Recycling of treated domestic effluent from an on-site wastewater treatment system for hydroponics.

An alternative method to conserve water and produce crops in arid regions is through hydroponics. Application of treated wastewater for hydroponics will help in stripping off nutrients from wastewater, maximising reuse through reduced evaporation losses, increasing control on quality of water and reducing risk of pathogen contamination. This study focuses on the efficiency of treated wastewater from an on-site aerobic wastewater treatment unit. The experiment aimed to investigate 1) nutrient reduction 2) microbial reduction and 3) growth rate of plants fed on wastewater compared to a commercial hydroponics medium. The study revealed that the chemical and microbial quality of wastewater after hydroponics was safe and satisfactory for irrigation and plant growth rate in wastewater hydroponics was similar to those grown in a commercial medium.     

Effective distribution of domestic wastewater effluent between percolation trenches in on-site treatment systems.

On-site treatment systems discharging to groundwater rely on the effective distribution of effluent across a percolation area to provide an appropriate loading rate for the subsoil. In Ireland, this is achieved in a distribution box which splits the effluent evenly between the requisite number of percolation pipes. The flow regime experienced at four different distribution boxes was monitored continuously over twelve month periods which established that the most common flow rates at the distribution unit were in the range 1-4 litres/minute for a four to five person dwelling. In addition, the average flow rate from the four sites was only 100 litres per person per day, compared to recommended design value of 180 litres per person per day. Two distribution boxes were also tested in the laboratory to assess their distribution efficiency over a range of loading rates. The most commonly installed unit was found to significantly favour two out of the four trenches and both units were shown to perform particularly poorly at a range of different off-level installation angles. Modifications to the boxes were also tested, involving plastic V-notch inserts which were shown to greatly improve the hydraulic distribution and make the unit much less sensitive to off-level installation or subsidence.     

Application of subsurface wastewater infiltration system to on-site treatment of domestic sewage under high hydraulic loading rate

In order to enhance the hydraulic loading rate(HLR) of a subsurface wastewater infiltration system(SWIS) used in treating domestic sewage,the intermittent operation mode was employed in the SWIS. The results show that the intermittent operation mode contributes to the improvement of the HLR and the pollutant removal rate. When the wetting-drying ratio(R WD) was 1.0, the pollutant removal rate increased by(13.6 ± 0.3)% for NH3-N,(20.7 ± 1.1)% for TN,(18.6 ± 0.4)% for TP,(12.2 ± 0.5)% for BOD,(10.1 ± 0.3)% for COD, and(36.2 ± 1.2)% for SS, compared with pollutant removal rates under the continuous operation mode. The pollutant removal rate declined with the increase of the HLR. The effluent quality met The Reuse of Urban Recycling Water e Water Quality Standard for Scenic Environment Use(GB/T 18921-2002)even when the HLR was as high as 10 cm/d. Hydraulic conductivity, oxidation reduction potential(ORP), the quantity of nitrifying bacteria, and the pollutant removal rate of NH3-N increased with the decrease of the R WD. For the pollutant removal rates of TP, BOD, and COD, there were no significant difference( p 0.05) under different R WD s. The suggested R WD was 1.0. Relative contribution of the pretreatment and SWIS to the pollutant removal was examined, and more than 80% removal of NH3-N, TN, TP, COD, and BOD occurred in the SWIS.     

高负荷好氧生物技术在生活污水回用中的应用研究

喷射式内循环反应器处理大庆东城区生活污水的试验结果表明,水力停留时间仅需0.5～1h,对COD去除率大于80％,对BOD的去除率高于85％,处理出水即可达标排放。试验中最高的容积负荷为10.91 kgCOD/(m~3·d),是常规活性污泥法处理生活污水的10倍。好氧条件下,喷射式内循环反应器具有除磷脱氮效果,对总氮的平均去除率高于50％,对总磷的去除率高于70％。与膜过滤联合的污水回用工艺试验结果表明,两种联合工艺均可满足生活杂用水水质标准,综合考虑运行费用和处理效果,联合工艺2更具优势。     

The development of a code of practice for single house on-site wastewater treatment in Ireland

The performance of six separate percolation areas was intensively monitored to ascertain the attenuation effects of unsaturated subsoils with respect to on-site wastewater effluent: three sites receiving septic tank effluent, the other three sites receiving secondary treated effluent. The development of a biomat across the percolation areas receiving secondary treated effluent was restricted on these sites compared to those sites receiving septic tank effluent. This created significant differences in terms of the hydraulic loading on the percolation areas with implications for the transport and attenuation of indicator microorganisms and nitrogen down through the subsoils and into the groundwater. The results of this work have formed a large input into the production of a new Code of Practice Wastewater Treatment and Disposal Systems Serving Single Houses. This has led to changes in the design of on-site hydraulic loading from 180 L per capita per day (L/c.d) down to 150 L/c.d. The range of acceptable subsoils receiving septic tank effluent has narrowed for more highly permeable subsoils following a series of tracer studies using bacteriophages. However, the range has been extended for lower permeability subsoils (range 0.08 down to 0.06 m/d) receiving secondary treated effluent in order to encourage the effluent to spread further along the trenches. The maximum individual length of percolation trenches receiving secondary effluent has also been reduced to 10 m to encourage dispersion on a wider area. This paper thus highlights how research can directly feed into a Code of Practice.     

Implications of effluent discharge from a proposed wastewater treatment plant on coastal water quality in the upper gulf of Thailand

Abstract

The paper deals with the assessment of the change in coastal water quality due to effluent discharge from a wastewater treatment plant through an outfall in the Upper Gulf of Thailand. A hydrodynamic and water quality modeling approach is used to predict the water quality level in the vicinity of the outfall when the effluent discharge and concentration levels are specified. With the continuation of effluent discharge for a one‐year period, the concentration levels of coliform bacteria and nutrients increase significantly in the vicinity of the outfall. These inferred states of seawater quality would pose hygiene risks for green mussel cultivation and affect the ecosystem due to high nutrient enrichment and eutrophication. Recommendations for improvement are put forward keeping a balance between social, economic, and engineering considerations.     

河北省入河排污口调查分析

根据调查监测资料对入河排污口分布情况、入河污水量、入河污染物量和入河污水水质进行分析评价，并与1990年调查资料进行对比分析，提出了其中存在问题和防治对策。     

Heavy metal removal from winery wastewater in the case of restrictive discharge regulation.

In most cases of winery effluent, the heavy metal content, especially zinc (Zn) and copper (Cu), does not meet the limits for the discharge as imposed by the most restrictive regulations at international level (0.4 mgCu/L and 1.0 mgZn/L in the Italian regulations). An alternative for the reduction of Cu and Zn is the on-site pre-treatment of wastewater at the winery in order to meet the limits for the discharge into the public sewerage. The purpose of this study is to evaluate the effectiveness of a pre-treatment based on chemical precipitation with chelating agents (TMT: 2,4,6-trimercaptotriazine), for the reduction of Cu and Zn from raw winery wastewater. The chemical precipitation was optimised at lab-scale through jar tests in order to evaluate the optimal dosages. An average dosage equal to 0.84 mL of TMT (15%) for 1 mg of Cu removed was estimated. Furthermore, the efficiency of the on-site chemical pre-treatment was investigated at pilot scale. The results confirmed the feasibility of using TMT treatment for the reduction of Cu and Zn in order to meet the limits for discharge into the sewerage. Contextually to the removal of heavy metals, the chemical pre-treatment allowed us to obtain the reduction of particulate COD and TSS. Finally, the costs for the operation and the management of the on-site pre-treatment were evaluated.     

Membrane bioreactor application in wastewater re-use from the effluent of Bali primary WWTP, northern Taiwan.

Two MBR pilot systems were constructed and tested in the Bali Primary WWTP. The pilot study shows that two MBR systems, i.e. the Green-MenBio system (MBR-1) and the Bio-MF system (MBR-2), can both fulfill the requirement of wastewater reclamation standard. The MBR-2 system is more economical compared with MBR-1 system. The cost of US dollars 0.10-0.16/m3 is estimated to reclaim the effluent of primary WWTP in Taiwan. The Bali Primary WWTP has the capacity of 1,320,000 cmd which is the biggest in Taiwan. The domestic wastewater of partial Taipei City and Taipei County are collected and transported to the Bali Primary WWTP. The effluent of the Bali Primary WWTP is then discharged into the ocean through two 3.8 m marine outfalls. The AO processes are installed in both MBR systems. More than 90% of the NH3-N can be removed through the AO and membrane processes. The outflow of the MBR systems (without RO) can reach the quality of COD <30 mg/l, BOD <10 mg/l, SS <5 mg/l, NH3-N <3 mg/L. The outflow of the MBR system is proposed to transport 40 km south to the Taoyuan County where four new industrial parks are to be constructed. Part of the reclaimed water is to be used on irrigation and another portion is to be sent to the industries after RO treatment.     

Reducing the total discharge from a large WWTP by separate treatment of primary effluent overflow.

At many large wastewater treatment plants (WWTPs) the increased hydraulic load, caused by combined sewer systems during storm events, results in primary effluent overflow when the capacity of further treatment is exceeded. Due to stringent effluent standards, regulating the total discharge from the WWTPs, the Rya WWTP in G?teborg and the Sj?lunda WWTP in Malm? will have to reduce the impact of primary effluent overflow. Separate, high rate, precipitation processes operated only during high flow conditions have been investigated in pilot units at the two WWTPs. Precipitation in existing primary settlers operated at a surface loading of 3.75 m/h removed phosphorus to 0.35 mg/l. The Actiflo process was also shown to remove suspended solids and phosphorus well. BOD was reduced by 50-60%. With such processes the overall effluent concentrations from the plants can be reduced significantly. Key upgrading features are small footprints, short start up time and high efficiency.     

Effects of hydraulic retention time,temperature, and effluent recycling on efficiency of anaerobic filter in treating rural domestic wastewater

With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time(HRT), temperature, and effluent recycling on the treatment efficiency of an anaerobic filter(AF) reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18℃, 21℃, and 24℃, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67℃, 30.57℃, and 26.91℃; and three effluent recycling ratios of 1:1, 1:2, and 2:1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for +4NH-N, 19% to 23% for 3NO-N-, and 12% to 22% for TP. In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for +4NH-N, 30% to 34% for 3NO-N-, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30℃, and an effluent recycling ratio of 2:1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling.     

Effects of effluent recirculation in vertical-flow constructed wetland on treatment efficiency of livestock wastewater.

Enhancing the treatment efficiency of livestock wastewater by effluent recirculation is investigated in a pilot-scale vertical-flow constructed wetland. The wetland system is composed of downflow and upflow stages, on which narrow-leaf Phragmites communis and common reed Phragmites typhia are planted, respectively; each stage has a dimension of 4 m(2) (2 m x 2 m). Wastewater from the facultative pond is fed into the system intermittently at a flow rate of 0.4 m(3)/d. Recirculation rates of 0, 25%, 50%0, 100% and 150% are adopted to evaluate the effect of the recirculation rate on pollutants removal. This shows that with effluent recirculation the average removal efficiencies of NH4-N, BOD5 and SS obviously increase to 61.7%, 81.3%, and 77.1%, respectively, in comparison with the values of 35.6%o, 50.2%, and 49.3% without effluent recirculation. But the improvement of TP removal is slight, only from 42.3% to 48.9%. The variations of NH4-N, DO and oxidation-reduction potential (ORP) of inflow and outflow reveal that the adoption of effluent recirculation is beneficial to the formation of oxide environment in wetland. The exponential relationships with excellent correlation coefficients (R(2) > 0.93) are found between the removal rates of NH4-N and BOD5 and the recirculation rates. With recirculation the pH value of the outflow decreases as the alkalinity is consumed by the gradually enhanced nitrification process. When recirculation rate is kept constant at 100%, the ambient temperature appears to affect NH4-N removal, but does not have significant influence on BOD5 removal.     

重庆金佛山地下水的氮污染源研究

为了研究重庆金佛山地区地下水的氮污染情况,于2007年7月采集21个水样,利用阴离子色谱仪和ICP-OES分析主要阴、阳离子,再利用EA-Conflo-IRMS联机测试δ15N-NO3-,分析得知:金佛山地区地下水已经受到NO3--N的威胁,尤其是Group1,污染严重;判断地下水的主要氮污染源有粪肥、化肥、天然土壤、工业废弃物和生活污水等,初步得出该区δ15N的变化范围,为以后深入研究金佛山地区地下水质提供基础。这一研究对金佛山部分村镇居民寻找和饮用地下水具有一定的指导意义。     

Predicting fate of the contraceptive pill in wastewater treatment and discharge.

The risk of endocrine disrupters to humans and wildlife is to date poorly understood, although evidence of effects is now widespread. In understanding the risk, an important step is the determination of the partitioning, as well as chemical and biochemical transformation, of compounds in the environment, the water cycle and the food chain. This is a complex task and this paper is a first step towards estimating some of these factors from a largely theoretical approach. A chemical fate model is used to predict the fate of the contraceptive drug 17alpha-ethinylestradiol (EE2). The example of the contraceptive pill is chosen to follow the journey of the drug from human ingestion and excretion to treatment in a sewage treatment plant (STP) using fugacity-based fate models, followed by discharge into a receiving river and eventually into the estuary/sea. The model predicts how EE2 will partition into the different compartments during each stage of this journey and thereby infiltrate into the food chain. The results suggest that a person would have to ingest more than 30,000 portions of fish to consume an equivalent to a single average dose of the contraceptive pill. While this scenario is highly unlikely, the biochemical consequence of the contraceptive pill is greatly significant. Furthermore, there are many identified similarly estrogenic compounds in the environment while this study only considers one. Cumulative effects of such compounds as well as degradation into other potent compounds may be anticipated. An important message in this paper is the interrelation of wastewater effluent discharge and eventual human exposure of marginally degradable and lipophilic chemicals. While at present the main concerns regarding endocrine disrupters appear to be the fear of their occurrence in drinking water sources, it is clear that the domains of wastewater treatment and discharge, water supply and contamination of food should not be treated as separate issues. The model suggests that exposure from food (contaminated by effluent) may be much more significant than from drinking water.     

A PCR-DGGE approach to evaluate the impact of wastewater source on the antibiotic resistance diversity in treated wastewater effluent

Increased incidence of antibiotics in human-affected environments is raising concerns about increase in acquired antibiotic resistance by environmental bacteria. Wastewater collection and treatment systems are likely significant anthropogenic sinks and vectors for antibiotics and associated antibiotic resistance. Typical municipal treatment plants collect wastewaters of various sources, including well-established antibiotic resistance reservoirs such as hospitals, intensive care units and nursing homes, and integrate them with sources not commonly identified as major sources of antibiotic resistance, such as residential or industrial sources. A comprehensive PCR-DGGE diversity analysis of wastewater antibiotic-resistant bacteria was performed to evaluate the role of various wastewater sources in the discharge of antibiotic resistance by a municipal treatment plant. Wastewater sources are clearly inducing resistance in the final effluent but the role of each source type is highly variable, likely as a function of variable environmental conditions or water use patterns. Comparisons between primary treatment and secondary treatment stages indicate a strong role of the intensity of the wastewater treatment in the diversity profiles of antibiotic-resistant bacteria. While pervasiveness of antibiotic resistance in the system impedes clear discrimination between sources in the tested system, there are indications of specific source type related impacts.     

Investigation on the behaviour of selected pharmaceuticals in the groundwater after infiltration of treated wastewater.

In a rural arid area without suitable receiving water the treated wastewater of a low loaded municipal wastewater treatment plant with full nutrient removal and additional post treatment steps is infiltrated into the unsaturated soil for groundwater recharge. Groundwater probes at increasing distances from the infiltration point have been sampled every two months over a period of 14 months. Beside conventional parameters (nutrients, carbon, and bacterial counts) samples were analysed for pharmaceutically active substances. Depending on and corresponding to their chemical structure and their fate during wastewater treatment, the selected substances showed different behaviour in the saturated zone of the groundwater. The antiepileptic Carbamazepine behaves very conservative and only is removed negligible even after long flow times within the subsurface zone. For other substances like the tranquilizer Diazepam or the analgesics Diclofenac a partial elimination during the different steps of wastewater treatment can be observed. Further degradation could be observed during the subsequent subsurface passage. In correlation with flow time additional removal of these substances from the aqueous phase can be observed. The musk substances Galaxolide and Tonalide were removed to some extend but not as good as the previous mentioned compounds.     

改性粉煤灰处理含磷生活污水试验

为了防止水体富营养化和有效处理生活污水,以改性粉煤灰为吸附剂,对含磷生活污水进行吸附脱磷试验,并研究粉煤灰粒径、投加量、pH值、温度、振荡强度以及吸附时间等因素对脱磷效果的影响。结果表明:在粉煤灰粒径为160~200目、投加量为25 g/L、溶液pH值为3.5、水温为50℃的条件下,对磷质量浓度为6.8 mg/L的生活污水,以140 r/min的强度振荡吸附150 min,磷的去除率可高达95.3%,水样中的磷质量浓度降至0.5 mg/L以下。     

The effect of colloid stability of wastewater treatment plants effluent on nanofiltration performance.

Laboratory-scale filtration tests utilizing wastewater treatment plants (WWTP) effluent were conducted to investigate fouling and filtration behaviour, especially the influence of colloidal stability on nanofiltration performance. Acidification and coagulant dosage were used to create unstable colloidal conditions. Colloidal stability of the effluent was analysed on by zeta potential measurements. A statistical design method, full factorial design with blocking, has been used to account for effluent composition variations and to account for interaction between experimental parameters. The results show a high correlation between unstable colloidal natural organic matter and the formation of dense fouling layers. The reversibility of the fouling process was shown to be independent from colloidal stability. Irreversible fouling was show to be promoted by mild acidic (pH 5) effluent conditions, whereas coagulant addition showed an increase in the reversibility of the fouling.     

Quantification of dissolved methane in UASB reactors treating domestic wastewater under different operating conditions

This paper aimed at measuring the concentration of methane dissolved in effluents from different UASB reactors (pilot-, demo- and full-scale) treating domestic wastewater, in order to calculate the degree of saturation of such greenhouse gas and evaluate the losses of energetic potential in such systems. The results showed that methane saturation degrees, calculated according to Henry's law, varied from ～1.4 to 1.7 in the different reactors, indicating that methane was oversaturated in the liquid phase. The overall results indicated that the losses of dissolved methane in the anaerobic effluents were considerably high, varying from 36 to 41% of total methane generated in the reactor. These results show that there is considerable uncontrolled loss of methane in anaerobic wastewater treatment plants, implying the need of research on technologies aimed at recovering such energetic greenhouse gas.