Relevance of the sludge retention time (SRT) as design criteria for wastewater treatment plants for the removal of endocrine disruptors and pharmaceuticals from wastewater.

Wastewater treatment plants (WWTPs) represent a significant source for the input of micro pollutants as endocrine disruptors (EDs) or pharmaceutically active compounds (PhACs) into the aquatic environment. Treatment efficiency of WWTPs often is reported, taking into account only inflow and effluent concentrations without further specification of the WWTP investigated. In order to allow comparison and evaluation of the removal efficiency of different layouts and concepts in wastewater treatment, additional information like the sludge retention time (SRT) and sludge load (F/M ratio) are necessary. Presented results from different WWTPs show correlation of removal of EDs and PhACs to the SRT. Compared to WWTPs with high F/M ratio implementation of the nitrification process on WWTPs results in a significant increase of the removal efficiency for EDs and PhACs. This paper describes an approach to determine comparable removal rates for different activated sludge systems based on mass balance and SRT.     

Impact of sludge retention time on sludge characteristics and microbial community in MBR

In this study, the impact of sludge retention time (SRT) on sludge characteristics and microbial community and the effect on membrane fouling in membrane bioreactor (MBR) was investigated. The results show that MBR with longer SRT has less fouling propensity, in agreement with other studies, despite the fact that the MBR with longer SRT contained higher MLSS and smaller particle size. However, much more soluble microbial products (SMPs) were released in MBR with shorter SRT. More slime on the membrane surface was observed in MBR with shorter SRT while sludge cakes formed on the membrane surface in MBR with longer SRT. The results show that SMP contributes to the severe fouling observed in MBR with shorter SRT, which is in agreement with other studies showing that SMPs were the major foulants in MBR. Under different SRTs of operation, the bacterial community structures of the sludge obtained by use of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) were almost identical, but those on the membrane surface differed substantially. It suggests that, although SRT has impact on sludge characteristics, it doesn't affect the microbial community in the suspension.     

Effect of 200 days' sludge retention time on performance of a pilot scale submerged membrane bioreactor for high strength industrial wastewater treatment.

A high strength industrial wastewater was treated using a pilot scale submerged membrane bioreactor (MBR) at a sludge retention time (SRT) of 200 d. The MBR was operated at a high sludge concentration of 20 g/L and a low F/M ratio of 0.11 during 300 d of operation. It was found that the MBR could achieve COD and TOC overall removal efficiencies at more than 99 and 98% TN removal. The turbidity of the permeate was consistently in the range of 0.123 to 0.136 NTU and colour254 absorbance readings varied from 0.0912 to 0.0962 a.u. cm(-1). The sludge concentration was inversely proportional to the hydraulic retention time (HRT), yielded excellent organic removal and extremely low sludge production (0.0016 kgVSS/day).     

对上海城镇污水处理厂污泥处理和处置的几点想法(上)

污泥处理和处置是解决污泥问题密不可分的两个环节,污泥如何处理、达到何种处理程度取决于污泥处置(污泥最终出路)的方式,处置决定处理.结合对上海市城镇污水处理厂污泥处理和处置的想法,阐述了污泥处理和处置的关系.     

城市污水污泥处理处置系统的技术经济分析与评价(下)

3 污泥焚烧系统的分析与评价 焚烧法是一种高温热处理技术,即以一定的过剩空气量与被处理的污泥在焚烧炉内燃烧进行氧化反应,污泥中的有机质和有毒有害物质在高温下氧化、热解而被破坏,是可同时实现污泥无害化、减量化、资源化的一种技术.在欧盟污泥焚烧比例在不断上升,并逐渐成为最主要的污泥处置手段之一[4].污泥焚烧分为污泥单独焚烧和混合焚烧,其中混合焚烧是指在水泥厂、垃圾焚烧厂、热电厂或工业锅炉与其他物料混合进行焚烧.     

Influence of solid retention time on the rheology of MBR sludge.

The rheological characterization is of crucial importance in sludge management both for biomass dewatering and stabilization purposes and for the definition of design parameters for sludge handling operations. The sludge retention time (SRT) has a significant influence on biomass properties in biological wastewater treatment systems and in particular in membrane bioreactors (MBR). The aim of this work is to compare the rheological behaviour of the biomass in a membrane bioreactor operated under different SRT. A bench scale MBR was operated for four years under the same conditions except for the SRT, that ranged from 20 days to complete sludge retention. The rheological properties were measured over time and the apparent viscosity was correlated with the concentration of solid material under equilibrium conditions. The three models most commonly adopted for rheological simulations were evaluated and compared in terms of their parameters. Steady state average values of these parameters were related to the equilibrium biomass concentration (MLSS). The models were tested to select the one better fitting the experimental data in terms of Mean Root Square Error (MRSE). The relationship between the apparent viscosity and the shear rate, as a function of solid concentration, was determined and proposed.     

净水厂生产排泥水处理工艺研究与设计

通过对净水厂生产排泥水的产生和水质特性进行分析,确定沉淀池排泥水和滤池反冲洗废水为净水厂排泥水的主要组成,结合设计干泥量的计算确定排泥水处理规模,在分析排泥水处理系统工艺流程布置特点的基础上对排泥水收集、调节、浓缩和脱水工艺进行分析,并对其中排水池、排泥池、浓缩池、平衡池、脱水工艺和场地布置的设计要点进行总结。     

Effects of complete sludge retention on biomass build-up in a membrane bioreactor.

The work reports the main results of an experimental activity aimed at evaluating the performance of a membrane bioreactor with complete sludge retention and the characteristics of its biomass. The bench scale system was started-up without any sludge inoculum and fed on real municipal sewage in order to favour biomass selection based on the imposed operating conditions. Process performance was evaluated in terms of COD removal (above 90% on average) and nitrification under two pre-determined volumetric loading rates (0.8 and 1.7 gCOD L(react)(-1), d(-1) on average). The biomass was evaluated in terms of growth, accumulation of inert solids, and bacterial activity. The latter was measured through respirometric tests. The results showed that the suspended solids concentrations (SS) under equilibrium were proportional to the volumetric loading rates in both the experimental periods considered and a relationship between these two parameters was proposed. Also, the organic loading rates reached the same equilibrium value of 0.12 gCOD gTSS(-1) d(-1) in the two periods. Moreover, the system showed very limited sludge production under equilibrium conditions (0.12 gVSS gCOD(rem)(-1) and low biomass activity, although it readily responded to load variations.     

Anaerobic treatment of a medium strength industrial wastewater at low-temperature and short hydraulic retention time: a pilot-scale experience

The aim of this work was to evaluate the performance of a pilot-scale upflow anaerobic sludge blanket (UASB) reactor during the treatment of cereal-processing industry wastewater under low-temperature conditions (17 degrees C) for more than 300 days. The applied organic loading rate (OLR(appl)) was gradually increased from 4 to 6 and 8 kg COD(sol)/m3d by increasing the influent soluble chemical oxygen demand (COD(sol)), while keeping the hydraulic retention time constant (5.2 h). The removal efficiency was high (82 to 92%) and slightly decreased after increasing the influent COD(sol) and the OLR(appl). The highest removed organic loading rate (OLR(rem)) was reached when the UASB reactor was operated at 8 kg COD(sol)/m3d and it was two times higher than that obtained for an OLR(appl) of 4 kg COD(sol)/m3d. Some disturbances were observed during the experimentation. The formation of biogas pockets in the sludge bed significantly complicated the biogas production quantification, but did not affect the reactor performance. The volatile fatty acids in the effluent were low, but increased as the OLR(appl) increased, which caused an increment of the effluent COD(sol). Anaerobic treatment at low temperature was a good option for the biological pre-treatment of cereal processing industry wastewater.     

北京市污水处理厂污泥处理与处置探讨

通过对北京市城市污水处理与污泥处理处置现况的分析,结合北京市城市污泥的特性,参照国内外污泥处理处置技术,提出适合北京市的污泥处理处置技术路线,并对北京市的污泥处置的规划原则、方案进行初步探讨,同时提出北京市污泥处置工作的建议和意见,为今后的污泥处置规划、项目建设、运行监管等提供参考。     

Effect of sludge retention time on characteristics of dynamic membrane in sequencing bioreactors

The characteristics of self-forming dynamic membrane (DM) in sequencing bioreactors under different sludge retention times (SRT) (SRT = 5, 10, 20, 40, 60 days) were studied using a scanning electron microscope, particle sizing distribution and others. The results indicated that the SRT has an evident effect on the characteristics of DM. The content of extracellular polymeric substances and protein decreased with the increase of SRT. The change of polysaccharide was small regardless of SRT. The filtration resistance of the DM was divided into two stages: an initial slowly-rising stage and a fast-rising later stage which were both irrespective of SRT. With the increase of SRT, the filtration resistance increase extent reduced and the running cycle became longer. Compared to the lower SRT, the particle size distribution of mixed liquor and DM has a decreasing trend at higher SRT. The average particle size of DM was larger than that of the mixed liquor irrespective of SRT. The amounts and types of microorganisms on the surface of DM were more abundant as SRT increased. Low SRT produced the DM surface with some Cocci while the high SRT gave the DM dominated with Cocci, Filamentous and Bacillus.     

城市污水处理厂的污泥膨胀研究分析

通过对北京市大型城市污水处理厂优势丝状菌鉴定及温度、生物选择器和溶解氧对污泥膨胀影响的研究分析,发现脱氮除磷工艺普遍会在冬季发生由Microthrix parvicella茵引起的污泥膨胀.研究了温度与SVI的变化规律,分析了出水亚硝酸氮和SVI的相关性,并对生物选择器和不同DO浓度对污泥膨胀的影响进行了分析.     

纳米颗粒在污水处理和剩余污泥处置中的迁移

纳米材料使用的日益增多,导致纳米颗粒不可避免地随污水一同进入污水处理设施.本文介绍了污水中纳米颗粒的来源,探讨了纳米颗粒在污水处理设施及剩余污泥处置过程中的迁移以及产生的影响,并在此基础上对今后的研究方向进行了展望,提出确定实际污水中纳米颗粒的环境风险及其归趋将是今后的研究重点.     

EPS对污水处理效果及污泥性能影响

通过分析EPS产生量对污水处理中多糖、蛋白质对污泥的沉降、絮凝性能及生物处理效果的影响,得出曝气0.5h COD去除率达85%,MLSS增大。EPS含量对污泥絮凝和沉降性能影响显著,随着EPS含量的增加,污泥的絮凝沉降性能变差;多糖、蛋白质含量的增加使反应器中SVI及出水浊度增加,以多糖影响为主。     

啤酒废水处理中活性污泥生物相变化研究

通过研究啤酒废水处理过程活性污泥中生物相变化的规律,探讨了生物相的变化与COD去除率的相互关系。废水处理采用摇瓶培养法,原生动物测定采用显微镜直接计数法,细菌、霉菌、放线菌采用平板菌落计数法。在接种后前2 d细菌数量呈快速上升,随后进入缓慢下降期。放线菌、霉菌在整个处理期数量略有下降且变化不大;小型纤毛虫其生长规律与典型的细菌生长曲线相似;主要原生动物出现的先后顺序是:小型纤毛虫,然后轮虫和变形虫;受生物相变化的影响,体系中COD值在前4 d下降较快,随后下降变慢。研究表明:原生动物在啤酒废水处理中数量的变化很大,可以作为废水处理COD值减小的指示生物。     

Symbiotic algal bacterial wastewater treatment: effect of food to microorganism ratio and hydraulic retention time on the process performance.

Algal incorporation into the biomass is important in an innovative wastewater treatment that exploits the symbiosis between bacterial activated sludge and microalgae (Chlorella vulgaris sp. Hamburg). It allows a good and easy algae separation by means of clarification. The effect of process parameters food to microorganisms ratio (F/M) and hydraulic retention time (HRT) on the process performance, evaluated by settleability, microalgae incorporation to biomass and nutrient removal, was studied. HRT hinted at a significant influence in the growth rate of algae, while F/M turned out to be important for stability when algae are incorporated into the biomass. This parameter also affects the total nitrogen removal of the treatment. Stable flocs with incorporated algae and supernatants with low free swimming algae concentrations were obtained at high HRT and low F/M values.     

Effects of hydraulic retention time,temperature, and effluent recycling on efficiency of anaerobic filter in treating rural domestic wastewater

With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time(HRT), temperature, and effluent recycling on the treatment efficiency of an anaerobic filter(AF) reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18℃, 21℃, and 24℃, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67℃, 30.57℃, and 26.91℃; and three effluent recycling ratios of 1:1, 1:2, and 2:1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for +4NH-N, 19% to 23% for 3NO-N-, and 12% to 22% for TP. In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for +4NH-N, 30% to 34% for 3NO-N-, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30℃, and an effluent recycling ratio of 2:1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling.     

我国污水处理厂污泥含砂特征及成因调研

对我国南方某市7座污水处理厂脱水污泥固体组成进行调研,并从污水处理厂进水水质、砂的粒度分布、沉砂池效率及二级处理有机负荷角度进行污泥泥质成因分析。调研结果表明,该市污水处理厂污泥有机质含量整体较低,砂含量偏高,并随季节有一定规律变化。污水处理厂进水含砂量高、砂的粒度小,沉砂池效率低,二级处理污泥有机负荷低是污泥有机质含量低、含砂量高的主要原因。     

Disinfection of sludge using lime stabilisation and pasteurisation in a small wastewater treatment plant.

Removal efficiency of faecal coliforms and helminth eggs was evaluated in a small wastewater treatment plant (WWTP) serving a population of 1,000. This system was formed by the association in series of a UASB reactor and four submerged aerated biofilters. The density of faecal coliforms and the count of helminth eggs were estimated in the liquid and solid phases of the system. Two different methods of disinfecting sludge were investigated: (a) chemical treatment with lime and (b) a physical treatment by pasteurisation. As expected, the association UASB + BF was very efficient at removal of helminth eggs from the final tertiary effluent, but coliforms were still present at high densities. Lime treatment and pasteurisation of sludge were very effective methods of disinfection and produced a sludge safe for final disposal.     

好氧颗粒污泥处理高浓度及难降解废水研究进展

好氧颗粒污泥以其在反应器中污泥沉降速度快、泥水分离简单、污泥浓度高,能够同时实现脱氮除磷等特点成为目前污(废)水处理领域的研究热点之一。对好氧颗粒污泥在高浓度有机废水及难降解废水(硝基苯废水、苯酚废水、氯酚废水、苯胺和氯苯胺废水、含盐废水、染料废水)处理中的研究现状进行综述,重点探讨了好氧颗粒污泥处理该类物质的影响因素、去除机制及其微生物特性等,指出其在难降解废水处理方面具有良好的应用前景。