A Pilot Study on Performance of a Membrane Bio‐Reactor in Treating Fresh Water Sewage and Saline Sewage in Hong Kong

Abstract

The results of two pilot studies of an immersed membrane bioreactor (MBR) treating fresh water and saline sewage in Hong Kong are presented. The objectives were to demonstrate suitability of the MBR technology to the treatment of Hong Kong sewage and its ability to achieve total nitrogen removal effectively. When operated in nitrification/denitrification mode, the MBR was able to achieve 98% BOD removal, 90–93% COD removal and 82–84% total nitrogen removal with a HRT of 6.8 hours and 300% internal flow recirculation. Very low effluent NH₄ ⁺‐N levels were observed throughout the study suggesting complete nitrification. The MBR was able to achieve full denitrification utilizing organic matter in the raw sewage as a carbon source. The nitrogen removal capacity of the MBR was limited by nitrogen loadings rather than the biological activity in the reactor. The results did not indicate any significant differences in treatment performances with fresh water and saline sewage except that a higher frequency of membrane cleaning was required for the latter.     

潜流人工湿地对农村生活污水处理特性试验研究

采用潜流人工湿地处理农村生活污水,考察了该工艺对COD、BOD5、NH3-N、TN和TP的去除效果。结果表明,湿地对COD、BOD5、NH3-N、TN和TP的去除效果较好,平均去除率分别达到87.4%、83.5%、63.8%、57.9%和90.1%,出水COD为11.2～23.3 mg.L-1,出水BOD5为6.7～11.3 mg.L-1,出水NH3-N、TN、TP的质量浓度分别为10.3～16.1、18.8～23.2、小于1.0 mg.L-1,出水水质优于GB 5084-2005要求。植物种植状况、温度变化及进水污染物含量等因素对湿地处理效率有较大影响,总体上来讲,温度大于20℃、植物种植密度越大、进水污染物含量越低处理效果越好。     

Removal of nitrogen from wastewater for reusing to boiler feed-water by an anaerobic/aerobic/membrane bioreactor

The innovative process anaerobic/aerobic/membrane bioreactor (A/O/MBR) was developed to enhance pre-denitrification without the energy consumption of the recirculation pump for reusing wastewater to boiler feed-water. The performance of this bioreactor was investigated. Firstly, the septic tank wastewater with low ratio of COD/TN was disposed by a dynamic membrane bioreactor (DMBR). It was found that, although the high concentration of NO₂⁻–N in the effluent implied the potential ability of DMBR to realize shortcut nitrification and denitrification, the effluent of single DMBR was difficult to reach the criteria of reusing to boiler feed-water. Then, the process A/O/DMBR in disposing the septic tank wastewater was studied. The results indicated that this process not only accomplished the removal of 91.5% COD, 90.3% NH₄⁺–N and 60.2% TN, but also successfully realized pre-denitrification without additional recirculation pump. At last, based on the A/O/DMBR, a pilot plant A/O/MBR was built to dispose the municipal raw sewage. In the stable operation period, the average removal efficiencies for COD, NH₄⁺–N, TP and turbidity reached 90%, 95%, 70% and 99%, respectively. During the tested HRT run of 9.0 h, the effluent of COD, NH₄⁺–N, TP and turbidity was about 10 mg/L, 3 mg/L, below 1 mg/L and 1.2 NTU, respectively, which reached the criteria of the boiler feed-water in China.     

Full-scale study on dynamic state membrane bio-reactor with modified intermittent aeration

In order to evaluate the performance of a newly developed dynamic state membrane bio-reactor (MBR) with MIA, a full-scale plant with the capacity of 210 m³/d was operated for treating sewage. Due to the MIA, the effect of residual oxygen could be completely removed during the non-aeration period and recycle ratio could be reduced to 1 recycle-to-influent ratio. Even though the plant was operated in winter season, stable performance could be achieved (BOD, CODcr, SS, TN, TP and E. coli removal efficiency; 98.2, 95.2, 99.8, 72.7, 71.4 and 99.9%, respectively). Therefore newly developed dynamic state MBR with the MIA can be one of the useful biological nutrient removal (BNR) processes for stable nutrient removal.     

淹没式MBR处理啤酒废水的净化效能研究

在投加营养物质,保持COD:TN:TP=100:5:1的条件下,淹没式MBR对啤酒废水中的COD、NH 4-N有着较好的去除效果,系统稳定时COD与NH 4-N的平均去除率均在90%以上,而且MBR工艺对进水有机负荷的冲击具有较强的短时适应能力,当COD污泥负荷由0.27g/g·d突然增加至0.54g/g·d时,出水COD浓度未出现明显的波动。通过GC/MS分析得出,膜组件出水中剩余的有机物主要为高分子量的烷烃类,膜组件对于保证系统的最终出水水质起到了关键的作用。     

Application of ultrafiltration membranes for removal of humic acid from drinking water

Humic acids are primarily a result of the microbiological degradation of surrounding vegetation and animal decay and enter surface waters through rain water run-off from the surrounding land. This often gives rise to large seasonal variations, high concentrations in the wet season and lower concentrations in the dry season. Alone humic acid is just a colour problem but when present in conventional treatment processes like chlorination, carcinogenic by-products like trihalomethane and haloacetic acid are formed. This, in addition to the demand for clean potable drinking water, has sparked extensive research into alternative processes for the production of drinking water from various natural/industrial sources. One of the major areas of focus in these studies is the use of membranes in microfiltration, ultrafiltration and nanofiltration. In this report the humic acid removal efficiency of ultrafiltration membranes with 3 kDa, 5 kDa and 10 kDa MWCO is examined. The membranes were made of regenerated cellulose and were in the form of cassette providing a 0.1 m² surface area. At first distilled and deionised water, known as milliQ water, was used as the background feed solution to which humic acid powder was added. It was found that all three membranes removed humic acid with an efficiency of approx. 90% and were capable of reducing initial concentrations of 15mg/L to below the New Zealand regulatory limit of 1.17 mg/L. The permeate flux at a transmembrane pressure of 2.1 bar was approx. 20 l/m²/h (LMH) and 40 LMH, respectively through the membranes with MWCO 3 kDa and 5 kDa. These membranes experienced significant surface fouling resulting in retentate flow rates as low as 11 litres per hour after just four runs compared to the recommended 60–90 l/h. Cleaning with 0.1 M NaOH slightly improved the retentate flow rate, but well below those obtained with fresh membranes. The 10 kDa membrane provided high retentate flow rates which evidently minimised fouling by providing a good sweeping action across the membrane surface while maintaining humic acid removal below the regulatory 1.17 mg/L level. The permeate flux through this membrane was initially high (140–180 LMH) and reduced to approx. 100 LMH after 10–12 min of operation. Increasing the initial humic acid feed concentration from 10 mg/L to 50 mg/L did not significantly decrease humic acid removal efficiency although the retentate flow rate was lower at higher concentrations. Finally the tap water was tested as the background solution and treated for the removal of humic acid. The presence of ions and other impurities in the tap water had little effect on humic acid removal. However, the permeate flux through 10 kDa membrane decreased from 100 LMH for milliQ water to 60 LMH for tap water after 20 min of operation.     

新型海藻式膜生物反应器处理印染废水的应用研究

针对印染废水成分复杂、色度大、浓度高且生物难降解物质多等特点,采用了混凝沉淀法对印染废水进行预处理,然后采用新型海藻式膜生物反应器(MBR)对印染废水进行活性污泥法处理试验研究.通过对COD、BOD、NH_3-N、TN、TP、色度、浊度等水质指标连续进行测定、分析与处理,考察MBR对印染废水的降解效果,并观察系统运行情况和膜组件污染状况.试验结果表明,海藻式MBR对印染废水的处理效果良好,出水浊度低于0.3 NTU,对COD、BOD、色度、NH_3-N、TN的去除率分别可达90%、94%、91.4%、87.8%、86.4%.海藻式MBR能够降低MBR膜丝根部的污染,清洗更方便、更有效.     

不同污泥龄下MBBR-MBR和MBR的脱酚脱氮性能比较

通过平行运行MBBR-MBR和MBR,保持进水水质和其他操作条件相同的条件下,对比两个反应器在不同污泥龄下对NH3-N、COD、TN和间甲酚的降解效率,分析MBBR－MBR和MBR各自的脱酚脱氮性能。试验表明：不同污泥龄下MBBR—MBR的处理效率均。蒋于MBR。当污泥龄为8d时,MBBR－MBR对NH3-N的去除效率是MBR的2．4倍：当污泥龄为20d时,MBBR－MBR对NH3－N、TN、COD、间甲酚的去除效率分别为95．4％、82．6％、99．4％和99．6％。     

Enhancing Biodegradability of Textile Wastewater by Ozonation Processes: Optimization with Response Surface Methodology

ABSTRACT

In this study, an ozonation process was used to increase biodegradability of textile wastewater by considering chemical oxygen demand (COD) and color removal. Response surface methodology was applied in order to determine the significance of independent variables which are initial pH, reaction time and ozone dose. While a biological oxygen demand (BOD)/COD rate of 0.315 was obtained at optimum conditions, which are pH 9, 75 min of reaction time and 26 mg/L ozone dose, color and COD removal was obtained at 74% and 39%, respectively. BOD/COD ratio value increased from 0.18 to 0.32 by ozonation process. In addition, k coefficient for BOD also increased from 0.21 to 0.30 d^?1.     

The optimization of the photo-oxidation parameters to remediate wastewater from the textile dyeing industry in a continuous stirred tank reactor

The remediation of textile dying wastewater was carried out at ambient temperatures in a pilot-scale continuous stirred tank reactor by using the photo-Fenton oxidation process. The preliminary results suggest that the treatment system reached a steady state condition within 5–10 min after it was started up. By using a 2 ^k factorial design, the effects of various parameters on the removal efficiency of color, BOD and COD were identified under steady state conditions. The removal efficiencies of color and BOD were affected by the feed rate of H₂O₂ and Fe²⁺, whereas none of the parameters in the investigated ranges affected the removal efficiency of COD. Consequently, using univariate analysis to investigate higher parameter range values, the optimum conditions for treating textile wastewater were found to be 25 ml H₂O₂/min, 5 ml Fe²⁺/min and 90 W UV-A power for 20 min. In addition, the removal of all pollutants was enhanced within the acidic pH range. Approximately 69.2, 99.4 and 48.5% of color, BOD and COD were removed, respectively. However, the concentration of TDS increased slightly during the treatment period due to the formation of new species or intermediate oxidation products. Nevertheless, all values of pollutants in the treated wastewater except COD were in the range of the standard values permitted for discharge into the environment.     

The Study on the Ceramic Membrane Wastewater Reuse System with Pre-Ozonation and Coagulation

A new wastewater reuse system using ozonation, coagulation and MF ceramic membrane (0.1 μm) filtration was developed. The testing was performed using secondary effluent treated at the wastewater treatment plant (WWTP) in Tokyo, Japan. The volume of treated water by the pilot study equipment is about 90 m³/day. The combination of pre-ozonation and coagulation processes achieves continuous stable membrane filtration with flux of 4m³/m²/day (167 LMH). A stable membrane filtration could be maintained by controlling ozone dosing rate depending on secondary effluent (raw water) quality fluctuation. The COD (Mn) removal ratio in raw water was 50 to 60%, and the color removal ratio satisfied 80% or higher. The quality of the treated water that was obtained from our pilot study was better than the California's standards.     

Comparison of the operational characteristics between a nitrifying membrane bioreactor and a pre-denitrification membrane bioreactor process

A single submerged membrane bioreactor (MBR) for nitrification of ammonium and a pre-denitrification MBR process for total nitrogen (TN) removal were investigated in comparison. A single nitrifying MBR was fed with synthetic ammonium wastewater of up to 900 mgN/l without organics so that the MBR was maintained as a pure nitrifying system. A high nitrifying capacity around 1.8 kgNH₄-N/m³/day was achieved while keeping the ammonium oxidation rate above 98%. Sludge volume index (SVI) gradually decreased down to less than 50 indicating good settleability of nitrifying sludge. The increase of suction pressure was less than 5 cm Hg over 7-months of operation. TN removal efficiency was determined in a pre-denitrification configuration with an anoxic reactor. Synthetic wastewater of 1200 mgCOD/l and 200 mgN/l was fed to the system at loads of 2.4 kgCOD/m³/day and 0.4 kgN/m³/day, respectively. As the internal recycle ratio from aerobic to anoxic zone increased from 2 to 6, TN removal efficiency was enhanced from 70 ± 9 to 89 ± 3%. With the sludge concentration of around 12,000 mg/l, SVI was highly fluctuated from 60 to 350 indicating the partial deterioration of sludge settleability. The suction pressure after 8 months of operation increased to above 10 cm Hg which is higher than that in a single nitrifying MBR. The concentration of extracellular polymeric substances (EPS), especially for carbohydrate content, was higher in the operation of a pre-denitrification MBR process than in a single nitrifying MBR. It is likely that the sludge characteristic such as settleability is related with membrane fouling but, further extensive study is needed. The performance of a pre-denitrification MBR process was also verified with real petrochemical nitrogen wastewater.     

Application of A/O‐MBR for treatment of digestate from anaerobic digestion of cow manure

BACKGROUND: Anaerobic digestion (AD) is widely used as an animal manure bioconversion technology. However, the effluent obtained from the digester during the wet‐AD process requires to be treated carefully before discharge if AD technology is to be developed as an effective and environmentally advantageous animal manure treatment. RESULTS: An anoxic/aerobic‐membrane bioreactor(A/O‐MBR) system has been developed for digestate treatment in an AD system treating cow manure. The performance of the A/O‐MBR system in terms of removal of nitrogen, COD and phosphorus were investigated. Results indicated that the average removal efficiencies of NH₄‐N⁺, COD and PO₄^3?‐P were 98.1%, 96.3% and 76.6%, respectively. The fouled membrane from the A/O‐MBR system was cleaned effectively using NaOH and a 30h soak time. CONCLUSION: This study suggests that it is technically feasible to use the A/O‐MBR for the treatment of digestate from a cow manure AD system, and can provide an environmentally acceptable way for the application of wet‐AD in animal manure treatment. Copyright © 2010 Society of Chemical Industry     

单级膜生物反应器处理生活污水的研究

对单级膜生物反应器（MBR）处理生活污水进行了研究,考察了在四种工况下反应器对COD和氮的去除效果及其影响因素。试验结果表明：反应器对COD具有很好的去除效果,去除率在93％以上;对于氮的去除,反硝化是该工艺的关键控制步骤,通过改变运行工况和增加污泥浓度,使NH^＋4-N的去除率达90％以上,TN的去除率达83％以上。     

MBR-光催化氧化处理印染废水的试验研究

利用MBR-光催化氧化的组合工艺处理某纺织园区综合废水,对反应装置进行了连续运行效果的考察.结果表明,MBR对废水COD、浊度,色度降解率分别达到93.5%、99.9%和98.9%;MBR中污泥沉降性能明显优于SBR,能有效控制污泥膨胀现象;出水的透光性大大提高,经光催化氧化后COD、BOD、浊度、色度分别稳定在35.0mg·L~(-1)、2.7 mg·L~(-1),2.3NTU、3倍,水质达到GB 18918-2002的一级A排放标准和CJ/T48-1999的生活杂用水要求.     

Osmotic urine fuel cell to recover water,energy, and nutrients along with salinity reduction

An osmotic urine fuel cell (OsUFC) was employed to recover water, energy, and nutrients from urine. The recovered water was used to reduce the salinity of the brine solution. The water flux of concentrated urine (2.83 LMH) was lower than that of diluted urine (4.72 LMH); however, the current output was higher due to the high conductivity. Besides, the water flux of concentrated urine was improved significantly from 1.91 to 5.09 LMH by varying NaCl concentrations from 0.5 to 3 M, respectively. Similarly, the current production was enhanced from 4.07 to 61.20 mW m^?3 for the NaCl concentrations from 0.5 to 3 M, respectively. Moreover, OsUFC displayed nutrient rejection rates of 100%, 90%, 99%, and 96% for PO₄^3?, TN, NH₄⁺–N, and TOC, respectively. Furthermore, OsUFC showed salinity reduction efficiencies of 25.15% and 32.28% for Na⁺ and Cl^?, respectively.

Graphical abstract

     

Biological nutrient removal characteristics of low strength municipal wastewater

Most Korean community represents the primary effluent of 180 mg/L COD, 80 mg/L BOD, 25 mg/L TKN and 4 mg/L TP. A/O, A²/O and MUCT (Modified University of Cape Town) systems were applied to laboratory scale reactor with a temperature of 10 to 20°C. A total of 6 hour hydraulic retention time including anaerobic, anoxic and aerobic zones was used with a maximum 3,000 mg/L MLSS to simulate the existing municipal plants. All BNR systems represented effluent BOD less than 10 mg/L. MUCT produced better quality; 0.5 mg/L SP (soluble phosphorus) with 10 mg/L TN vs 1.8 mg/L SP with 12 mg/L TN for A²/O with the same internal recycle ratio. Performance of BNR systems would suggest the primary effluent used for this study represents a nature of slowly biodegradable COD. As that result, anaerobic fraction must be increased to attain lower effluent P concentrations. However, prefermentation to increase Premoval was not necessary since P was also limited. Microbial mass fractions computed from COD and nitrogen mass balances suggested that poly-P microbes were about 33% in A/O and MUCT, denitrifier fractions were about 30% in A²/O and MUCT. Nitrifier fractions were about 2%.     

Treatment of high‐fat‐containing dairy wastewater in a sequential UASBR system: influence of recycle

BACKGROUND: Raw cheese whey originating from white cheese production results in a strong and complex wastewater excessively rich in organic matter (chemical oxygen demand, COD = 28–65 g L^?1), fatty matter (14–24.5 g L^?1) and acidity (3.9–6.1 g L^?1). It was treated in a three‐stage configuration consisting of a pre‐acidification (PA) tank and sequential upflow anaerobic sludge bed reactors (UASBRs) at 2.8–7 g COD L^?1 day^?1 organic loading rates, during which the effects of effluent recycling at low rates and promoted SRB activity were investigated. Acidification, volatile fatty acids (VFA), COD and fatty matter removal and volatile solids were monitored throughout the system during the study. RESULTS: Recycling of the effluent promoted VFA and COD removal as well as pH stability in both stages of the UASBRs and the effluent where high alkalinity levels were recovered reducing alkali requirement to 0.05 g OH g^?1 COD_applied. Higher removal rates of 71–100 and 50–92% for VFA and COD were obtained by use of recycling. Fatty matter was removed at 63–89% throughout the study. Volatile solids build‐up was significant in the inlet zones of the UASBRs. CONCLUSIONS: The system produced efficient acidification in the PA tank, balanced pH levels and an effluent high in alkalinity and BOD/COD ratio. Efficient VFA removal and solids immobilization was obtained in both stages up to the highest loading rate. Recycling improved the system performance under high fatty matter loading conditions. A major advantage of the sequential system was that the second stage UASBR compensated for reduced performance in the first stage. Copyright © 2010 Society of Chemical Industry     

Anaerobic and aerobic treatment of a simulated textile effluent

A simulated textile effluent (STE) was generated for use in laboratory biotreatment studies; this effluent contained one reactive azo dye, PROCION Red H‐E7B (1.5 g dm⁻³); sizing agent, Tissalys 150 (1.9 g dm⁻³); sodium chloride (1.5 g dm⁻³) and acetic acid (0.53 g dm⁻³) together with nutrients and trace elements, giving a mean COD of 3480 mg dm⁻³. An inclined tubular anaerobic digester (ITD) was operated for 9 months on the STE and a UASB reactor for 3 months. For a 57 day period anaerobic effluent from two reactors, a UASB and an ITD, was mixed and treated in an aerobic stage. In days 77–247 68% of the true colour of PROCION Red H‐E7B was removed by anaerobic treatment with no colour removal aerobically and up to 37% COD was removed anaerobically, with a corresponding BOD removal of 71%. For combined anaerobic and aerobic treatment a mean COD removal of 57% and BOD removal of 86% was achieved. Operation of the ITD at a 2.8 day HRT (volumetric loading rate (B _v) 1.24 g COD dm⁻³day⁻¹) and the UASB at a 2 day HRT (B _v 1.74 g COD dm⁻³day⁻¹) gave comparable COD removals but the UASB gave better true colour removal. Effluent from the combined process operating on this simulated waste still contained an average 1500 mg COD dm⁻³, and further treatment would be required to meet consent standards. © 1999 Society of Chemical Industry     

SRT对膜生物反应器出水水质的影响及其控制途径的研究

膜生物反应器中MLVSS为4000-5000mg／L时,COD的去除率可达98％左右,但随SRT的继续延长,污泥浓度的增加,使得内源呼吸加剧和大量微生物死亡,导致上清液COD上升,SMPnd含量增加,出水COD存在波动性,但COD的去除率仍在94％左右。高污泥浓度下的MBR反应器中投加粉末活性炭后,由于粉末活性炭对SMPnd有很强的吸附作用,因此反应器对COD的去除率增加。