悬浮填料技术用于污水处理厂二级出水极限脱氮研究

采用悬浮填料技术对城镇污水处理厂二级出水进行极限脱氮研究,分析填充比、水温及硝酸盐氮表面负荷等关键因素对悬浮填料技术极限脱氮性能的影响,考察悬浮填料技术极限脱氮效果.结果表明,填料填充比宜控制在35％～50％,当水温23～27 ℃,硝酸盐氮表面负荷可控制为2.5 gNO3--N/(m2·d),HRT为30 min,当水...     

Combined chemical analyses and biomonitoring at Avedoere wastewater treatment plant in 2002.

Influent--effluent monitoring by comprehensive chemical analyses was conducted at the Avedoere wastewater treatment plant (WWTP) during 2002. In one programme, the same samples were tested for algal toxicity by the ISO 8692 method. Based on evaluation of 17 hazardous substances (including 7 heavy metals), there was a quite good agreement between calculated and measured toxic units. In another programme, influent--effluent monitoring for 11 pharmaceuticals and specific hormones showed high removal rates, except for sulphamethizol and furosemide. High removal is probably due to WWTP operation with long SRTs. Effluent biomonitoring of freshwater mussels showed only bioaccumulation for: diethylphthalate, LAS, EOX as well as Cr and Ni. Surprisingly, no bioaccumulation could be observed for 100 other specific organic compounds and 8 other heavy metals (including Hg, Cd and Pb).     

Application of a sponge media (BioCube) process for upgrading and expansion of existing caprolactam wastewater treatment plant for nitrogen removal.

For the upgrade and expansion of an existing caprolactam wastewater treatment plant, a freely floating sponge media (BioCube) process was selected based on extensive pilot-plant tests, due to extreme space constraints. In order to protect nitrifier inhibition caused by high strength organics in caprolactam wastewater, the pilot plant consisted of an organics removal reactor, which functioned as a pretreatment for nitrification, and followed the nitrogen removal reactor. The suspended MLSS was 1,800-4,000 and the media attached MLSS was maintained at 22,000-26,000 mg/L. The final effluent COD was noticeably low, around 20.4-37 mg/L, even with fairly large fluctuations in the feed levels, between 1,400-6,770 mg/L. The removal of total nitrogen with the system, when denitrification was close to completion, was approximately 97.6%. For the entire run, complete nitrification of 99.6% was achieved, which might have been due to well-acclimatized nitrifiers attached in the BioCube media. Specifically, after adaptation, the nitrification continuously increased in the organics removal reactor, even under high residual organics conditions. From the numerous experimental results, the BioCube process seemed to be an effective method for the upgrading and expansion of the existing wastewater treatment plant, with minimum reactor enlargement.     

Treatment of municipal wastewater in a hybrid process using a new suspended carrier with large surface area.

An activated sludge/biofilm hybrid process treating municipal wastewater was studied in pilot plant trials. A new type of suspended carrier, with large effective surface area, was employed in the process with the aim of enhancing nitrification. The pilot plant was operated for 1.5 years in five different configurations including pre-denitrification in all five and enhanced biological phosphorus removal in the final two. The wastewater temperature ranged between 11 degrees C and 20 degrees C, and the nominal dissolved oxygen (DO) level was 5-6 mg/L. The nitrification rate obtained on the new carrier within the hybrid stage was in the range of 0.9-1.2 g NH4-N/m2/d corresponding to a volumetric rate of 19-23 g NH4-N/m3/h (total nitrification including nitrification in the suspended solids). More than 80% of the total nitrification took place on the carrier (and the remainder in the suspended solids). The nitrification rate was shown to correlate with DO, decreasing when the DO was decreased. The results supported the idea of using the new carrier as a tool to upgrade plants not having nitrification today or improve nitrification in activated sludge processes not reaching necessary discharge levels. The large surface area present for nitrification makes it possible to obtain high nitrification rates within limited volumes. The possibility to keep the total suspended solid content low (< 3 g/L) and avoiding problems with the filament Microthrix parvicella, are other beneficial properties of the hybrid process.     

Stability analysis of a wastewater treatment plant with saturated control.

This paper presents a saturated proportional controller that achieves depollution of wastewater in a continuous anaerobic digester. This goal is reached by defining a region of the state-space where the depollution is achieved and forcing attractivity and invariance of this region. The control variable is the dilution rate and the controlled variable is a linear combination (S(lambda)) of the substrates concentrations, that could be the chemical oxygen demand or the biological oxygen demand, depending on the value of A. No measurement of the substrates concentrations in the input flow is required: the only necessary measurement is S(lambda).     

Modeling of a large-scale wastewater treatment plant for efficient operation.

Environmental legislations in the Western world impose stringent effluent quality standards for ultimate protection of the environment. This is also observed in Turkey. The current paper presents efforts made to simulate an existing 0.77 million m3/day conventional activated sludge plant located at Ankara, AWTP. The ASM1 model was used for simulation in this study. The model contains numerous stoichiometric and kinetic parameters, some of which need to be determined on case by case bases. The easily degradable COD (S(S)) was determined by two methods, physical-chemical and respirometric methods, namely. The latter method was deemed unreliable and rejected in the further study. Dynamic simulation with SSSP program predicted effluent COD and MLSS values successfully while overestimating OUR. A complete fit could only be obtained by introducing a dimensionless correction factor (etaO2 = 0.58) to the oxygen term in ASM1.     

Application of chemical precipitation for piggery wastewater treatment.

Several series of experiments were conducted to investigate the treatment of piggery wastewater using chemical precipitation (CP) where various types of coagulants such as aluminium sulfate (Al2(SO4)3), poly aluminium chloride (PAC), ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), ferrous sulfate (FeSO4) and ferrous chloride (FeCl2) were used. Throughout the experiments, CP was found to achieve high removal efficiencies for organic compounds and nutrients (nitrogen and phosphorus) from the piggery wastewater. Experimental results showed the optimal doses of FeCl3, Fe2(SO4)3, FeCl2 and FeSO4 was 2.0 g/L, while 0.31 g/L and 2.5 g/L were the optimum dose for PAC and Al2(SO4)3, respectively. The pH range 4-5 resulted in the best performance to all coagulants except FeCl2 and FeSO4, whose optimum pH were more than 6. Percentage removal efficiencies for COD were in the ranges of 70-80%, 90-95% for SS, 80-90% for organic-N and TP. Those removal efficiencies were achieved within 5 min of operation. Three times of repetition in CP resulted in higher removal efficiencies for COD, SS and colour up to 74%, 99% and 94% respectively, in which Al2(SO4)3 was used as the coagulant. Removal efficiencies of various water quality parameters in a continuously operated reactor were similar to those of the batch experiments. Biodegradable ratios (BOD5/COD) increased up to 65% after the application of CP.     

Cost-effective upgrading of a biological wastewater treatment plant by using lamella separators with bypass operation.

Based on a comprehensive cost analysis for the expansion of the Finnentrop WWTP, integration of lamella separators in the biological treatment stage was given priority as optimal solution to increase the solids concentration. The overall expansion project included the reconstruction of the former primary clarifier into a primary settling tank with short retention times and the use of the remaining volume for pre-denitrification. Four lamella separators were positioned in the existing carousel-type activated sludge tank. With the lamella assemblies ensuring it was possible to continue operation of the existing secondary settling tanks. To control an adequate solids concentration in the activated sludge tank and to avoid any overloading of the secondary settling tank, a newly developed bypass strategy was applied. With a controlled mixing of direct effluent from the lamella separators and the contents of the activated sludge tank, the solids concentration of the influent to the secondary settling tank could be maintained at a value of 2.2 kg/m(3). The lamella separator concept did not account for any significant changes in the sludge characteristics, and the overall elimination of nutrients and organic carbon was found to be excellent upon optimisation of the operational lamella strategy.     

Integration of chemical and biological oxidation in a SBBR for tannery wastewater treatment.

This paper reports the results of an investigation aimed at evaluating the laboratory-scale performance of an innovative process for treating tannery wastewater. In this process, biological degradation, carried out in a sequencing batch biofilm reactor (SBBR), is combined with chemical oxidation by ozone. Tannery wastewater treatment was carried out, at laboratory scale, on a real primary effluent coming from a centralised plant treating wastewater produced by a large tannery district in Northern Italy. SBBR performance both without and with ozonation, was assessed with very satisfactory results. In particular, in the latter instance the recorded COD, TKN and TSS average removals, (96%), (92%) and (98%) respectively, allowed the maximum allowable concentration values fixed by the Italian regulation in force to be achieved without any additional polishing step. During the investigation biofilm properties (biofilm concentration and biofilm density) and flow dynamics aspects (head loss, shear stress, bed porosity) were also studied. A major feature of the process is that, with or without ozonation, it was characterised by very low specific sludge production (0.05 kgVSS/kgCODremoved) and high biofilm density (i.e. 87-122 gVSS/Lsludge) both contributing to a rather high biofilm concentration (i.e. 31-44 gTSS/Lfilter).     

Setting-up a cost recovery system for the largest wastewater treatment plant in South-East Asia.

A tariff system has been set up for the largest wastewater treatment plant in South-East Asia, the Samut Prakarn Wastewater Treatment Plant south of Bangkok, which is currently under completion. Fully functional the plant will have a design capacity for 500,000 m3 per day and will service a combined residential and industrial area with approximately 600,000 residents and 2,300 factories. The tariff system, which includes a tariff model, is based on water consumption and BOD load. As background for setting the tariffs a comprehensive monitoring system including an industrial permitting system has been developed. The paper presents the background and rationale for setting up the system as well as the objective, scope and content of the tariff system and the industrial permit system. Further, the feasibility of introducing cost recovery systems, which is widely accepted in developing economies on the conceptual level and to some extent implemented at the legal and regulatory level, but has yet to be implemented at large, is discussed.     

Selection of an ultraviolet disinfection system for a municipal wastewater treatment plant.

As part of an expansion to an average flow of 45.9 million gallons per day (174 mld), the Ypsilanti Community Utilities Authority wastewater treatment plant in the State of Michigan, USA, elected to install ultraviolet disinfection as a replacement for the existing chlorination process. This paper presents a unique methodology used in selecting the best system based on not only the life cycle costs, and O & M considerations but also the participation of the stakeholders. The Team members consisted of representatives of all departments at the Authority, and these Team members made the decision. The Team evaluated all criteria in the office, which was followed by verification at selected sites with similar types of equipment. The selected equipment then was pilot tested for validation of the dose-kill relationship under normal operation and also under reduced irradiation conditions. A low-pressure, high intensity system was selected, based on life-cycle cost, reliability, safety, and ease of operation. This paper describes the unique methodologies used in making that decision. The full-scale system is scheduled for start-up in Spring 2003.     

Increasing the capacity of an extended nutrient removal plant by using different techniques

A comprehensive investigation which included full scale tests was initiated towards the late 1980:s with the primary aim to find an appropriate upgrading technology for the Klagshamn wastewater treatment plant in Malmö, Sweden. The finally selected strategy enabled that a concentration of less than 8 mg N/1 could be reached in the secondary effluent without having to extend either the primary or secondary treatment step at the actual load on the plant In order to comply with a future stringent phosphorus standard however, a tertiary filtration plant has to be built In future, it has to be anticipated that the load on the plant may be doubled due to the fact that a bridge between Malmo and Copenhagen is being built As a consequence, it was important to continue the upgrading work by estimating the ultimate plant capacity and to look for measures to increase the capacity if necessary. By optimising the plant operation, it seems possible to reach an effluent nitrogen concentration of less than 12 mg/l at a load corresponding to the future design load. The suggested approach implies that the plant has to be operated on the margin and as a consequence the possibility to include a denitrification step as part of the filtration plant was also investigated. As a result it was decided to build a separate denitrification step at the same time as the filtration plant was built.     

Model-based evaluation of nitrogen removal in a tannery wastewater treatment plant.

Computer modelling has been used in the last 15 years as a powerful tool for understanding the behaviour of activated sludge wastewater treatment systems. However, computer models are mainly applied for domestic wastewater treatment plants (WWTPs). Application of these types of models to industrial wastewater treatment plants requires a different model structure and an accurate estimation of the kinetics and stoichiometry of the model parameters, which may be different from the ones used for domestic wastewater. Most of these parameters are strongly dependent on the wastewater composition. In this study a modified version of the activated sludge model No. 1 (ASM 1) was used to describe a tannery WWTP. Several biological tests and complementary physical-chemical analyses were performed to characterise the wastewater and sludge composition in the context of activated sludge modelling. The proposed model was calibrated under steady-state conditions and validated under dynamic flow conditions. The model was successfully used to obtain insight into the existing plant performance, possible extension and options for process optimisation. The model illustrated the potential capacity of the plant to achieve full denitrification and to handle a higher hydraulic load. Moreover, the use of a mathematical model as an effective tool in decision making was demonstrated.     

Strategy for olive mill wastewater treatment and reuse with a sewage plant in an arid region.

This study was conducted to evaluate the treatability of OMW (olive mill wastewater) with sewage and sewage sludge, which could supplement nutrients and microbes required for OMW treatment and reduce its possible toxicity. The amount of OMW added to an aeration tank was based on the loading difference between the designed and actual COD loads, while the amount added to anaerobic digestion for energy recovery was determined by CH4 production. The COD removal efficiencies were 70-85% for both systems. Compost of OMW with dried sewage sludge also showed a similar temperature profile without OMW addition. This strongly suggested that OMW can be treated at a sewage plant without pretreatment and the treated effluent can be reused in irrigation for an arid region.     

Integrated modelling of sewer system and wastewater treatment plant for investigating the impacts of chemical dosing in sewers

Chemicals are often dosed to control the production and accumulation of hydrogen sulfide in sewers. The biological and/or chemical actions of these chemicals have profound impacts on the composition of wastewater entering a WWTP, thereby affecting its performance. In this paper, an integrated modelling methodology for simultaneously investigating the effects of dosing of chemicals in sewer network and N and P removal at the downstream WWTP is reported. The sewer system is modelled using a sewer model (SeweX), and the WWTP is modelled using ASM2d model with some modifications. The importance of integrated modelling in sewer management is also demonstrated.     

Increasing the capacity of hydroelectric plant units in the Karelian power system

Conclusion Determining the capacity reserve of hydraulic turbines and subsequently increasing the capacity of generators constitutes one of the directions for utilizing the internal reserves of hydroelectric plants and more effectively using hydropower resources. Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 1, p. 54, January, 1977.     

Use of on-line data to evaluate the activity in the biological stage at a wastewater treatment plant

Today many WWTPs are equipped with different on-line instruments for automatic and manual control of the process. The use of computerised systems for data acquisition gives us new possibilities to evaluate collected data. This study shows the possibilities and potentials in using standard equipment, simple calculations and the biological stage as a measuring cell for activity determinations.Evaluation of data from Henriksdal and Bromma WWTP give some examples from the biological stage where activity can be calculated on-line. The calculation of Oxygen Uptake Rates, OUR, can be used in several ways: a) Estimation of the overall activity in the aerated part of biological stage, b) Calculations of the load of oxygen consuming substanses on the aerated basin, c) Calculation of nitrification rate, d) Estimation of necessary aerated volume, e) Rapid detection of inhibition of the nitrification (and other oxygen consuming reactions). One advantage with these calculations is the fast response to changes.     

Mosquito development and biological control in a macrophyte-based wastewater treatment plant.

A one-year study of the proliferation of mosquito in a Pistia stratiotes-based waste stabilization ponds in Cameroon revealed that Mansonia and Culex were the main breeding genera with about 55% and 42% of the total imagoes respectively. Though the ponds represent a favorable breeding ground for mosquitoes, only 0.02% of captured imagoes was Anopheles gambiae, suggesting that this wastewater treatment plant does not significantly contribute to the development of the malaria vector in the area. Gambusia sp. introduced to control mosquito population in the ponds acclimatized relatively well in most of the ponds (B3-B7) and their feeding rate without any diet ranged from 15.0 to 50.2 larvae/day for a single fish.     

微孔曝气器充氧性能变化对污水处理厂能耗的影响

以北京小红门污水处理厂的新、旧刚玉盘式微孔曝气器为例,进行曝气充氧性能的试验研究,并分析了更换曝气器对污水处理厂能耗的影响。结果表明:经过长期使用的曝气器充氧性能下降较大,氧总转移系数、氧的利用效率和动力效率分别下降了57%、58%和59%。旧微孔曝气器氧的利用效率为8.9%～14.1%,略高于中大气泡曝气器的性能参数,但由于微孔曝气器具有较大的阻力损失,使旧微孔曝气器的动力效率为1.5～2.1kgO2/(kW.h),低于中大气泡曝气器的性能参数。更换小红门全厂1/4的微孔曝气器后,鼓风机单耗降低21%,全厂能耗降低12%。因此,当微孔曝气器的充氧性能下降较大时,更换新的曝气器具有较高的节能和经济效益。     

成都市乡镇污水处理厂工艺方案探讨与选择

乡镇污水处理厂地理位置分散,经济条件较差,进水水质和水量波动较大,直接套用大型污水处理厂的处理工艺难以满足要求。介绍了几种适用于小城镇的污水处理工艺,并对其进行适用特点和经济性分析,在此基础上提出成都市乡镇污水处理厂的工艺方案选择建议。