SCOD)/ total Kjeldahl nitrogen (TKN) ratio (5 to 19) were varied by the addition of glucose. The ammonia-nitrogen and TKN removals were over 97%, and total nitrogen removal was approximately 89% in the MBR. The maximum specific nitrification rates (98 mg N/d/g VSS) and specific denitrification rates (81 mg N/d/g VSS) occurred at an SCOD/TKN ratio of 9.1. The optimum conditions for maximum total nitrogen removal by SND in a single reactor MBR have been found to be low dissolved oxygen (< 0.6 mg/L) and high OLR (approximately 0.64 kg COD/m3/d) at an HRT of 0.5 day and SRT of approximately 85 days.     

间歇曝气潜流人工湿地的污水脱氮效果

采用间歇曝气运行方式,提升潜流人工湿地生活污水处理系统中的溶解氧浓度,强化脱氮效果。结果表明,间歇曝气运行方式有效提高了湿地内部溶解氧水平,曝气时溶解氧浓度可达6~9 mg/L,停止曝气后,溶解氧浓度迅速下降至0.5 mg/L以下,在湿地内部营造了一种交替的好氧和缺氧环境,分别促进好氧硝化和缺氧反硝化作用。在水力停留时间为3 d的情况下,间歇曝气潜流人工湿地系统对氨氮、总氮和COD的去除率分别可达到98.0%、87.6%和96.3%,较常规潜流人工湿地系统分别提高了74.1%、56.4%和18.1%,实现了氨氮、总氮和COD的同步高效去除。     

pH-gradient real-time aeration control for nitritation community selection in a non-porous hollow fiber membrane biofilm reactor (MBfR) with dilute wastewater

Nitritation (ammonium to nitrite) as a pre-treatment of Anammox (anaerobic ammonium oxidation) is a key step for an energy-efficient nitrogen-removal alternative from dilute wastewaters, e.g. anaerobically-treated sewage, with which limited study has achieved sustainable nitritation at ambient temperature and short hydraulic retention times. To this end, pH-gradient real-time aeration control in an oxygen-based membrane biofilm reactor was observed at 20 °C in the sequencing batch mode. An optimum oxygen supply via diffusion for ammonium-oxidizing bacteria (AOB) was established, but nitrite-oxidizing bacteria (NOB) could be inhibited. The system achieved nitrite accumulation efficiencies varying from 88% to 94% with the aeration control. Mass balance and rate performance analyses indicate that this aeration control is able to supply an oxygen rate of 1.5 mol O₂ mol^?1 ammonium fed, the benchmark oxygenation rate based on stoichiometry for nitritation community selection. Microbial analyses confirmed AOB prevalence with NOB inhibition under this aeration control.     

生物脱氮工艺控制优化策略的研究进展

针对传统的单污泥生物脱氮系统具有所需反应器体积大、硝化反硝化效率低及对进水COD利用率低等一系列问题 ,总结了提高生物脱氮工艺效率的在线控制策略 ,如曝气控制、外投碳源控制和污泥龄控制 (SRT) ,为当前污水厂在工艺设计一定的限制性条件下进行在线优化以满足日益严格的排放标准提供了重要保证。     

Bioenergy production from diluted poultry manure and microbial consortium inside Anaerobic Sludge Bed Reactor at sub-mesophilic conditions

In this study, anaerobic treatability of diluted chicken manure (with an influent feed ratio of 1 kg of fresh chicken manure to 6 L of tap water) was investigated in a lab-scale anaerobic sludge bed (ASB) reactor inoculated with granular seed sludge. The ASB reactor was operated at ambient temperature (17–25°C) in order to avoid the need of external heating up to higher operating temperatures (e.g., up to 35°C for mesophilic digestion). Since heat requirement for raising the temperature of incoming feed for digestion is eliminated, energy recovery from anaerobic treatment of chicken manure could be realized with less operating costs. Average biogas production rates were calculated ca. 210 and 242 L per kg of organic matter removed from the ASB reactor at average hydraulic retention times (HRTs) of 13 and 8.6 days, respectively. Moreover, average chemical oxygen demand (COD) removal of ca. 89% was observed with suspended solids removal more than 97% from the effluent of the ASB reactor. Influent ammonia, on the other hand, did not indicate any free ammonia inhibition due to dilution of the raw manure while pH and alkalinity results showed stability during the study. Microbial quantification results indicated that as the number of bacterial community decreased, the amount of Archaea increased through the effective digestion volume of the ASB reactor. Moreover, the number of methanogens displayed an uptrend like archaeal community and a strong correlation (?0.645) was found between methanogenic community and volatile fatty acid (VFA) concentration especially acetate.     

Optimization of the intermittent aeration in a full-scale wastewater treatment plant biological reactor for nitrogen removal.

The optimization of the intermittent aeration in a full-scale biological reactor treating municipal and industrial wastewater has been studied by means of an experimental design, where the main factors considered have been the on-off period of aeration and the dissolved-oxygen set point. The objective of the work has been to determine the optimal configuration of the aeration control to achieve a simultaneous removal of carbon (expressed as chemical oxygen demand [COD]) and nitrogen. The results were obtained in a full-scale bioreactor located at the wastewater treatment plant of Sant Celoni (Barcelona, Spain), where a nitrogen removal based on a nitrification-denitrification process is being tested. It has been shown that the crucial parameter to ensure a complete removal of COD and nitrogen is to give the system a long time of on-off aeration to complete both the nitrification and the denitrification processes, whereas the dissolved-oxygen set point has a minor influence on the overall performance. The results presented can be applied to a great number of similar systems, in which a nitrogen removal, based on a nitrification-denitrification scheme, is currently being tested or implemented.     

曝气沉砂池除砂机理分析

针对曝气沉砂池小试装置模型，通过配砂实验对沉砂池除砂率进行统计分析，研究曝气强度与HRT对沉砂池除砂率的影响。实验结果表明，不同曝气强度下，随着HRT变化，除砂率逐渐上升，并最终趋于平衡状态；不同HRT下，曝气强度与除砂率近似呈现一定的线性关系，且随着曝气强度的增大，除砂率降低；在HRT小于1min时，砂粒的运行路径和沉降时间缩短，不利于砂粒的去除；在HRT大于1min时，其中1、3和4min，随着气水比的增加除砂率降低幅度相对较小，曝气所引起的横向环流在一定程度上有利于砂粒的沉降，而HRT为2min时，除砂率降幅却很大，这与砂粒在曝气沉砂池池体断面分布有关，即断面处旋转流速和水平流速的大小变化将影响砂粒的运动；相比曝气强度，HRT对除砂率的影响较大。     

Effects of reduced return activated sludge flows and volume on anaerobic zone performance for a septic wastewater biological phosphorus removal system.

Enhanced biological phosphorous removal (EBPR) performance was found to be adequate with reduced return-activated sludge (RAS) flows (50% of available RAS) to the anaerobic tank and smaller-than-typical anaerobic zone volume (1.08 hours hydraulic retention time [HRT]). Three identical parallel biological nutrient removal pilot plants were fed with strong, highly fermented (160 mg/L volatile fatty acids [VFAs]), domestic and industrial wastewater from a full-scale wastewater treatment facility. The pilot plants were operated at 100, 50, 40, and 25% RAS (percent of available RAS) flows to the anaerobic tank, with the remaining RAS to the anoxic tank. In addition, varying anaerobic HRT (1.08 and 1.5 hours) and increased hydraulic loading (35% increase) were examined. The study was divided into four phases, and the effect of these process variations on EBPR were studied by having one different variable between two identical systems. The most significant conclusion was that returning part of the RAS to the anaerobic zone did not decrease EBPR performance; instead, it changed the location of phosphorous release and uptake. Bringing less RAS to the anaerobic and more to the anoxic tank decreased anaerobic phosphorus release and increased anoxic phosphorus release (or decreased anoxic phosphorus uptake). Equally important is that, with VFA-rich influent wastewater, excessive anaerobic volume was shown to hurt overall phosphorus removal, even when it resulted in increased anaerobic phosphorus release.     

Performance of a submerged membrane bioreactor system for biological nutrient removal.

A pilot submerged membrane bioreactor coupled with biological nutrient removal was used to treat the primary effluent at a municipal wastewater treatment plant. Long-term experiments were conducted by varying hydraulic retention time from 6 to 8 hours and solids retention time from 20 to 50 days, respectively. The performance was assessed by monitoring key wastewater parameters, including chemical oxygen demand (COD), nitrogen, and phosphorus concentration in individual anoxic, anaerobic, aerobic, and membrane separation zones. Results showed that the tested system can consistently achieve COD, nitrogen, and phosphorus removal efficiencies at 80 to 98%, 70 to 93%, and 89 to 98%, respectively. Effluent COD remained low as a result of efficient solid retention, even though there was great variation in influent quality. However, total nitrogen increased proportionally with influent concentration. At a 50-day solids retention time, higher COD and nitrogen oxides specific utilization rates in the anoxic zone resulted in a high production of nitrogen oxides in the subsequent aerobic zone.     

Removal of organic and nitrogen and molecular weight distribution of residual soluble organic from entrapped mixed microbial cells and activated sludge processes.

The simultaneous removal of organic and nitrogen and molecular weight distribution (MWD) of residual soluble chemical oxygen demand (RSCOD) in final effluent were investigated using entrapped mixed microbial cells (EMMC) and conventional activated sludge processes. Two different types of processes using EMMC carriers demonstrated better organic and nitrogen removal performance because of the high solids retention time (SRT) compared with the activated sludge process. Regarding the RSCOD, the longer SRT process (EMMC) was affected by reducing the hydraulic retention time, resulting in the increase of high-molecular-weight materials. On the other hand, reducing the aeration period had significantly affected the MWD in the shorter SRT process (activated sludge), resulting in an increase of low-molecular-weight materials.     

微污染水源水生物处理工艺中IAL-CHS与三相流化床的初步比较

初步比较气升式内循环蜂窝陶瓷反应器(IAL-CHS)和内循环三相流化床反应器(ITFB)对微污染水源水进行生物预处理的效果。IAL-CHS反应器比ITFB反应器挂膜启动速度快,但是在挂膜期承受冲击负荷能力较ITFB反应器差。在进水相同条件下,两者所能达到的最小水力停留时间、最大体积负荷和容积负荷相差不大,但是ITFB反应器的曝气强度却为IAL-CHS反应器的3.33倍,并且比IAL-CHS反应器出水SS高,浊度去除率低,单位载体的生物量及活性生物量小。     

Effect of initial pH control on enhanced biological phosphorus removal from wastewater containing acetic and propionic acids

In the literature most of the studies on the effect of pH on enhanced biological phosphorous removal were conducted with the acetate wastewater, and the pH was controlled during the entire anaerobic and aerobic stages. This paper investigated the influence of anaerobic initial pH control, which will be more practical than the entire process pH control strategy, on enhanced biological phosphorus removal from wastewater containing acetic and propionic acids. Typical pH profile showed that both the initial alkaline and acidic pH tended to neutralize due to the consumption of short-chain fatty acid (SCFA) and intracellular pH regulation by polyphosphate accumulating organisms (PAOs). It was observed that the glycogen degradation and polyhydroxyalkanoates (PHA) accumulation decreased with increasing initial pH, which disagreed with previous reports. In the literature the metabolisms of both glycogen and PHA by PAOs in the acetate wastewater were independent of pH. An anaerobic mechanism model was proposed to explain the intra- and extra-cellular pH buffer nature of PAOs, and to address the reasons for increased polyphosphate degradation and decreased PHA synthesis and glycogen degradation at higher pH. The optimal initial pH for higher soluble ortho-phosphorus (SOP) removal efficiency should be controlled between 6.4 and 7.2. This pH control strategy will be easier to use in practice of wastewater treatment plant.     

Thermal hydrolysis of secondary scum for control of biological foam.

Thermal hydrolysis of secondary scum at 9 bars and 170 degrees C was shown to completely destroy Gordonia sp. cells and reduce its foaming potential, so that it can be recycled to headworks or sent to the solids-handling side of the plant without the risk of causing foaming problems in the activated sludge system and anaerobic digesters. This process shows promise for biological foam control in wastewater treatment plants where solids retention time control and selective wasting cannot be applied and/or selector installation is not possible. An initial cost comparison of thermal hydrolysis and several widely accepted foam-management strategies shows it to be competitive; however, optimization of operating pressure and temperature is necessary.     

竹制填料生物接触氧化工艺处理污染河水

针对受污染的湖溪河水质特征，以传统弹性塑料填料做对比，研究以竹球和竹丝为填料的生物接触氧化工艺，考察填料的挂膜时间、生物量和污水处理效果；确定连续曝气和间歇曝气时反应器的最优运行工况：连续曝气时为HRT：7．5h，DO=3mg／L；间歇曝气时为厌氧1．2h、好氧6．3h交替运行。实验结果表明，与弹性塑料填料相比，竹制填料挂膜速度快，竹球填料的水处理效果最好；连续曝气最优工况下竹球填料反应器中COD、TN、NH3-N和TP的平均去除率分别为66．7％、47．9％、57．1％和30．6％；间歇曝气最优工况下竹球填料反应器中COD、TN、NH3-N和TP的平均去除率分别64．08％、39．95％、60．7％和54．68％；竹制填料可替代传统的塑料填料作为生物接触氧化工艺的载体填料。     

膜生物反应器处理生活污水无泡供氧研究

用疏水性微孔膜制成的供氧器，向水溶液或发酵液供氧时，无气泡产生，这种无泡式供氧方式突破了传统的泡式供氧模式，具有传氧效率高，无泡沫产生和动力消耗低等优点，在膜生物反应器中用无泡式供氧进行生活污水处理试验研究，结果表明，它对生活污水中CODcr、BOD5、NH3－N、SS、大肠杆菌等都具有较好的去除效果。     

Anaerobic treatment of slaughterhouse wastewater: a review

This article presents a review of anaerobic treatment technologies to treat slaughterhouse wastewater including its advantages and disadvantages. Physico-chemical characteristics and biochemical methane potential (BMP) of slaughterhouse wastewater are addressed. Various anaerobic treatment technologies are presented with the related operating parameters, viz., hydraulic retention time (HRT), organic loading rate (OLR), upflow velocity (V_up), and biogas yield vis-a-vis treatment efficiency in terms of chemical oxygen demand (COD). In addition, various factors that affect the anaerobic treatment of slaughterhouse wastewater such as high oil & grease (O & G) concentration in influent, inhibitors, volatile fatty acids (VFAs), and the loading rate are also addressed. The literature review indicated that the slaughterhouse wastewater can be treated effectively by employing any anaerobic treatment technologies at OLRs up to 5 kg COD/m³.d with more than 80% COD removal efficiency without experiencing operational problems. Anaerobic hybrid reactors (AHRs) were found the most effective among various reviewed technologies because of their ability to operate at higher OLRs (8 to 20 kg COD/m³.d) and lower HRTs (8 to 12 hrs).

     

Ozone disintegration of excess biomass and application to nitrogen removal.

A pilot-scale facility integrated with an ozonation unit was built to investigate the feasibility of using ozone-disintegration byproducts of wasted biomass as a carbon source for denitrification. Ozonation of biomass resulted in mass reduction by mineralization as well as by ozone-disintegrated biosolids recycling. Approximately 50% of wasted solids were recovered as available organic matter (ozonolysate), which included nonsettleable microparticles and soluble fractions. Microparticles were observed in abundance at relatively low levels of ozone doses, while soluble fractions became dominant at higher levels of ozone doses in ozone-disintegrated organics. Batch denitrification experiments showed that the ozonolysate could be used as a carbon source with a maximum denitrification rate of 3.66 mg nitrogen (N)/g volatile suspended solids (VSS) x h. Ozonolysate was also proven to enhance total nitrogen removal efficiency in the pilot-scale treatment facility. An optimal chemical oxygen demand (COD)-to-nitrogen ratio for complete denitrification was estimated as 5.13 g COD/g N. The nitrogen-removal performance of the modified intermittently decanted extended aeration process dependent on an external carbon supply could be described as a function of solids retention time.