Minimising the risk on phosphorus limitation; an optimised coagulant dosage system

In the near future the WWTP Horstermeer will be confronted with more stringent requirements. Important factor in this respect is the European Water Framework Directive 2000/60/EC. Within the WFD approach the focus is more and more on low nitrogen (<2.2 mg N-total/L) and phosphorus concentrations (<0.15 mg P-total/L) in WWTP effluent. Therefore, research has been initiated at the Horstermeer WWTP to investigate the possibilities of simultaneous nutrient removal with filtration techniques. After nitrite accumulation, caused by phosphorus limitation, was measured in the filtrate water of the 1-STEP filter, research has started. The objective of this research is to minimise the risk on the inhibition of denitrification by phosphorus limitation and to decrease the dosage of coagulant. Therefore a new coagulant dosage system is developed. The back-ground of the coagulant dosage system, the results and cost savings are discussed in this article. When the PO4-P/NOx-N ratio in the WWTP effluent becomes below 0.06 mg/mg phosphorus limitation may occur. The results for phosphorus and nitrogen removal are equal or improved compared to the yearly average of 2008. The results show a more stable removal process and a reduction of the coagulant dosage for the coagulant dosage system of 11% when compared to a continuous dosage ratio of MeP 4 mol/mol.     

Nutrient removal process selection for planning and design of large wastewater treatment plant upgrade needs.

A protocol to select nutrient removal technologies that can achieve low nutrient effluents (total nitrogen (TN) < 5 mg/L and total phosphorus (TP) < 0.5 mg/L) was developed for different wastewater treatment plant (WWTP) sizes based on the research conducted during a Water Environment Research Foundation funded project. The adaptable protocol includes technology and cost assessment of feasible (pre-screened) nutrient removal technologies that are being successfully implemented at full scale. The information collected from the full scale nutrient removal plants to develop this protocol includes design, operational, performance, and cost data through a direct survey of plants, and published data. The protocol includes a "technology threshold" approach consisting of Tier I (TN < 5.0 mg/L; TP < 0.5 mg/L) and Tier II (TN < 3.0 mg/L; TP < 0.1 mg/L) effluent nutrient levels for different plant sizes. A very large WWTP (1,250,000 m(3)/day flow) in Chicago, Illinois, USA adapted this protocol for master planning and design of future nutrient removal facilities based on plant and site specific criteria.     

潜流湿地对微污染水体中氮磷去除效果的中试研究

以南京水利科学研究院铁心桥试验基地内象目湖微污染水体为对象,研究总氮大于1.0 m3/(m2·d)的高水力负荷条件下,鹅卵石、陶粒、砾石、钢渣、蛭石、碎石和砂子等多种基质和再力花、芦苇、美人蕉及菖蒲等水生植物组合条件下的垂直流湿地和水平潜流湿地对氮磷的去除效果。试验结果表明:进水总氮浓度在0.793~2.662 mg/L时,种植菖蒲,填料从上到下分别为鹅卵石、碎石、粗砂和细砂的垂直潜流湿地单元(20单元)出水总氮平均浓度最低,为0.905 mg/L;总氮、氨氮和硝态氮平均去除率最高,达80.89%,43.06%和46.32%;总氮浓度从Ⅳ类水体提升至Ⅲ类。进水TP浓度在0.035~1.003 mg/L时,20单元总磷平均去除率最高,为30.59%,价格相对便宜的碎石对磷素的去除效果较好。种植菖蒲及填料组合为鹅卵石、碎石、粗砂和细砂的人工湿地处理单元可以应用于饮用水源地原水等微污染水强化处理。     

MBR工艺处理城镇污水处理厂污泥水中试研究

将平板膜组件与传统脱氮除磷工艺相结合,构建了膜生物反应器强化生物脱氮除磷中试系统,并用于处理城镇污水处理厂的污泥系统废水。结果表明,出水CODCr、BOD5、NH3—N、TN和TP的平均浓度分别为70.8 mg/L、8.7 mg/L、15.1 mg/L、29.7 mg/L和0.38 mg/L,达到或接近了《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级标准。     

Use of agro-food wastewaters for the optimisation of the denitrification process.

The aim of this work was to study the feasibility of the denitrification process enhancement, in the Ciudad Real (Spain) WWTP, by dosing agro-food wastewaters generated nearby the city. The studied agro-food wastewaters were characterised by a high COD and low nutrients concentration. The denitrification rates with these wastewaters were lower than those obtained either with acetate or urban sewage, however the dose of agro-food wastewaters raised significantly the denitrification capacity in the WWTP because of the significant increase of easily biodegradable substrates in the wastewater. From the laboratory NUR batch test it was observed that the best agro-food wastewater to enhance the denitrification process was that coming from tomato processing, which presented an average denitrification rate of 1.9 mg NOx-N/(g VSS.h) and an average denitrification yield of 0.2 mg NOx-N/mg COD. The viability of the use of tomato processing wastewater was checked in a pilot plant optimised for urban sewage treatment with biological nutrient removal. The optimum dose, 5.9 mg COD/mg NOx-N, was applied and 99% of the nitrate was removed from the wastewater without influencing negatively either the COD or P effluent concentrations.     

Behaviour of heavy metals during tertiary bio-filtration.

More stringent water quality parameters in the Annex of the Water Framework Directive 2000/60/EC led to the introduction of "Maximum Tolerable Risk concentrations" (MTR-values) in the national legislation in The Netherlands (Vierde Nota Waterhuishouding). The MTR-values give limitations for the concentrations of e.g. heavy metals (HM's) but also for nutrients: Ntot < 2.2 mg/l, Ptot <0.15 mg/l. Investigations of HM removal during denitrifying flocculation filtration are conducted on the effluent of a typical modern Dutch WWTP. Because of low concentrations of HM's in the feed water, a cocktail of copper, nickel and zinc chloride (approximately equal 150-200 microg/l) is dosed before filtration. Preliminary jar tests and filtration tests with media filtration in pilot-scale and lab-scale are conducted. The results show high removal of nickel and zinc during jar tests with dosing of powdered activated carbon. During filtration tests at pilot-scale the bounded fraction of copper and zinc is highly removed. All three HM's are removed in the lab-scale activated carbon filter. After dosing, nickel is found mainly in the dissolved form, but it is removed in the lab-scale activated carbon filter. The removal of HM's via adsorption subsequently leads to a discussion on the toxicity of HM's and their bio-availability.     

Dissolved oxygen, COD, nitrogen and phosphorus profiles in a continuous sand filter used for WWTP effluent reclamation

Continuous sand filtration (CSF) offers interesting potential for the extensive treatment of wastewater treatment plant (WWTP) effluents for water reclamation and/or restrictive discharge. Research on concentration profiles over the height of the CSF shows that most bacteriological conversions are restricted to the lower part of the filter bed. Dissolved oxygen (DO) rapidly decreases to below 1 mg/L in the first 0.4 m of the filter bed, applying hydraulic velocities of 12.9 ～ 14.9 m/h and 10 ～ 20 mm/min sand velocities, independent of the methanol dosage. The DO decrease agrees with the observed decrease in chemical oxygen demand (COD). At the given operational conditions, NO(x)-N and N-total removal is dedicated to the first 0.9 m of the filter bed. Results show that by optimising the CSF operational conditions the very restrictive effluent N and P values of 2.2 and 0.15 mg/L, respectively, as described in the European Water Framework Directive, can be met.     

Removal of nitrogen, phosphorus and other priority (hazardous) substances from WWTP effluent.

More stringent effluent criteria will be required in the near future for the so-called priority substances listed in the Annex of the European Water Framework Directive (WFD) 2000/60/EC. This includes heavy metals, volatile and semi-volatile organic substances, pesticides and polychlorinated biphenyls. The Fraunhofer Institute suggested FHI values for these substances in water. National Dutch legislation, the Vierde Nota WaterHuishouding (NWH) introduced in 1998 'maximum tolerable risk concentrations' (MTR). These include requirements for nutrients: P(tot) < 0.15 mg/l and N(tot) < 2.2 mg/l. The MTR values are being used until the FHI values become effective. Investigation into possible effluent polishing techniques is required in order to reach these objectives. During pilot research with tertiary denitrifying multi-media and biological activated carbon filtration at the WWTP Utrecht in The Netherlands, simultaneous nutrient removal to MTR quality was observed. Furthermore, simultaneous removal of heavy metals, 17beta-estradiol, bisphenol A and nonylphenols to extreme low concentrations by denitrifying activated carbon filtrated is achieved.     

污泥碱解发酵液用于生活污水脱氮 除磷的效果研究

为了减轻水体富营养化程度,提高污水的脱氮除磷效果,并解决污泥减量化和资源化问题,本研究将碱预处理的污泥进行厌氧发酵产酸,并将发酵液作为污水脱氮除磷的外加碳源。研究结果表明：投加污泥发酵液后,出水氨氮浓度为0.3~0.5 mg/L,总磷浓度为0.5 mg/L,与未投加污泥发酵液相比分别降低了1.7~2.3 mg/L和3~4 mg/L。     

Effluent treatment by multi-media filtration, microfiltration and ultrafiltration: results of a pilot investigation at WWTP Hoek van Holland.

Upgrading of wastewater treatment plant (WWTP) effluent as a part of the Dutch governmental policy to close the water cycle has increasing interest now. The Water Board Hoogheemraadschap van Delfland together with the project team of Witteveen + Bos Consulting Engineers, Delft University of Technology and Rossmark water treatment investigated the reuse possibilities of WWTP effluent in the region of Delfland. Therefore pilot research was carried out at WWTP Hoek van Holland applying different filtration techniques: multi-media filtration, micro- and ultrafiltration. The results show stable process performances of the different filtration techniques when proper pre-treatment was applied. For microfiltration the filtration characteristics were strongly influenced by particles which were not retained in the multi-media filter. For ultrafiltration the filtration characteristics were strongly influenced by organic components < 0.2 microm. The upgraded WWTP effluent could not be used directly as process water or for agriculture purposes, due to high concentrations of COD and salts in the WWTP effluent and filtrates. However WWTP effluent or floc filtrate could be applied directly as water for the washing of sea-sand.     

Treatment of slaughterhouse plant wastewater by using a membrane bioreactor

The use of a membrane bioreactor (MBR) for removal of organic substances and nutrients from slaughterhouse plant wastewater was investigated. The chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations of slaughterhouse wastewater were found to be approximately 571 mg O2/L, 102.5 mg/L, and 16.25 mg PO4-P/L, respectively. A submerged type membrane was used in the bioreactor. The removal efficiencies for COD, total organic carbon (TOC), TP and TN were found to be 97, 96, 65, 44% respectively. The COD value of wastewater was decreased to 16 mg/L (COD discharge standard for slaughterhouse plant wastewaters is 160 mg/L). TOC was decreased to 9 mg/L (TOC discharge standard for slaughterhouse plant wastewaters is 20 mg/L). Ammonium, and nitrate nitrogen concentrations of treated effluent were 0.100 mg NH4-N/L, and 80.521 mg NO3-N/L, respectively. Slaughterhouse wastewater was successfully treated with the MBR process.     

Impacts of water quality variation and rainfall runoff on Jinpen Reservoir,in Northwest China

The seasonal variation characteristics of the water quality of the Jinpen Reservoir and the impacts of rainfall runoff on the reservoir were investigated. Water quality monitoring results indicated that, during the stable stratification period, the maximum concentrations of total nitrogen, total phosphorus, ammonia nitrogen, total organic carbon, iron ion, and manganese ion in the water at the reservoir bottom on September6 reached 2.5 mg/L, 0.12 mg/L, 0.58 mg/L, 3.2 mg/L, 0.97 mg/L, and 0.32 mg/L, respectively. Only heavy storm runoff can affect the main reservoir and cause the water quality to seriously deteriorate. During heavy storms, the stratification of the reservoir was destroyed, and the reservoir water quality consequently deteriorated due to the high-turbidity particulate phosphorus and organic matter in runoff. The turbidity and concentrations of total phosphorus and total organic carbon in the main reservoir increased to 265 NTU, 0.224 mg/L, and 3.9 mg/L, respectively.Potential methods of dealing with the water problems in the Jinpen Reservoir are proposed. Both in stratification and in storm periods, the use of measures such as adjusting intake height, storing clean water, and releasing turbid flow can be helpful to safeguarding the quality of water supplied to the water treatment plants.     

WEF/WERF study of BNR plants achieving very low N and P limits: evaluation of technology performance and process reliability

The Water Environment Research Foundation (WERF) funded a two-year comprehensive study of nutrient removal plants designed and operated to meet very low effluent total nitrogen (TN) and total phosphorus (TP) concentrations. WERF worked with the Water Environment Federation (WEF) to solicit participation of volunteers and provide a forum for information exchange at workshops at its annual conferences. Both existing and new technologies are being adapted to meet requirements that are as low as 3.0 mg/L TN and 0.1 mg/L TP, and there is a need to define their capabilities and reliabilities in the real world situation of wastewater treatment plants. A concern over very low daily permits for ammonia caused the work to be extended to include nitrification reliability. This effort focused on maximizing what can be learned from existing technologies in order to provide a database that will inform key decision makers about proper choices for both technologies and rationale bases for statistical permit writing. To this end, managers of 22 plants, 10 achieving low effluent TP, nine achieving low effluent TN, and three achieving low effluent NH(3)-N, provided three years of operational data that were analyzed using a consistent statistical approach. Technology Performance Statistics (TPSs) were developed as three separate values representing the ideal, median, and reliably achievable performance. Technological conclusions can be drawn from the study in terms of what can be learned by comparing the different nutrient removal and nitrification processes employed at these 22 plants.     

SHARON process evaluated for improved wastewater treatment plant nitrogen effluent quality.

New stricter nitrogen effluent standards and increasing influent loads require existing wastewater treatment plans (WWTPs) to extend or optimize. At WWTPs with limited aeration capacity, limited denitrification capacity or shortage of aerobic sludge age, implementation of SHARON to improve nitrogen effluent quality can be a solution. SHARON is a compact, sustainable and cost-effective biological process for treatment of nitrogen-rich rejection waters. At WWTP Rotterdam-Dokhaven and WWTP Utrecht a SHARON has been in operation for several years. For both WWTPs the effect of SHARON on the nitrogen effluent quality has been evaluated. WWTP Rotterdam-Dokhaven has limited aeration capacity. By implementation of SHARON, the ammonia load of the effluent was reduced by 50%. WWTP Utrecht had limited denitrification capacity. The implementation of SHARON improved the effluent nitrate load by 40%. The overall TN removal efficiency increased from 65% to over 75% and strict nitrogen effluents standards (TN = 10 mg N/l) could be reached. Through modelling and supported by full scale practice it has been shown that by implementation of SHARON in combination with enhanced influent pre-treatment, the aerobic sludge age can be extended to maintain total nitrogen removal at lower temperatures.     

3D Eutrophication Modeling of Hamilton Harbour: Analysis of Remedial Options

The Water Quality Analysis Simulation Program (WASP) was employed to create a threedimensional eutrophication model for Hamilton Harbour. Calibration of the model was performed using 1991 field data. Four remedial options, namely improvements to the waste water treatment plants (WWTPs), the combined sewer overflows (CSOs), industrial discharges, and removal of WWTP, CSO, and industrial discharges were examined. The model simulated well the response of the harbor under various loading conditions. Improvements in the harbor's water quality were found to range from minor in the case of CSO improvements to significant in the case of WWTP improvements. Specifically, the chlorophyll a, total phosphorus, and ammonia nitrogen concentrations were reduced by as much as 2% in the case of CSO improvements, between 4 and 14% for the industrial loading improvements, and between 24 and 50% for the WWTP improvements case.     

Full scale implementation of the nutrient limited BAS process at S?dra Cell V?r?.

A combination of the suspended carrier biofilm process and the activated sludge process (biofilm-activated sludge--BAS) has been shown to be very successful for the treatment of different types of pulp and paper mill effluents. The robust biofilm pre-treatment in combination with activated sludge results in a stable, compact and highly efficient process. Recent findings have shown that nutrient limited operation of the biofilm process greatly improves the sludge characteristics in the following activated sludge stage, while minimising sludge production and effluent discharge of nutrients. The nutrient limited BAS process was implemented at full scale at the S?dra Cell V?r? kraft mill and taken into operation in July 2002. After start-up and optimisation over about 5 months, the process meets all effluent discharge limits. The removal of COD is close to 70% and the removal of EDTA greater than 90%. Typical effluent concentrations of suspended solids and nutrients during stable operations have been 20-30 mg/L TSS, 0.3-0.5 mg/L phosphorus and 3-5 mg/L nitrogen. The sludge production was 0.09 kgSS/kg COD removed and the sludge volume index was 50-100 mL/g.     

Comparison of the nutrient removal efficiency of onsite wastewater treatments systems: applications of conventional sand filters and sequencing batch reactors (SBR).

When domestic wastewater was treated with different onsite applications of buried sand filters and sequencing batch reactors, good organic matter removal was common and effluent BOD7 concentrations from 5 to 20 mg/l were easily achievable. For total nitrogen, effluent concentrations were usually between 20 and 80 mg/l. Good phosphorus removal, even using special adsorption or precipitation materials, was difficult to achieve and large variations occurred. The median effluent concentration of total phosphorus in the most successful sand filter application was less than 0.1 mg/l and other sand filters and SBRs had the median concentrations varying from 1.7 to 6.7 mg/l. These results are based on one year in situ monitoring of 2 conventional buried sand filters, 6 sand filter applications with special phosphorus adsorbing media within the filter bed, 5 sand filters with separate tertiary phosphorus filtration and 11 small SBRs of three different types. The study was carried out in southern Finland during 2003-05. The whole project included monitoring of more than 60 plants of 20 different treatment types or methods, used in normal conditions to treat domestic wastewater. Evaluation of the different systems was made by comparing the measured effluent concentrations. In addition the effluent concentrations were compared to the discharge limits calculated according to the new Finnish regulation.     

数学模型在污水处理厂优化控制过程中的应用

通过小试结合模拟计算,分析了某污水处理厂现有运行存在的不足.试验表明,内回流比对提高脱氮率的作用是有限制条件的;对于溶解氧的控制,要根据系统硝化反应的需要来确定;缺氧区/总体积的比例是影响脱氮效果的一个关键因素,在保证硝化不受影响的前提下,增大缺氧区使反硝化进行得更充分,有助于提高系统的脱氮能力.通过模拟计算,对其工艺参数进行了优化组合,在不改变池容、不增加其他处理设施的情况下提出了优化方案,确定其最佳工艺控制参数为:缺氧区/总体积的比例为0.45,混合液内回流比为200%,好氧区溶解氧2 mg/L.调整后的出水总氮为21.77 mg/L,去除率较改造前提高了4%,出水氨氮浓度为1.16 mg/L,去除率提高了7.2 %.     

Outcomes of a 2-year investigation on enhanced biological nutrients removal and trace organics elimination in membrane bioreactor (MBR).

Two configurations of membrane bioreactors were identified to achieve enhanced biological phosphorus and nitrogen removal, and assessed over more than two years with two parallel pilot plants of 2m3 each. Both configurations included an anaerobic zone ahead of the biological reactor, and differed by the position of the anoxic zone: standard pre-denitrification, or post-denitrification without dosing of carbon source. Both configurations achieved improved phosphorus removal. The goal of 50 microgP/L in the effluent could be consistently achieved with two types of municipal wastewater, the second site requiring a low dose of ferric salt ferric salt < 3 mgFe/L. The full potential of biological phosphorus removal could be demonstrated during phosphate spiking trials, where up to 1 mg of phosphorus was biologically eliminated for 10 mg BOD5 in the influent. The post-denitrification configuration enabled a very good elimination of nitrogen. Daily nitrate concentration as low as 1 mgN/L could be monitored in the effluent in some periods. The denitrification rates, greater than those expected for endogenous denitrification, could be accounted for by the use of the glycogene pool, internally stored by the denitrifying microorganisms in the anaerobic zone. Pharmaceuticals residues and steroids were regularly monitored on the two parallel MBR pilot plants during the length of the trials, and compared with the performance of the Berlin-Ruhleben WWTP. Although some compounds such as carbamazepine were persistent through all the systems, most of the compounds could be better removed by the MBR plants. The influence of temperature, sludge age and compound concentration could be shown, as well as the significance of biological mechanisms in the removal of trace organic compounds.     

太阳能曝气人工垂直潜流湿地去除生活污水氮磷的试验研究

利用芦苇和砾石构建太阳能曝气人工垂直潜流湿地处理生活污水。设定水力负荷400 mm/d,气水比10∶1,当进水氨氮(NH₄-N)、总氮(TN)、溶解性反应磷(SRP)和总磷(TP)平均浓度为5.14,7.56,0.40,0.53 mg/L时,引入太阳能曝气后,各自的平均去除率分别提高24.8%,9.4%,15.7%和11.5%。随着气温下降和进水浓度降低,湿地微生物脱氮除磷能力下降,曝气对改善生活污水氮磷去除作用不显著。对试验系统而言,太阳能曝气湿地基本建设费用是无曝气湿地的2.85倍;但以20 a运行为基础折算出的污水处理费比无曝气湿地仅高0.02元/m³。综上,从污染去除性能和污水长期处理费用来看,太阳能曝气湿地在生活污水处理方面具有较好的技术经济优势。