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。     

Dedicated land disposal of wastewater sludge in south africa: leaching of trace elements and nutrients.

Most of the wastewater treatment facilities in South Africa (80%) dispose of their sewage sludge on dedicated land disposal (DLD) sites. The impact of this practice on the environment is believed to be negative, but very little research has been carried out to determine the extent of the damage to the soil and water resources. Forty wastewater treatment facilities using DLD, with different soil properties, application techniques, metal concentrations and period of sludge application, were studied. Soil and groundwater samples were collected at each of the selected facilities. Three extraction methods (aqua regia, NH4EDTA and NH4NO3) were used and samples were analysed for total N, P and K, pH, organic carbon and their metal content (Cr, Co, Ni, Cu, Zn, Cd, and Pb). Some degree of leaching of the heavy metals (especially Co and Ni) occurred at some of the sampling sites and the average depth of leaching was 100-200 mm. Deeper than 300 mm, the metal concentrations in most soil samples reached background concentrations. Seven of the nine groundwater samples that could be obtained had high NO3 concentrations (> 6 mg L(-1)). Statistical analyses of the data indicate no significant differences between sludge type (wet or dry) and leaching, or age of the disposal sites and leaching. Taking into account the age of the disposal sites, the frequency of sludge application and the metal load of the sludge, the depth of leaching is surprisingly shallow in most soils, in spite of the low soil pH(H2O) and clay content.     

Development of an ecologically sustainable wastewater treatment system

The present study aimed mainly for the development of a wastewater treatment system incorporating enhanced primary treatment, anaerobic digestion of coagulated organics, biofilm aerobic process for the removal of soluble organics and disinfection of treated water. An attempt was also made to study the reuse potential of treated water for irrigation and use of digested sludge as soil conditioner by growing marigold plants. Ferric chloride dose of 30 mg/l was found to be the optimum dose for enhanced primary treatment with removals of COD and BOD to the extent of 60% and 77%, respectively. Efficient anaerobic digestion of ferric coagulated sludge was performed at 7 days hydraulic retention time (HRT). Upflow aerobic fixed film reactor (UAFFR) was very efficient in removals of COD/BOD in the organic loading rate (OLR) range of 0.25 to 3 kg COD/m(3)/day with COD and BOD removals in the range 65-90 and 82-96, respectively. Photo-oxidation followed by disinfection saved 50% of chlorine dose required for disinfection of treated effluent and treated water was found to be suitable for irrigation. The result also indicated that anaerobically digested sludge may be an excellent soil conditioner. From the results of this study, it is possible to conclude that the developed wastewater treatment system is an attractive ecologically sustainable alternative for sewage treatment from institutional/industrial/residential campuses.     

Pilot study of a fluidized-pellet-bed technique for simultaneous solid/liquid separation and sludge thickening in a sewage treatment plant.

A fluidized-pellet-bed separator with movable sludge hoppers was applied in pilot scale for the separation and thickening of activated sludge mixture liquid. Under the condition of suspension SS around 4,000 mg/L, polymer (CJX103, cationic, MW 5 x 10(6)) dose at a dry solid ratio of 0.003 and upward flow rate at 5.4 m/hr, the fluidized pellet bed performed solid/liquid separation and sludge thickening well. The SS concentration of the treated water was about 5 mg/L on average and the moisture content of the sludge after screening for 5 min was less than 94%, which is much lower than that after conventional settling and thickening and easy to be finally disposed. At a higher upward flow rate of 7.2 m/hr, similar results could also be obtained but higher polymer dose (solid ratio of 0.004) was required. The morphological characteristics and density-size relationship of the granular particles formed in the fluidized pellet bed were also investigated by image analysis and settling velocity measurement of individual particles. The two-dimensional fractal dimension was evaluated to be 1.6-1.8, showing a good quasi-spherical morphology of the granular particles with their density much higher than the conventional flocs. The results of the pilot study indicate a possible way to innovate the conventional secondary settling and gravitational thickening processes for solid/liquid separation and sludge handling, especially for small scale wastewater treatment plants to reach the goal of space saving and higher treatment efficiency.     

Aerobic biological treatment of thermophilically digested sludge

Aerobic biological treatment of digested sludge was studied in a continuously operated laboratory set-up. An aerated reactor was filled with thermophilically digested sludge from the Moscow wastewater treatment plant and inoculated with special activated sludge. It was then operated at the chemostat mode at different flow rates. Processes of nitrification and denitrification, as well as dephosphatation, occurred simultaneously during biological aerobic treatment of thermophilically digested sludge. Under optimal conditions, organic matter degradation was 9.6%, the concentrations of ammonium nitrogen and phosphate decreased by 89 and 83%, respectively, while COD decreased by 12%. Dewaterability of digested sludge improved significantly. The processes were found to depend on hydraulic retention time, oxygen regime, and temperature. The optimal conditions were as follows: hydraulic retention time 3-4 days, temperature 30-35 degrees C, dissolved oxygen levels 0.2-0.5 mg/L at continuous aeration or 0.7-1 mg/L at intermittent aeration. Based on these findings, we propose a new combined technology of wastewater sludge treatment. The technology combines two stages: anaerobic digestion followed by aerobic biological treatment of digested sludge. The proposed technology makes it possible to degrade the sludge with conversion of approximately 45% volatile suspended solids to biogas, to improve nitrogen and phosphorus removal in reject water from sludge treatment units, and to achieve removal of malodorous substances after 8-9 days of anaerobic-aerobic sludge treatment.     

Influent flow control to increase the pollution load treated during rainy periods

The European Directive of May 1991 concerning urban wastewater treatment points out that sewerage systems must be designed to limit the pollution of receiving watercourses by stormwater discharges. As for the system management, the French Decree of 22 December 1995 states that flows or pollution loads exceeding the reference capacity of the treatment plant may be temporarily admitted. This is especially interesting in the case of separate wastewater sewerage, as inappropriate connections of runoff water and rainfall induced infiltration cause hydraulic overloads in such networks. An automated influent flow control has been implemented on a 8000 population equivalent plant to admit a maximum of twice the dry weather peak flow: the clarifier is then dynamically managed so that neither sludge loss nor degradation through anoxic conditions may occur. A yearly simulation of such a strategy on a smaller treatment plant shows a very significant reduction (90%) of the volume discharged during rainy periods. It can therefore be concluded that a plant with additional hydraulic capacity and good sludge quality can play a significant role in limiting the stormwater discharges from separate sewerage systems. However this operational benefit depends on the inflow composition in the sewerage system (wastewaters, rain and infiltration waters).     

猎德污水处理厂污泥系统除臭工程设计

根据已建污水处理厂的实际情况,对污泥浓缩池采用加高盖臭气收集方法,对污泥脱水间采用重点区域强化抽吸的臭气收集方法,并采用洗涤-生物滤床联合除臭工艺进行臭气处理;对污泥码头采用喷洒天然植物提取液除臭工艺进行除臭.介绍了除臭工程的设计参数和运行情况,工程实施后,污水处理厂的恶臭状况得到明显改善.     

Performance comparison of a pilot-scale membrane bioreactor and a full-scale sequencing batch reactor with sand filtration: treatment of low strength wastewater from a northern Canadian Aboriginal Community.

Northern Aboriginal communities in Canada suffer from poor wastewater treatment. Treatment systems on 75% of Manitoban Aboriginal communities produce substandard effluent despite the presence of sophisticated treatment systems. A 200-litre, pilot-scale membrane bioreactor (MBR) was established on the Opaskwayak Cree Nation to investigate the feasibility of MBRs in mitigating Aboriginal wastewater treatment issues. The pilot system was remote controlled and monitored via the Internet using the program pcAnywhere. The community utilized two existing sequencing batch reactors (SBR) and three sand filters for wastewater treatment. The community wastewater was relatively weak and highly fluctuating which led to poorly settling sludge that readily fouled the sand filters. A comparison study between the MBR and SBR was undertaken from September to December 2003. Operated at a 10-hour hydraulic retention time and 20-day solids residence time, the MBR outperformed the SBR and sand filtration on BOD and suspended solids removal. Furthermore, the MBR showed high levels of nitrification despite relatively cold water temperatures.     

The Ruhrverband sewage sludge disposal concept in the conflict between European and German standards and regulations.

The Ruhrverband, acting as a water association responsible for integrated water resources management within the entire natural river basin of the Ruhr, operates a network of 83 wastewater treatment plants (WWTPs) and connected sludge disposal facilities. According to German regulations, the disposal of sewage sludge containing more than 5% of organic dry solids will be prohibited as of 1 June 2005. In Germany, the only future alternative to incineration will be the agricultural utilization of sludge. However, this way of sludge disposal is presently the subject of critical discussions in Germany because of the organic and inorganic toxic substances, which may be contained in sewage sludge, despite the fact that very stringent standards are to be met by agricultural uses. On the other hand, application of sewage sludge to agricultural land is explicitly supported by the European Sewage Sludge Directive 86/278/EEC. In the face of this controversial situation the Ruhrverband has initiated, in 2000, the development of a comprehensive and sustainable sludge and waste disposal concept for all wastewater facilities it operates in the entire Ruhr River Basin. The concept includes de-central sludge digestion and dewatering and subsequent transport to two central sludge incineration plants. It is expected that in future not more than 5% of all sludges produced in Ruhrverband's WWTPs will be used in agriculture. That means, the major part of 95% will have to be incinerated.     

Analysing sludge balance in activated sludge systems with a novel mass transport model

In activated sludge systems the mechanically treated wastewater is biologically cleaned by biomass (activated sludge). The basic requirement of an efficient biological wastewater treatment is to have as a high biomass concentration in the biological reactor (BR) as possible. The activated sludge balance in activated sludge systems is controlled by the settling, thickening, scraper mechanism in the secondary settling tank (SST) and sludge returning. These processes aim at keeping maximum sludge mass in the BR and minimum sludge mass in the SST even in peak flow events (storm water flow). It can be, however, only reached by a high SST performance. The main physical processes and boundary conditions such as inhomogeneous turbulent flow, geometrical features of the SST, wastewater treatment plant (WWTP) load, return sludge flow, sludge volume index etc. all influence settling thickening and sludge returning. In the paper a novel mass transport model of an activated sludge system is presented which involves a 2-dimensional SST model coupled with a mixed reactor model of the biological reactor. It makes possible to investigate different sludge returning strategies and their influence on the sludge balance of the investigated activated sludge system, furthermore, the processes determining the flow and concentration patterns in the SST. The paper gives an overview on the first promising model results of a prevailing peak flow event investigation at the WWTP of Graz.     

Application of heat shock protein assay and proteome assay to water from wastewater treatment plant.

In this study we applied bioassay using Chinese hamster ovary (CHO) cells with a heat shock protein (HSP) 47 promoter to the effluent of the wastewater treatment plants in Sapporo and we observed the statistically significant HSP production. This implied the effluent contained some organic matter which can stress the CHO cells. To investigate the possible causes of the toxicity of the effluent, we applied the assay to the rejected water from the sludge treatment plant, the mixtures of sewage and rejected water. The evolution of HSP production during the aerobic decay process and thickening process of sludge was also examined. These assay results showed that dissolved microbial products generated and/or released from activated sludge during its decay process in the aeration tank and during thickening and dewatering process in the sludge treatment train contributed to develop HSP production. The proteomics analysis was also applied to the effluent and detected the production of elongation factor 1beta. This result implies that the effluent from wastewater treatment plants may cause changes in cell proteins involved in allergic reaction.     

Revealing microbial community structures in large- and small-scale activated sludge systems by barcoded pyrosequencing of 16S rRNA gene

The diversity of bacterial groups in activated sludge from large- and small-scale wastewater treatment plants was explored by barcoded pyrosequencing of 16S rRNA gene. Activated sludge samples (three small and 17 large scale) were collected from 12 wastewater treatment plants to clarify precise taxonomy and relative abundances. DNA was extracted, and amplified by 4 base barcoded 27f/519r primer set. The 454 Titanium (Roche) pyrosequences were obtained and analyses performed by Quantitative Insight Into Microbial Ecology (QIIME) with around 100,000 reads. Sequence statistics were computed, while constructing a phylogenetic tree and heatmap. Computed results explained total microbial diversity at phylum and class level and resolution was further extended to Operational Taxonomic Unit (OTU) based taxonomic assignment for investigating community distribution based on individual sample. Composition of sequence reads were compared and microbial community structures for large- and small-scale treatment plants were identified as major phyla (Proteobacteria and Bacteroidetes) and classes (Betaproteobacteria and Bacteroidetes). Also, family level breakdowns were explained and differences in family Nitrospiraceae and phylum Actinobacteria found at their species level were also illustrated. Thus, the pyrosequencing method provides high resolution insight into microbial community structures in activated sludge that might have been unnoticed with conventional approaches.     

Upflow anaerobic sludge blanket (UASB) treatment of supernatant of cow manure by thermal pre-treatment.

Upflow anaerobic sludge blanket (UASB) methane fermentation treatment of cow manure that was subjected to screw pressing, thermal treatment and subsequent solid-liquid separation was studied. Conducting batch scale tests at temperatures between 140 and 180 degrees C, the optimal temperature for sludge settling and the color suppression was found to be between 160-170 degrees C. UASB treatment was carried out with a supernatant obtained from the thermal treatment at the optimal conditions (170 degrees C for 30 minutes) and polymer-dosed solid-liquid separation. In the UASB treatment with a COD(Cr) loading of 11.7 kg/m3/d and water temperature of 32.2 degrees C, the COD(Cr) level dropped from 16,360 mg/L in raw water to 3,940 mg/L in treated water (COD(Cr), removal rate of 75.9%), and the methane production rate per COD(Cr) was 0.187 Nm3/kg. Using wastewater thermal-treated at the optimal conditions, also a methane fermentation treatment with a continuously stirred tank reactor (CSTR) was conducted (COD(Cr) in raw water: 38,000 mg/L, hydraulic retention time (HRT): 20 days, 35 degrees C). At the COD(Cr) loading of 1.9 kg/m3/d, the methane production rate per COD(Cr), was 0.153 Nm3/kg. This result shows that UASB treatment using thermal pre-treatment provides a COD(Cr), loading of four times or more and a methane production rate of 1.3 times higher than the CSTR treatment.     

Application of immersed MF (IMF) followed by reverse osmosis (RO) membrane for wastewater reclamation: A case study in Malaysia.

A pilot scale membrane plant was constructed and monitored in Shah Alam, Malaysia for municipal wastewater reclamation for industrial application purposes. The aim of this study was to verify its suitability under the local conditions and environmental constraints for secondary wastewater reclamation. Immersed-type crossflow microfiltration (IMF) was selected as the pretreatment step before reverse osmosis filtration. Secondary wastewater after chlorine contact tank was selected as feed water. The results indicated that the membrane system is capable of producing a filtrate meeting the requirements of both WHO drinking water standards and Malaysian Effluent Standard A. With the application of an automatic backwash process, IMF performed well in hydraulic performance with low fouling rate being achieved. The investigations showed also that chemical cleaning is still needed because of some irreversible fouling by microorganisms always remains. RO treatment with IMF pretreatment process was significantly applicable for wastewater reuse purposes and promised good hydraulic performance.     

人工湿地技术在给水工程中的应用

通过分析人工湿地技术的原理和布置,阐述其处理特点和池型布置方面的区别,并详细介绍人工湿地技术在水源生态湿地和污泥处理质能转化这两种给水工程中的应用,突出该技术在今后给水工程中广阔的应用前景.污泥处理质能转化技术在净水厂设计中可用于厂区生产排水直接处理或浓缩后排泥水处理,也可用于浓缩池上清液以及脱水机滤液达标排放处理.     

Design criteria for semi-central sanitation with low pressure network and membrane bioreactor-the ENREM project.

MBR-technology is able to fulfil similar or even higher standard for nutrients removal than conventional activated sludge processes. This paper presents the optimisation of the membrane bioreactor technology, together with a low pressure sewer, to equip a remote and yet unsewered area of Berlin requiring high quality wastewater treatment. The hydraulic flow pattern of the entire system has to be studied carefully due to the small collection system (no time delay between wastewater discharge and treatment to minimise the daily profile). The pollutant concentrations in the wastewater exhibit also stronger variations. In order to flatten out the hydraulic and load profile, and therefore to reduce the size of the biological reactor and the membrane surface, a buffer tank was installed before the MBR-plant. A full analysis of the influent hydraulic flow and wastewater characterisation is provided for the demonstration MBR-plant.     

Pretreatment and biotreatment of saline industrial wastewaters.

Wastewater from an Akzo Nobel production site contains more than 50 g/l total dissolved salts, mainly chlorides and sulphates, and is currently being treated after 10-20 x dilution. Biological treatment of undiluted or less diluted wastewater is very desirable for environmental and economic reasons. Possibilities were investigated in laboratory scale reactors to treat this highly saline and high strength wastewater aerobically, either after long adaptation or after removing part of the salts by a pretreatment. Adaptation and selection from mixed activated sludge populations took approximately 40 days to finally achieve a COD removal in aerobic treatment of 55-65% at two times dilution (11-16 g/l chloride and 5-7 g/l sulphate). Undiluted wastewater was not treatable. A higher removal percentage (> 80%) was possible at the original high salt concentration only when the sludge load was limited to approximately 0.4-0.5 kg COD/kg sludge/day. A longer adaptation time was required. Nanofiltration (NF) and crystallization could be used as a pretreatment to remove and recover up to 80% of the sulphate in the form of crystallized Glauber salt. Recovery strongly depended on the sulphate and chloride concentration in the NF concentrate and on crystallization temperature. The salt (sulphate) reduction through the NF improved the removal efficiency of a consecutive biotreatment only at a relatively low chloride level, demonstrating that the combination of nanofiltration-crystallization-aerobic biodegradation is less feasible for very saline wastewaters. Anaerobic pretreatment of saline waters turned out to be rather sensitive to high salinities. Only wastewater diluted to 10 g/l chloride could be treated well: sulphate concentration decreased by 80% and COD by 40%. Removal efficiencies of the combined anaerobic-aerobic treatment were approximately 80-85%, proving that this was a feasible route for 2-3 x diluted wastewater. The study has shown that several alternatives are available for treatment of the very saline wastewaters at a much lower degree of dilution than currently practiced.     

High COD wastewater treatment in an aerobic SBR: treatment of effluent from a small farm goat's cheese dairy.

In France, small goat's cheese dairies using traditional craft methods often have no profitable solution for dealing with the whey byproduct of their cheesemaking activity: it is usually mixed with the cleaning wastewater which, in the absence of other possibilities, is then discharged directly into the environment. The volume of such wastewater is small but it has a high COD of around 12-15 g/L. An aerobic SBR was proposed as a method for treating the mixture of wastewater and whey and the first installation was set up on a farm with 170 goats. Its operations were monitored for 7.5 months, particularly in order to measure any excess volume of sludge and to check that such excess remained within acceptable limits, given the high COD of the effluent requiring treatment. The results obtained show that the treated wastewater was of excellent quality, well within the most rigorous discharge norms. With this type of wastewater, excess sludge was produced in only very low amounts with 0.2 g of SS/g of COD. Moreover, the sludge proved to be quick settling which made it possible to: i) maintain a high level of SS in the reactor (up to 15 g/L); ii) withdraw sludge with concentrations reaching 30 g/L after 2 hours of settling. This resulted in a low volume of excess sludge (less than 5% of treated volume), making such aerobic biological treatment in an SBR competitive when compared to the straightforward spreading of all the wastewater.     

A strategy for reducing pollutants at source in order to obtain sustainable agricultural recycling of wastewater sludge

The Swedish licensing system for wastewater sludge use in agriculture, REVAQ, sets challenges. These include a maximum nominal accumulation rate of 0.2%/year on farmland, for specified metals, to be reached by 2025. Here a model is suggested, and applied for the Gothenburg regional wastewater treatment plant, Gryaab, to quantify historic sludge quality improvements and necessary future development. Local sampling campaigns covering two decades show a substantial reduction of heavy metals and ecologically harmful organic substances (such as adsorbable organic halogens, nonylphenols, phthalates, naphthalenes and polycyclic aromatic hydrocarbons) from households and society at large. For the metals studied the historic mass flow reduction to sludge varies from 1 to 2%/year for mercury, zinc and copper to 15%/year for silver. Copper needs further reduction, involving water pipes and copper roofing. Silver is rare in soil, and significant reduction from already low levels is needed to reach the accumulation goal. Further reduction of other metals involves addressing storm- and drainage water entering the sewers and the sediments already in the sewers. Fulfilling the goals of REVAQ implies national and local measures affecting public and private stakeholders including property owners, the wastewater collection system, commercial businesses and legislating authorities.     

Evaluation and testing of fine mesh sieve technologies for primary treatment of municipal wastewater.

Fine mesh sieve technologies were tested in full scale at several municipal wastewater treatment plants. A screening test was used to characterize wastewater and establish the design criteria for the sieves. To achieve high removal efficiencies it was crucial to operate the sieves with a filter mat. Rotating belt sieves performed best in the full-scale tests. A small dose of cationic polymer and a static flocculator ahead of a rotating belt sieve achieved excellent results on a wastewater that was originally found unsuitable for primary treatment with fine mesh sieves. Simple screw presses dewatered the sludge from the sieves to typically 25-30% total solids. Using fine mesh sieves with <500 microns openings was found to normally be the most economical process for primary treatment.