Electrocoagulation technique in enhancing COD and suspended solids removal to improve wastewater quality.

This paper presents a preliminary study for the removal of COD and suspended solids in wastewater treatment by combining magnetic field and electrocoagulation (EC) technology. The experiments were carried out using batch apparatus and setup in the static method. Batch experiments with two monopolar iron (Fe) plate anodes and cathodes were employed as electrodes. Wastewater samples were prepared from milk powder with an initial COD of 1,140 mgL(-1) and suspended solids of 1,400 mgL(-1) and acidic conditions were employed (pH approximately 3). DC current was varied from 0.5-0.8 A and operating times were between 30 and 50 min. The results show that the effluent wastewater was very clear (turbidity approximately 9 NTU) and its quality exceeded the direct discharge standard. The suspended solids and COD removal efficiencies were as high as 30.6 and 75.5%, respectively. In addition, the experimental results also show that the electrocoagulation could neutralise the pH of wastewater.     

板间距对电絮凝处理微污染水的影响

电絮凝作为一种具有广泛应用前景的低廉高效污水处理技术,已经被证明在工业废水、生活污水等污染严重的水体处理上具有显著效果,但是目前对于电絮凝净化微污染水的相关研究较少。通过对电絮凝分批处理河水的实验研究,分析电絮凝方法处理微污染水的可行性,讨论极板间距的改变对电絮凝处理效果的影响。结果表明,电絮凝处理技术可以用于微污染水净化中,在电流密度为17.75 A/m2、极板间距为1.5 cm的条件下,反应30 min时,色度去除率为73.76%,浊度去除率为76.00%,悬浮固体去除率为85.71%,化学需氧量去除率为42.86%,总磷去除率为61.36%。在电絮凝反应中,极板间距对于微污染水的色度、浊度、悬浮固体和总磷去除效果具有明显的影响。     

Advanced phosphorus removal for secondary effluent using a natural treatment system

Mechanisms for low concentrations phosphorus removal in secondary effluent were studied, and a process was developed using limestone filters (LF), submerged macrophyte oxidation ponds (SMOPs) and a subsurface vertical flow wetland (SVFW). Pilot scale experimental models were applied in series to investigate the advanced purification of total phosphorus (TP) in secondary effluent at the Chengjiang sewage treatment plant. With a total hydraulic residence time (HRT) of 82.52 h, the average effluent TP dropped to 0.17 mg L(-1), meeting the standard for Class III surface waters. The major functions of the LF were adsorption and forced precipitation, with a particulate phosphorus (PP) removal of 82.93% and a total dissolved phosphorus (TDP) removal of 41.07%. Oxygen-releasing submerged macrophytes in the SMOPs resulted in maximum dissolved oxygen (DO) and pH values of 11.55 mg L(-1) and 8.10, respectively. This regime provided suitable conditions for chemical precipitation of TDP, which was reduced by a further 39.29%. In the SVFW, TDP was further reduced, and the TP removal in the final effluent reached 85.08%.     

H_2O_2与沸石联用处理污水厂二级出水的研究

为探寻污水厂二级出水深度处理方法,以阜新市某污水处理公司二级出水为研究对象,进行H2O2与沸石联用去除水中COD、氨氮的研究。结果表明：在二氧化锰的催化作用下,pH值为7时,H2O2和沸石的投加量分别为1.5mL和2g,二级出水的COD从138.24mg/L降到52.76mg/L,去除率达到75.36%,NH3-N从20mg/L降到5mg/L,去除率为74.59%,出水有机物和氨氮含量达到国家相关出水标准。     

Enhanced biological phosphorus removal in RBC with SBR modification.

The rotating biological contactor (RBC) system was operationally modified with a sequencing batch reactor to achieve biological phosphorus removal from a weak domestic sewage along with nitrogen removal. This study utilized three RBC units, of which two units were the main units to remove phosphorus and NH4N and the third RBC unit was used as the storage of wastewater for its minimal effect to the PAO activities in the anaerobic stage during the operation. It was noticed that the biofilm thickness in RBC must be controlled to be less than 1.8 mm in order to achieve more than 70% of P removal with about 60% of N removal. With a settled sewage representing 200 mg/L of COD and 5 mg/L of P, the predicted P content in biofilm was more than 3% and the effluent P concentration was about 1 mg/L. The %P content in biofilm decreased with an increase of influent COD/TP ratios. The COD requirement for anaerobic P release was similar to reported values for the suspended growth system, however, the overall requirement increased with thicker biofilm.     

Enhancing phosphorus removal in constructed wetlands with ochre from mine drainage treatment.

No single end-use has yet been identified that is capable of consuming the projected production of ochre (mainly iron (III) oxides) from mine drainage treatment. However, the high sorption capacity of ochre for phosphorus (up to 26 mg kg(-1)) means that it could be used in constructed wetlands to enhance phosphorus removal. Laboratory batch experiments showed that coarse-grained ochre removes 90% of all phosphorus forms from sewage effluent after 15 minutes of shaking. From a larger-scale experiment, it is estimated that constructed wetlands with an ochre substrate should remove phosphorus from sewage effluent for up to 200-300 years. The suitability of ochre for phosphorus removal is being investigated at the field scale in a wastewater constructed wetland (175 m2 area) in Berwickshire, UK. The hydraulic and treatment performance of the wetland were monitored for 15 months prior to installation at the inlet in November 2003 of a tank containing approximately 1200 kg ochre. Results so far show that improved hydraulic design is required for ochre to increase the mean phosphorus removal efficiency of the system (27 +/- 28%), but potentially toxic metals (Al, Cd, Cr, Cu, Fe, Ni, Pb, Zn) have not been released from the ochre into the wetland outflow.     

生物慢滤池用于污水深度处理的实验研究

利用生物慢滤池对人工模拟污水和西安市某污水处理厂的二级出水进行了深度净化处理实验,通过分析进出水中氮、磷含量和高锰酸盐指数及上层水和出水中的叶绿素a含量等指标,考察了生物慢滤池的净化效果。结果表明:生物慢滤池对人工模拟污水的处理效果较好,总氮、氨氮、总磷和高锰酸盐指数的去除率分别为66.4%、40.2%、66.4%和73.3%;深度净化污水厂二级出水,总氮、氨氮、总磷和高锰酸盐指数的去除率分别为35.1%、21.0%、30.2%和12.6%,去除率略低于人工模拟实验;生物慢滤池对叶绿素a有很好的截留效果,去除率分别为93.4%和66.4%;生物慢滤池处理后的再生水水质达到《城市污水再生利用景观环境用水水质》要求,可回用于城市景观水体,作为城市景观水体的补充水源,避免水体富营养化的发生。     

深圳市布吉污水处理厂构建人工湿地试验研究

为了最大程度地改善深圳市布吉河水质状况,在先期进行布吉污水处理厂中试试验的基础上,建设了小型人工湿地,深度处理污水处理厂二级出水,探讨污水处理厂二级出水在人工湿地基础上的改善程度,为该市布吉污水处理厂建设完成后是否规划建设景观湿地提供参考依据。结果表明:人工湿地对二级出水的COD、NH3-N、TN、TP等重要控制指标均有比较明显的深度处理作用;夏季的运行效果总体上比秋、冬季处理效果好,季节变化对TN去除率的影响最为明显,但对出水COD、NH3-N、TP指标影响相对较小。     

Operation of a new sewage treatment process with technologies of excess sludge reduction and phosphorus recovery.

This paper shows the potential application of a new sewage treatment process with technologies of excess sludge reduction and phosphorus recovery. The process incorporated ozonation for excess sludge reduction and crystallisation process for phosphorus recovery to a conventional anaerobic/oxic (A/O) phosphorus removal process. A lab-scale continuous operation experiment was conducted with the ratio of sludge flow rate to ozonation tank of 1.1% of sewage inflow under 30 to 40 mgO3/gSS of ozone consumption and with sludge wasting ratio of 0.34% (one-fifth of a conventional A/O process). Throughout the operational experiment, a 60% reduction of excess sludge production was achieved in the new process. A biomass concentration of 2300 mg/L was maintained, and the accumulation of inactive biomass was not observed. The new process was estimated to give a phosphorus recovery degree of more than 70% as an advantage of excess sludge reduction. The slight increase in effluent COD was observed, but the process performance was maintained at a satisfactory level. These facts demonstrate an effectiveness of the new process for excess sludge reduction as well as for phosphorus recovery.     

Integrated advanced natural wastewater treatment system for small communities.

A study was conducted to evaluate the nutrient removal capability of an existing and successfully operated overland flow and wetland wastewater treatment system following a waste stabilization pond. Seasonal temperature effects on performance were also investigated. The treatment system studied consists of a two-cell waste stabilization pond followed by an overland flow system and a wetland system. The influent and effluent samples were analyzed for BOD5, suspended solids (SS), pH, temperature, ammonia nitrogen, nitrate nitrogen, and total phosphorus. The results of the study indicate that the combined pond, overland flow and wetland system provided excellent treatment of municipal wastewater. The overall average BOD5 removal by the entire treatment system was about 90.0% and the overall average suspended solids removal was about 93.4%. The ammonia nitrogen and total phosphorus removal efficiencies of the entire treatment system were 90.7% and 84.2%, respectively.     

Removal of boron (B) from waste liquors.

This paper explores the use of electrocoagulation to remove boron from waste effluent in comparison with alum coagulation. In treating model test wastes, greater boron removals were achieved with electrocoagulation at low doses than conventional alum coagulation when reaction was undertaken for the same conditions (pH 8.5, and initial boron concentration was 500 mg/L). Al electrocoagulation can achieve good boron removal performance (68.3%) at a dose of 2.1 (as molar ratio of Al:B, and for current density of 62.1 A/m2), while alum coagulation can only achieve the maximum boron removal of 56% at a dose of 2.4. Also, Al electrocoagulation can remove 15-20% more boron than alum coagulation for the same dose compared in the treatment of both model test wastes and industry effluent. The estimation of running costs shows that to achieve 75% boron removal from industry waste effluent, i.e. removing 150 g of boron from 1 m3 of effluent, electrocoagulation was 6.2 times cheaper than alum coagulation. The economic advantage of electrocoagulation in the treatment of boron-containing waste effluent is thus significant.     

DO对短程同步硝化反硝化除磷工艺的影响

针对碳源偏低的城市污水,采用序批式活性污泥法研究D0对短程同步硝化反硝化除磷工艺的影响,同时对短程同步硝化反硝化和反硝化除磷的机理进行探讨。试验表明：控制DO浓度可在同一个反应器内既实现短程同步硝化反硝化反应又达到反硝化除磷的效果。综合考虑COD、NHg—N、TN、TP的出水浓度达到一级A排放标准,得出最佳的D0控制范围。当D0浓度在0．5～1．0mg／LU时．COD的去除率达到93％～94％,Nil,＋一N的去除率为97％～98％,TN的去除率达到85％一96％,TP的去除率为91％～93％。     

Comparison of electrocoagulation, coagulation and the fenton process for the treatment of reactive dyebath effluent.

In this paper, experimental studies were performed on a simulated reactive dyebath effluent to compare coagulation-flocculation and Fenton's oxidation with electrocoagulation using stainless steel (SS 304) and aluminium electrodes in terms of colour and COD removals as well as AOX formation potential and improvement of biological treatability. Results have indicated that FeCl3 and alum coagulation had little effect on colour removal whereas comparable colour removal efficiencies with those of electrocoagulation with steel electrodes and Fenton's oxidation were attained by FeSO4 coagulation. Almost complete colour removals accompanied with 77% COD abatement were obtained by both electrocoagulation with steel electrodes and Fenton's oxidation under optimised reaction conditions. Although electrocoagulation with aluminium electrodes yielded very limited colour removal and produced a high amount of sludge upon extended reaction time, this application brought about a marked improvement in biodegradability.     

Phosphorus removal by laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate

This research aimed to investigate the phosphorus (P) removal of a series of laboratory-scale unvegetated vertical-flow constructed wetland systems using anthracite, steel slag and related blends as substrate in treatment of low concentration domestic sewage. The long-term performance of P removal was firstly studied by using single substrate of anthracite or steel slag, and three systems applying various combined substrates were investigated when the average P loading rate varied between 0.9 and 1.5 g TP/m2 x d. The results demonstrated that both anthracite and steel slag systems were highly effective in removing total P (CTP, 77.17 +/- 23.34% and 90.26 +/- 4.48%) and soluble reactive P (SRP, 92.14 +/- 12.56% and 96.20 +/- 2.58%). The system filled with anthracite, vermiculite and steel slag from the top down removed 82.45 +/- 9.52% and 87.83 +/- 8.58% of TP and SRP, respectively. However, other combined substrate systems showed comparative low and fluctuant P removal. The effluent pH was maintained at 7-9, which met environmental requirements of China. Therefore, anthracite provides a long-term high efficiency of P removal and may be a promising substrate from the standpoint of the effluent pH, and the arrangement of combined substrate has a prominent effect on P removal.     

农村污水生物泳动床处理技术研究

生物泳动床工艺是一种采用新型、高效生物填料的生物膜污水处理方法,是生物接触氧化工艺的改进。对农村污水具有很好的处理效果,通过试验发现填料挂膜速度快,一般只需1周左右的时间即可完成。生物填料膜没有集中脱落或闭塞现象、无需反冲洗。COD从250mg/L增到700mg/L,出水COD去除率仍然高达90%以上,出水平均氨氮小于5mg/L,出水平均TN小于20mg/L,TN去除率60%以上。通过调节运行参数和进水水质的试验研究,最终确定出生物泳动床高效低成本的工艺运行参数。     

Treatment of swine wastewater using MLE process and membrane bio-reactor.

The aim of this study was to develop the optimum integrated treatment system for slurry type swine wastewater through field testing. Although composting and liquid composting are the most desirable processes to treat swine wastewater, inadequate composting has been blamed as critical non-point source pollutants. In the area with limited crop land and grass land, the most feasible method to handle slurry type swine wastewater would be that the solids portion from the solids/liquid separation process is treated by composting and then the liquid portion is treated by a series of wastewater treatment processes, including physicochemical treatment system and biological nutrient removal systems such as the modified Ludzack Ettinger (MLE) process and MLE process coupled with a membrane, to satisfy the different effluent criteria. When using the appropriate solids/liquid separation system, the removal efficiency of SS, COD(Cr), and TKN was 92.4%, 73.6%, and 46.0%, respectively and the amount of bulking agent required for composting and organic loading rate for the following wastewater treatment system can be reduced by 94.8% and 84.7%, respectively. When treating the effluent from solids/liquid separation process by MLE process, the optimal volume fraction for denitrification was 20% of total reactor volume and the optimum ratio of F/M and F(N)/M were increased with increase of C/N ratio. Since the effluent quality of MLE process is not enough to discharge, the DAF process was operated with addition of FeCl3 and cationic polyelectrolyte. The effluent from the DAF process was treated in the MLE process coupled with a crossflow ultrafiltration membrane to satisfy more stringent effluent criteria. When external carbon source is added to keep 6.0 of C/N ratio, the efficiency of denitrification is best. The optimum linear velocity and transmembrane pressure for MBR process was 1.8 m/sec and 2.1 atm, respectively. By addition of external carbon source, nitrogen compounds, especially NOx-N, were considerably removed. And by addition of powdered activated carbon, the removal efficiency of COD(Cr) and COD(Mn) and the membrane flux were increased dramatically.     

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.     

折流式曝气生物滤池设备的开发及应用研究

针对三峡库区小城镇生活污水处理特点,研发折流式曝气生物滤池(BBAF)设备,通过将多级串联组合式BAF集成在同心圆式反应器内,形成了良好的力学性能和水力条件.在设计参数下运行时,对SS、COD、NH3-N、TN和TP的平均去除率分别为76％、83％、97％、26％和45％.高气水比有利于COD和NH3-N的去除,但会削弱TN、SS的去除效能,BBAF适宜的气水比为9.当处理负荷在1.5～3.0 m3/h范围内变化时,SS、COD和NH3-N的平均去除率无明显波动,出水水质稳定,表明设备具有较强的抗冲击负荷能力,对小城镇污水量变化系数大的特点具有很好的适用性.     

Electrically enhanced MBR system for total nutrient removal in remote northern applications

Thousands of sparsely populated communities scatter in the remote areas of northern Canada. It is economically preferable to adopt the decentralized systems to treat the domestic wastewater because of the vast human inhabitant distribution and cold climatic conditions. Electro-technologies such as electrofiltration, elctrofloatation, electrocoagulation and electrokinetic separation have been applied in water and conventional wastewater treatment for decades due to the minimum requirements of chemicals as well as ease of operation. The membrane bioreactor (MBR) is gaining popularity in recent years as an alternative water/wastewater treatment technology. However, few studies have been conducted to hyphenate these two technologies. The purpose of this work is to design a novel electrically enhanced membrane bioreactor (EMBR) as an alternative decentralized wastewater treatment system with improved nutrient removal and reduced membrane fouling. Two identical submerged membranes (GE ZW-1 hollow fiber module) were used for the experiment, with one as a control. The EMBR and control MBR were operated for 4 months at room temperature (20 ± 2 °C) with synthetic feed and 2 months at 10 °C with real sewage. The following results were observed: (1) the transmembrane pressure (TMP) increased significantly more slowly in the EMBR and the interval between the cleaning cycles of the EMBR increased at least twice; (2) the dissolved chemical oxygen demand (COD) or total organic carbon (TOC) in the EMBR biomass was reduced from 30 to 51%, correspondingly, concentrations of the extracellular polymeric substances (EPS), the major suspicious membrane foulants, decreased by 26-46% in the EMBR; (3) both control and EMBR removed >99% of ammonium-N and >95% of dissolved COD, in addition, ortho-P removal in the EMBR was >90%, compared with 47-61% of ortho-P removal in the MBR; and (4) the advantage of the EMBR over the conventional MBR in terms of membrane fouling retardation and phosphorus removal was further demonstrated at an operating temperature of 10 °C when fed with real sewage. The EMBR system has the potential for highly automated control and minimal maintenance, which is particularly suitable for remote northern applications.     

Modeling of enhanced biological phosphorus removal in a sequencing batch biofilm reactor

A biofilm system operated for enhanced biological phosphorus removal is evaluated using a mathematical model. The influence of the influent COD concentration and the biofilm thickness are investigated. In an activated sludge system increasing the influent COD will result in a decrease of the effluent phosphorus concentration. However, in a biofilm system above a certain influent COD concentration not all COD supplied in the influent can be taken up during the anaerobic period. Other heterotrophic bacteria will then dominate the biofilm resulting in an increase of the effluent phosphorus concentration. A larger biofilm thickness will result in an increase of the total mass of polyphosphate-accumulating organisms in the system. However, it is shown that a larger biofilm thickness results in higher effluent phosphorus concentrations. The mathematical model presented is based on the IAWQ Model No. 2 modified for the biofilm system. Mass transport in the biofilm is modeled one-dimensionally. Removal of biomass through backwashing and, thus, removal of phosphorus, is included in the mathematical model. Simulations were used to explain experimental observations.