Aspects of design, structure, performance and operation of reed beds--eight years' experience in northeastern New South Wales, Australia.

Reed beds (horizontal subsurface flow constructed wetlands) have been employed as secondary treatment devices in on-site and decentralised wastewater management systems in the northeast of the Australian state of New South Wales (NSW) for over a decade. This paper summarises some of the practical and research findings that have come to light in that time. Experience with various aspects of reed bed structure is discussed. A study of the evaporative performance of four small beds planted with Phragmites australis yielded an annual crop factor of 2.6. A total of 28 studies on reed beds treating a variety of commonly encountered wastewater streams yielded the following mean pollutant removal efficiencies: total suspended solids (TSS) 83%, biochemical oxygen demand (BOD) 81%, total nitrogen (TN) 57%, total phosphorus (TP) 35% and faecal coliforms (FC) 1.9 logs. The reed bed is becoming the preferred on-site technology for removing TN and BOD and polishing TSS from primary settled domestic wastewater. Sizing beds for a residence time of approximately five days has become standard practice. A study of six reed beds found six different species of earthworm present, mainly Perionyx excavatus (Indian Blue). A mesocosm experiment subsequently showed that the worms were translocating clogging material from the substrate interstices to the surface of the bed thereby indicating a possible method for prolonging reed bed life.     

Nutrient reduction evaluation of sewage effluent treatment options for small communities.

Small communities that are sewered by either package sewage treatment plants or on-site sewerage facilities are finding that the ground and surface waters are being contaminated. Nitrogen, which typically is not removed in these conventional systems, is a major concern. This project evaluated the capability of four sewage treatment technologies to reduce the amount of nitrogen being discharged in the effluent to the receiving environment. The four sewage treatment processes evaluated include a recirculating sand filter, biofilter, slow sand filter and constructed subsurface flow wetland. These processes were evaluated for their capability to reduce nitrogen, phosphorus, BOD5 and TSS. The primary objective of the project was to evaluate the capability of these treatment processes to reduce nitrogen using biological processes nitrification and denitrification. This paper reports on the performance of these processes to reduce nitrogen. The study demonstrated that the biofilter was capable of removing from a primary treated influent 40% of the total nitrogen. For the same quality influent the recirculating sand filter was capable of removing 35% of the total nitrogen. Secondary treated effluent was fed to the slow sand filter and the subsurface flow wetland. There was a 52% reduction in total nitrogen through the wetland however there was virtually no reduction in total nitrogen through the slow sand filter.     

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。     

Application of membrane bioreactor system with full scale plant on livestock wastewater.

A full-scale plant of an MBR system treating livestock wastewater has shown impressive results. The Cheorwon County Environmental Authorities adopted the MBR process with UF membrane for retrofitting the old plant, which removes organic matter, nitrogen and phosphorus at a high level. According to 6 months operation data, BOD and SS removal were about 99.9% and COD(Mn), TN and TP removal were 92.0%, 98.3% and 82.7%, respectively. It is considered that the temperature at the bioreactor has to be controlled to be below 40 degrees C so as to ensure sufficient nitrification. It appeared that the MBR system is competitive with other conventional technologies for treatment of livestock wastewater such as piggery waste.     

Performance of a combined eco-system of ponds and constructed wetlands for wastewater reclamation and reuse.

An on-site study on the operational performance of a combined eco-system of ponds and SF constructed wetland for municipal wastewater treatment and reclamation/reuse in Donging City, Shandong, China was carried out from January 2001 through October 2003. The removal efficiencies for various main parameters were: TSS 84.8 +/- 7.3%, BOD5 87.2 +/- 5.3%, CODCr 70.2 +/- 18.6%, TP 52.3 +/- 23.1%, and NH(3)-N 54.8 +/- 23.9% with effluent concentration of TSS 9.12 +/- 5.12 mg/l, BOD5 6.44 +/- 4.58 mg/l, CODCr, 42.8 +/- 6.7 mg/l, TP 0.94 +/- 0.27 mg/l and NH(3)-N 7.95 +/- 2.36 mg/l. In addition, the removal efficiencies for faecal coliforms and total bacteria were > 99.97% and > 99.998% respectively, which well meet Chinese National standards for effluent quality of municipal wastewater treatment plants. The composition of TSS was closely related to CODCr and BOD5 variations, and nitrification-denitrification is the major mechanism of nitrogen removal both in ponds and in wetlands. In addition, sedimentation also played an important role in the removal of TSS, nitrogen, phosphorus and BOD5. The removal efficiencies of various parameters, the number of species and biomass of biological community in the system increased gradually with the ecological maturation.     

Kinetic study of slaughterhouse wastewater treatment by electrocoagulation using Fe electrodes

In this study, treatment of slaughterhouse wastewater by electrocoagulation was investigated in batch system using Fe electrodes. The effect of various variables such as electrode number, current density and operating time was tested. Pollutant removal efficiency increased with increasing electrode number and operating time. The biochemical oxygen demand (BOD(5))(,) chemical oxygen demand (COD), total suspended solid (TSS), and total nitrogen (TN) removal efficiencies using eight electrodes at a contact time of 50 min and a current density of 10 A/m(2) were 66, 62, 60, and 56%, respectively. Higher electrode numbers will allow shorter operating times to achieve certain removal efficiencies. Also, removal efficiencies increased by increasing the current density; the highest removal efficiencies of BOD(5,) COD, TSS, and TN at a contact time of 50 min and a current density of 25 A/m(2) were 97, 93, 81, and 84%, respectively. The results also show that the reactor pH varies directly with the current density; at 25 A/m(2), the reactor pH increased from an initial value of 7.1 to 7.7 after 50 min. The experimental results showed that the kinetics of BOD(5), COD, TSS and TN removal could be fitted adequately using a first order kinetic model (higher R(2)).     

Nitrogen mass balance and microbial analysis of constructed wetlands treating municipal landfill leachate.

Experiments were conducted to investigate the feasibility of applying constructed wetlands (CW) to treat a sanitary landfill leachate containing high nitrogen (TN) and bacterial contents. Under the tropical conditions (temperature of about 30 degres C), the CW units operating at a hydraulic retention time (HRT) of 8 days yielded the best treatment efficiencies with BOD5 removal of 91%, TN removal of 96%, total and fecal coliforms (TC and FC) removal of more than 99%. Cadmium removal in the in the SFCW bed was found to be 99.7%. Mass balance analysis, based on TN contents of the plant biomass and dissolved oxygen (DO) and oxidation - reduction potential (ORP) values, suggested that 88% of the input TN were uptaken by the plant biomass. Fluorescence in situ hybridization (FISH) results revealed the predominance of bacteria including the heterotrophic and autotrophic bacteria responsible for BOD5 removal. Nitrifying bacteria was not found to be present in the SSFCW beds.     

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.     

Behaviour of a full-scale expanded bed reactor with overlaid anaerobic and aerobic zones for domestic wastewater treatment.

This paper presents the behaviour of a full-scale expanded bed reactor (160 m3) with overlaid anaerobic and aerobic zones used for municipal wastewater treatment. The research was carried out in two experimental steps: anaerobic and anaerobic-aerobic conditions, and the experimental results presented in this paper refer to four months of reactor operation. In the anaerobic condition, after inoculation and 60 days of operation, the reactor treating 3.40 kg CODm(-3)d(-1) for thetaH of 2.69 h, reached mean removal efficiencies of 76% for BOD, 72% for COD, and 80% for TSS, when the effluent presented mean values of 225 mg.L(-1) of COD, 98 mg.L(-1) of BOD and 35 mg.L(-1) of TSS. Under these conditions, for nitrogen loading of 0.27 kgN.m(-3)d(-1), the reactor generated an effluent with mean N-org. of 8 mg.L(-1) and N-ammon. of 37 mg.L(-1), demonstrating high potential of ammonification. For the anaerobic-aerobic condition (118th day) the system was operated with thetaH of 5.38 h presented mean removal efficiencies of 84% for BOD, 79% for COD, 76% for TSS, and 30% for TKN. The reactor's operation time was less than two months, which was not long enough to reach nitrification. Regarding the obtained results, this research confirmed that this reactor is configured as a flexible and adequate alternative for the treatment of sewage, requiring relatively small area and only thetaH of 10 h that can be adjusted to the local circumstances.     

Evaluation of undersized bioretention stormwater control measures for treatment of highway bridge deck runoff

Two grassed bioretention cells were constructed in the easement of a bridge deck in Knightdale, North Carolina, USA, in October, 2009. One was intentionally undersized ('small'), while the other was full sized ('large') per current North Carolina standards. The large and small cells captured runoff from the 25- and 8-mm events, respectively. Both bioretention cells employed average fill media depths of 0.65 m and internal water storage (IWS) zones of 0.6 m. Flow-proportional, composite water quality samples were collected and analyzed for nitrogen species, phosphorus species, and TSS. During 13 months of data collection, the large cell's median effluent concentrations and loads were less than those from the small cell. The small cell's TN and TSS load reductions were 84 and 50%, respectively, of those achieved by the large cell, with both cells significantly reducing TN and TSS. TP loads were not significantly reduced by either cell, likely due to low TP concentrations in the highway runoff which may have approached irreducible levels. Outflow pollutant loads from the large and small cell were not significantly different from one another for any of the examined pollutants. The small cell's relative performance provides support for retrofitting undersized systems in urbanized areas where there is insufficient space available for conventional full-sized stormwater treatment systems.     

人工湿地污水处理系统优化设计模型

针对污水处理厂进水水质和水量的不确定性,考虑进水水量、TSS、BOD5、TN、TP的区间变化,以出水时TSS、BOD5、TN、TP的质量浓度标准为约束条件,单元面积为决策目标,以费用最小为目标函数,建立基于一级动力学污染物去除模型的人工湿地污水处理系统区间数优化设计模型。该模型包含初沉池、人工湿地床(表面流和潜流式)两个单元,考虑了设计中的不确定性因素。实例计算表明,模型适用性较好。     

Performance and microbial ecology of the hybrid membrane biofilm process for concurrent nitrification and denitrification of wastewater.

We report on a novel process for total nitrogen (TN) removal, the hybrid membrane biofilm process (HMBP). The HMBP uses air-supplying hollow-fibre membranes inside an activated sludge tank, with suppressed aeration, to allow concurrent nitrification and denitrification. We hypothesised that a nitrifying biofilm would form on the membranes, and that the low bulk-liquid BOD concentrations would encourage heterotrophic denitrifying bacteria to grow in suspension. A nitrifying biofilm was initially established by supplying an influent ammonia concentration of 20 mgN/L. Subsequently, 120 mg/L acetate was added to the influent as BOD. With a bulk-liquid SRT of only 5 days, nitrification rates were 0.85 gN/m(2) per day and the TN removal reached 75%. The biofilm thickness was approximately 500 lim. We used DGGE to obtain a microbial community fingerprint of suspended and attached growth, and prepared a clone library. The DGGE results, along with the clone library and operating data, suggest that nitrifying bacteria were primarily attached to the membranes, while heterotrophic bacteria were predominant in the bulk liquid. Our results demonstrate that the HMBP is effective for TN removal, achieving high levels of nitrification with a low bulk-liquid SRT and concurrently denitrifying with BOD as the sole electron donor.     

Subsurface constructed wetlands for wastewater treatment and reuse in agriculture: five years of experiences in Sicily, Italy.

The paper reports the results of an investigation on a H-SSF constructed wetland for tertiary treatment in a small community located in eastern Sicily, Italy. The system is designed to reuse wastewater for the irrigation of olive orchards covering about 150 hectares. From March 2001 to September 2005, wastewater samples were collected and the following chemical-physical parameters were determined according to Standard Methods: temperature, pH, EC, DO, TSS (105degrees C), BOD5, COD, TN, TP. The following microbiological parameters were also evaluated: total coliforms, faecal coliforms, Escherichia coli, faecal streptococci, Salmonella, helminth eggs. Mean removal efficiencies ranged from 77 to 92% (TSS), 37 to 72% (BOD5), 51 to 79% (COD), 97 to 99.5% (E. coli). Removal efficiency of Salmonella and helminth eggs was always 100% in all samples; however, only 150% of total samples matched the limit of E. coli (< 50 CFU/100 mL) fixed by Italian legislation for wastewater reuse.     

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.     

土壤过滤系统处理农村生活污水的 试验研究

采用一种土壤过滤系统处理农村生活污水,考察了该工艺对CODCr、BOD5、NH3-N、全氮（TN）和全磷（TP）的去除效果。实验结果表明,当水力负荷约为0.05 m3/（m2·d）, 水力停留时间为3 d时。该土壤过滤系统对CODCr、BOD5、NH3-N、全氮（TN）和全磷（TP）的去除效果较好,平均去除率分别达到84.6%、83.3%、64.3%、59.8%和70%。出水CODCr约为18.3~42.1 mg/L,BOD5约为8.9~17.3 mg/L,NH3-N约为11.2~17.7 mg/L,TN约为21.2~31.3 mg/L,TP小于2.0 mg/L,出水水质优于农田灌溉水质标准（GB 5084—2005）。气温变化和进水污染物浓度对处理效果影响明显。总体上来讲,温度大于22 ℃时,进水污染物浓度越低处理效果越好。     

Low effluent nutrient technologies for wastewater treatment.

The USEPA (2001) water quality nutrient criteria will have a significant impact on water pollution control industry due to stringent N and P requirements. This paper presents an update of findings on successful total N (TN) and total P (TP) technologies being implemented at existing wastewater treatment plants (WWTP) to achieve low TN and TP effluents and some key challenges in achieving lower levels. Plants consistently achieving <5 mg TN/L and < 0.5 mg TP/L were identified from a worldwide literature search and plant data collection. Technology gaps and research needs to improve successful technologies to achieve very low TN and TP effluents are summarised in this paper. The dissolved and colloidal organic N have been identified as major challenges in achieving very low levels of TN. Technical and economic challenges to achieve very low TP effluents include alkalinity deficiency, high chemical usage, high sludge production and lack of sufficient influent BOD for biological P uptake.     

Feasibility of UASB/trickling filter systems without final clarifiers for the treatment of domestic wastewater in small communities in Brazil

The paper analyses the concept and performance of different configurations of compact UASB/TF systems, without the final clarification stage, in relation to the removal of organic matter. The experiments were carried out in two sets of UASB/TF systems operating without secondary clarifiers, as follows: (i) four shallow (2.50 m height) TFs, each one filled with a different packing material; and (ii) two deep (4.20 m height) TFs, one filled with polyethylene corrugated sheets and the other with mixed polyethylene and sponge sheets. For the conditions tested (different packing material in shallow and deep TF), the UASB/TF systems had consistently complied (90 to 100% of the results) with the Brazilian discharge standards regarding to BOD, COD, and TSS parameters. The average BOD, COD and TSS effluent concentrations stayed below 40 mg BOD L(-1), 100 mg COD L(-1) and 50 mg TSS L(-1), respectively. UASB/TF systems can constitute an attractive alternative for domestic wastewater treatment in small communities in developing countries, especially considering its operational simplicity and very low running costs.     

Anaerobic co-digestion of sludge with other organic wastes and phosphorus reclamation in wastewater treatment plants for biological nutrients removal.

This paper deals with the performances obtained in full scale anaerobic digesters co-digesting waste activated sludge from biological nutrients removal wastewater treatment plants, together with different types of organic wastes (solid and liquid). Results showed that the biogas production can be increased from 4000 to some 18,000 m3 per month when treating some 3-5 tons per day of organic municipal solid waste together with waste activated sludge. On the other hand, the specific biogas production was improved, passing from 0.3 to 0.5 m3 per kgVS fed the reactor, when treating liquid effluents from cheese factories. The addition of the co-substrates gave minimal increases in the organic loading rate while the hydraulic retention time remained constant. Further, the potentiality of the struvite crystallisation process for treating anaerobic supernatant rich in nitrogen and phosphorus was studied: 80% removal of phosphorus was observed in all the tested conditions. In conclusion, a possible layout is proposed for designing or upgrading wastewater treatment plants for biological nutrients removal process.     

改良型人工快渗系统脱氮除磷效果研究

人工快渗(CRI)系统是一种广为人知的无动力生态处理技术措施,但传统CRI系统存在对氮、磷去除率普遍较低的问题。本研究采用海绵铁、沸石、火山岩、红壤土和杂沙作为填料,构建了一个改良型CRI系统,在水力负荷为1 m~3/(m~3·d)的条件下,以实际生活污水为试验进水,进行为期20天的试验。实验结果表明,该系统在运行16天后出水TP、TN和NH_3-N浓度均趋于稳定,稳定后出水平均浓度分别为0.21 mg/L、8.38 mg/L和2.34 mg/L,能分别满足《城镇污水处理厂污染物排放标准》(GB18918-2002)一级A排放标准的0.5 mg/L、15 mg/L和5 mg/L的限值。TP、TN和NH3-N三项指标的总平均去除率为84.44%,远高于传统CRI系统的44.06%总平均去除率。该研究成果为治理农村生活污水提供了一项行之有效的生态治理技术措施。     

化学除磷-水解酸化-厌氧接触-接触氧化工艺处理榨菜废水

榨菜废水的高含盐量和高氮磷对微生物有较强的抑制作用,处理难度大.以处理规模400 m3/d的重庆某榨菜厂废水处理工程为例,其进水COD 3 000～4 000 mg/L,BOD5 1445 mg/L,盐度1.5％～2.5％(以NaCl计),氨氮80～120 mg/L,总磷25～30 mg/L.通过驯化耐盐微生物为主体菌种,采用化学除磷-水解酸化-厌氧接触-接触氧化工艺进行处理,出水COD、BOD5、氨氮、总磷以及盐度平均分别为70.5 mg/L、14.9 mg/L、9.4 mg/L、0.46 mg/L以及1.53％,可以达到《污水综合排放标准》(GB8978-1996)一级标准.