Removal of dissolved nitrogen, phosphorus and carbon from stormwater by biofiltration mesocosms.

Biofiltration systems are becoming a popular stormwater treatment device in water sensitive urban design for the removal of fine particulate and dissolved pollutants from stormwater. However, there is limited published data on the effectiveness of these systems for nutrient removal. We constructed biofiltration mesocosms to assess nutrient removal (nitrogen, phosphorus and carbon) under experimental conditions. Different types of media were compared (gravel, sand, and sandy-loam) in vegetated and non-vegetated mesocosms (six treatments in total). Five plant species were used. Vegetated sand and vegetated sandy-loam provided the best overall treatment. Vegetated mesocosms were very effective in removing nitrogen (63-77% removal) and phosphorus (85-94% removal) from synthetic stormwater, and removed substantially more nutrients than the non-vegetated treatments. All treatments removed a substantial portion of the carbon from the stormwater (28-66%). When flushed with tap water, nitrogen and phosphorus were retained by the vegetated mesocosms, but leached from the non-vegetated mesocosms. Plant growth was most vigorous in the sandy-loam media, indicating that this is a good growth media, even without the addition of organic matter.     

Textile effluent treatment in a UASB reactor followed by submerged aerated biofiltration

An upflow anaerobic sludge bed (UASB)-submerged aerated biofilter (SAB) system that treats effluents from a jeans factory was evaluated. The 210-day operational period was divided into three phases (PI, PII and PIII), each with a different hydraulic retention time (HRT in h) and organic loading rate (OLR in kg COD/m3.d). In PI, the best performance was achieved using the UASB (HRT 24, OLR 1.3) with COD and color removal efficiencies of 59 and 64%, respectively; the corresponding values were 77 and 86% for the final effluent. In PII, the efficiencies were 50 and 55% using the UASB (HRT 16, OLR 1.2), respectively, and 69 and 81% for the final system effluent, respectively. In PIII, the UASB (HRT 12 and ORL 3.2) showed the poorest performance; the efficiencies decreased to 48 and 50%, respectively. The same phenomenon occurred in the system with corresponding efficiencies decreasing to 69 and 61%. Throughout the experiment, the system removal efficiencies were between 57 and 88% for nitrogen and between 14 and 63% for sulfate. The final effluent showed relatively non-toxicity or moderate toxicity using Daphnia magna as an indicator. Therefore, the overall results showed that the use of a sequential anaerobic-aerobic system is promising for treatment of textile industrial wastewater.     

余姚市河网平枯水期水质模拟研究

MIKE11是一款功能强大的水流水质的计算软件,利用该软件对余姚市河网的平枯水期水质进行了模拟。对余姚市的河网概况、河网水动力基本方程和水质方程、河网水动力水质模型的建模、模型率定及验证作了介绍。验证结果表明,计算值和实测值吻合良好,相关指标的验证精度较高。     

Removal of cyanobacterial metabolites through wastewater treatment plant filters

Wastewaters have the potential to proliferate excessive numbers of cyanobacteria due to high nutrient levels. This could translate to the production of metabolites, such as the saxitoxins, geosmin and 2-methylisoborneol (MIB), which can impair the quality of wastewater destined for re-use. Biological sand filtration was assessed for its ability to remove these metabolites from a wastewater. Results indicated that the sand filter was incapable of effectively removing the saxitoxins and in some instances, the effluent of the sand filter displayed greater toxicity than the influent. Conversely, the sand filter was able to effectively remove geosmin and MIB, with removal attributed to biodegradation. Granular activated carbon was employed as an alternative filter medium to remove the saxitoxins. Results showed similar removals to previous drinking water studies, where efficient removals were initially observed, followed by a decrease in the removal; a consequence of the presence of competing organics which reduced adsorption of the saxitoxins.     

Municipal wastewater treatment by biofiltration: comparisons of various treatment layouts. Part 1: assessment of carbon and nitrogen removal

One of the largest wastewater treatment plants in the Paris conurbation (240,000 m(3)/d) has been studied over several years in order to provide technical and economical information about biological treatment by biofiltration. Biofiltration systems are processes in which carbon and nitrogen pollution of wastewater are treated by ascendant flow through immersed fixed cultures. This paper, focused on technical information, aims: (1) to compare performances of the three biological treatment layouts currently used in biofiltration systems: upstream denitrification (UD), downstream denitrification (DD) and combined upstream-downstream denitrification (U-DD) layouts; and (2) to describe in detail each treatment step. Our study has shown that more than 90% of the carbon and ammoniacal pollution is removed during biological treatment, whatever the layout used. Nitrate, produced during nitrification, is then reduced to atmospheric nitrogen. This reduction is more extensive when the denitrification stage occurs downstream from the treatment (DD layout with methanol addition), whereas it is only partial when it is inserted upstream from the treatment (UD layout - use of endogenous carbonaceous substrate). So, the UD layout leads to a nitrate concentration that exceeds the regulatory threshold in the effluent, and the treatment must be supplemented with a post-denitrification step (U-DD layout). Our work has also shown that the optimal ammonium-loading rate is about 1.1-1.2 kg N-NH(4)(+) per m(3) media (polystyrene) and day. For denitrification, the optimal nitrate-loading rate is about 2.5 kg N per m(3) media (expanded clay) and day in the case of DD with methanol, and is about 0.25 kg N-NO(3)(-) per m(3) media and day in the case of UD with exogenous carbonaceous substrate.     

不同覆膜方式与覆膜时期对旱地玉米的影响

试验观测了不同覆膜方式与覆膜时期对土壤水分、温度、旱地玉米生育期、生物学性状、产量及水分利用效率、经济效益的影响.经分析得出,全膜覆盖优于半膜覆盖,早覆膜优于晚覆膜.该地区玉米的最佳栽培方式为在扩大推广全膜双垄沟播秋季覆膜的基础上,进行全膜双垄沟播早春揭膜.     

Impact assessment of odours emitted by a wastewater treatment plant

Complaints from the Domingos Martins population about sewage odours in the city made the district attorney order an impact assessment of the odours emitted by the city wastewater treatment plant (WWTP). This study comprised various techniques, models and population surveys. In 2007, an odour emission model proved that the main hydrogen sulphide emitter was the aeration tank of the WWTP (13.5 g h(-1)) and such emissions, according to CALPUFF model, should be perceived in the whole Domingos Martins city centre area. In this area, 58% of those interviewed were annoyed by the WWTP odours. However, in 2009, the odour monitoring panel recorded few odour occurrences. A second population survey showed that hereafter only 20% of those interviewed were annoyed by the WWTP emissions. Odour emission and dispersion models run with 2010 data proved a drastic reduction of the WWTP aeration tank emissions and consequently the city centre was not bothered by WWTP emissions anymore. The odour emission reduction was due to the modification of the WWTP aeration tank system. Despite the odour emission reduction, houses located southeast of the WWTP were still annoyed by sewage odours. However, in this part of the town, other sources of sewage odours have been found.     

武汉南湖周边某雨水处理厂设计

南湖是武汉市第三大城中湖,水域面积约7.48 km2,现状水质为劣V类.武汉市于2019年启动南湖水环境提升工程,雨水处理厂是其中的重要子项之一.雨水处理厂服务汇水面积37.44 km2,控制目标为八大雨水排口全年开闸次数控制在10次以内,TSS总控制率≥75％,COD总控制率≥80％.初雨厂设计规模25万m3/d,采...     

Pre-treating algae-laden raw water by silver carp during Microcystis-dominated and non-Microcystis-dominated periods

Performance of pre-treating algae-laden raw water by silver carp during a non-Microcystis-dominated period (period I) and a Microcystis-dominated period (period II) was investigated in terms of algae cell concentration, total phosphorus content, chlorophyll a and phytoplankton species structure. During period I the ineffective filter-feeding for small green algae resulted in the increase of small single algae, which led to the negative removal of chlorophyll a, and when the biomass was higher, the negative was more significant. However, due to the effective filter-feeding of silver carp for Microcystis flos-aquae, the average removal efficiency exceeded 50% at all stocking biomass levels (20-120 g/m(3)) used in experiments during period II. Total phosphorus removal efficiencies could exceed 50% at silver carp biomass stocking levels of 60-80 g/m(3) during both period I and period II. The experimental results indicated that silver carp stocking contributed to the removal of colony-forming cyanobacteria, but led to the increase of single-cell algae (mainly green algae and diatoms) during both period I and period II. The initial phytoplankton community structure and the control of nutrient level were important factors in the choice of silver carp stocking biomass when used to purify algae-loaded water.     

Removal efficiency of 66 pharmaceuticals during wastewater treatment process in Japan.

Both biological treatment processes including conventional activated sludge (CAS) and biological nutrient removal (BNR) processes, and physico-chemical treatment processes including ozonation process and Title 22 process consisting of coagulation, sedimentation and filtration followed by UV or chlorination disinfection after the above biological processes, were compared from the viewpoint of removal efficiency. 66 pharmaceuticals including antibiotics, analgesics, psychoneurotic agents were measured with SPE-LC/MS/MS. 26 compounds out of 66 were detected in the influent ranging ng/L to microg/L order. Particularly, disopyramide, sulpiride, and dipyridamole that have been rarely detected before in the WWTP, occurred at concentration levels of more than 100 ng/L. The total concentration of the individual pharmaceuticals in the influent was efficiently removed by 80% during the biological treatment. But removal efficiencies of carbamazepine and crotamiton were less than 30%. The total concentration of the individual pharmaceuticals in the effluent from CAS process was 1.5 times higher than that from BNR process. Further, the total concentration of the individual pharmaceuticals in the discharge from WWTPs applying ozonation following activated sludge process was reduced to less than 20%. Physico-chemical treatment train called Title 22 treatment after CAS could not efficiently remove the pharmaceuticals. However, ozonation process followed by biological activated carbon process could efficiently reduce all the residual pharmaceuticals below their quantification limits.     

Municipal wastewater treatment by biofiltration: comparisons of various treatment layouts. Part 2: assessment of the operating costs in optimal conditions

This work aims to compare the operation costs (energy, reagents, waste management) for the three layouts usually used in wastewater treatment plants incorporating biofilters, using technical and economical data acquired during 10 years of operation of a Parisian plant (Seine Centre, 240,000 m(3) d(-1) -800,000 equivalent inhabitants). The final objective is to establish general economical data and tendencies that can be translated from our study to any biofiltration plant. Our results evidenced the savings achieved through the treatment process combining upstream and downstream denitrification. To use this layout reduced the operating costs by some 10% as compared with conventional processing only comprising downstream denitrification. Operating costs were respectively estimated at 37 and 34 €/1,000 m(3) for downstream denitrification and combining upstream and downstream denitrification layouts.     

Removal of cyanobacteria, cyanotoxins, heterotrophic bacteria and endotoxins at an operating surface water treatment plant.

The removal of cyanobacteria, hepatotoxins produced by them (microcystins), phytoplankton, heterotrophic bacteria and endotoxins were monitored at a surface water treatment plant with coagulation, clarification, sand filtration, ozonation, slow sand filtration and chlorination as the treatment process. Coagulation-sand filtration reduced microcystins by 1.2-2.4, and endotoxins by 0.72-2.01 log10 units. Ozonation effectively removed the residual microcystins. The treatment process reduced phytoplankton biomass by 2.2-4.6 and heterotrophic bacteria by 2.0-5.0 log10 units. In treated water, the concentration of microcystins never exceeded the WHO guide value (1 microg/L), but picoplankton and monad cells were often detected in high numbers. The heterotrophic bacterial isolates from the treated waters belonged to genera Sphingomonas, Pseudomonas, Bacillus, Herbaspirillum and Bosea.     

Bioassessment of wet-weather pollution impacts on fine sediments in urban waters by benthic indices and the sediment quality triad.

Benthic invertebrate assessments can be used to gauge the impact of urban wet-weather flows in receiving waters. Experiences from Cemagref in France have shown that standardized benthic indices (e.g. Oligochaete Index of Sediment Bioindication - IOBS) can be used to reliably determine the ecological status of urban streams and can be incorporated into the new European Water Framework Directive. The Canadian studies on streams and stormwater ponds using chemical analyses, benthic toxicity testing and benthic invertebrate community structure (i.e. the sediment quality triad) comparisons have shown that toxicity was more likely to occur in ponds at sites with higher concentrations of heavy metals and heavier polycyclic aromatic hydrocarbons, and at greater water depths, where fine sediments from urban runoff accumulated. A more comprehensive evaluation of wet-weather flow impacts could be obtained by combining approaches from both countries.     

Removal of endocrine-disrupting chemicals by ozonation in sewage treatment.

Treatment experiments by two laboratory scale semi-batch reactors and a demonstration scale process were both carried out to evaluate endocrine disrupting chemical removal characteristics by ozonation in sewage treatment. In the semi-batch mode experiments, secondary effluent and primary effluen of sewage treatment plants were ozonated respectively. Behaviour of brominated by-products was also evaluated. The results based on these studies indicated that estrogenicity in wastewater can be removed by ozonation effectively. The condition of ozonation until dissolved ozone concentration increased to 0.1 mg/L, which corresponded to 1 mgO3/mgC and 0.4 mgO3/mgC of ozone consumption per initial DOC for secondary effluent and primary effluent, respectively, is proposed as an appropriate operational condition for efficient removal of EDCs as well as UV254 and SUVA without production of brominated by-products.     

冰情影响河段测流方法研究

正确确定河道流量对于研究寒冷地区冬季河渠道的冰情具有重要意义．对于渠底坡度一定的冰情影响河道,即使流量一定,流动阻力增加引起水深增加,导致敞流期量测得到的水位～流量关系改变,需要重新考虑测流垂线上测点选择．为了减少量测时间、成本及恶劣天气条件下工作不便,通常并不细测垂线流速分布,而只施测少数几个点,同时利用垂向测点流速和平均流速之间关系估计平均流速．测点选择不当往往造成很大误差．本文在传统二点测流法基础上,推导得到用于确定垂线平均流速的任意二点测流法,并应用原型观测资料进行了验证。     

Removal mechanisms of endocrine disrupting compounds (steroids) during soil aquifer treatment.

The objective of this study was to determine the primary removal mechanisms of endocrine disruptors such as steroidal hormones present in reclaimed water, specifically 17beta-estradiol, estriol, and testosterone, during groundwater recharge via soil aquifer treatment (SAT). Steroidal hormones were quantified using enzyme-linked immunosorbent assays. Bench-scale studies and laboratory-scale soil column experiments were employed to determine what mechanisms (i.e., adsorption, biodegradation, photolytic degradation) dominate the removal of the three compounds of interest during SAT. Findings of these studies revealed that the dominating removal mechanism for the compounds of interest during SAT is adsorption to the porous media matrix and additional attenuation to below the detection limit occurred in the presence of bioactivity. This additional removal occurred regardless of dominating redox conditions (aerobic vs. anoxic) or the type of organic carbon matrix present (hydrophobic acids, hydrophilic carbon vs. colloidal carbon).     

Removal of micropollutants in municipal wastewater treatment plants by powder-activated carbon

Micropollutants (MP) are only partly removed from municipal wastewater by nutrient removal plants and are seen increasingly as a threat to aquatic ecosystems and to the safety of drinking water resources. The addition of powder activated carbon (PAC) is a promising technology to complement municipal nutrient removal plants in order to achieve a significant reduction of MPs and ecotoxicity in receiving waters. This paper presents the salient outcomes of pilot- and full-scale applications of PAC addition in different flow schemes for micropollutant removal in municipal wastewater treatment plants (WWTPs). The sorption efficiency of PAC is reduced with increasing dissolved organic carbon (DOC). Adequate treatment of secondary effluent with 5-10 g DOC m(-3) requires 10-20 g PAC m(-3) of effluent. Counter-current use of PAC by recycling waste PAC from post-treatment in a contact tank with an additional clarifier to the biology tank improved the overall MP removal by 10 to 50% compared with effluent PAC application alone. A dosage of 15 g PAC m(-3) to a full-scale flocculation sand filtration system and recycling the backwash water to the biology tank showed similar MP elimination. Due to an adequate mixing regime and the addition of adapted flocculants, a good retention of the fine fraction of the PAC in the deep-bed filter were observed (1-3 g TSS m(-3); TSS: total suspended solids). With double use of PAC, only half of the PAC was required to reach MP removal efficiencies similar to the direct single dosage of PAC to the biology tank. Overall, the application of PAC in WWTPs seems to be an adequate and feasible technology for efficient MP elimination (>80%) from wastewater comparable with post ozonation.     

Removal of selected pharmaceuticals by chlorination, coagulation-sedimentation and powdered activated carbon treatment

Removal property of nine pharmaceuticals (clofibric acid, diclofenac, fenoprofen, gemfibrozil, ibuprofen, indomethacin, ketoprofen, naproxen and propyphenazone) by chlorination, coagulation-sedimentation and powdered activated carbon treatment was examined by laboratory-scale experiments under the conditions close to actual drinking water treatment processes. Indomethacin and propyphenazone were completely degraded by chlorination within 30 minutes, but others remained around 30% (naproxen and diclofenac) or more than 80% of the initial concentration after 24 hours. A couple of unidentified peaks in a chromatogram of the chlorinated samples suggested the formation of unknown chlorination by-products. Competitive adsorption was observed when the mixed solution of the target pharmaceuticals was subjected to batch adsorption test with powdered activated carbon. Clofibric acid and ibuprofen, which were relatively less hydrophobic among the nine compounds, persisted around 60% of the initial concentration after 3 hours of contact time. Removal performance in actual drinking water treatment would become lower due to existence of other competitive substances in raw water (e.g. natural organic matter). Coagulation-sedimentation using polyaluminium chloride hardly removed most of the pharmaceuticals even under its optimal dose for turbidity removal. It is suggested that the most part of pharmaceuticals in raw water might persist in the course of conventional drinking water treatments.     

鱼类产卵敏感期河流生态流速的分区分类阈值研究

敏感生态流量目标的合理制定是生态流量管理的重难点问题。针对目前敏感生态流量目标制定中存在的计算方法繁杂、关键参数缺乏等问题,本文以鱼类产卵期为重点,提出了分区分类河流敏感期生态流速和生态流量核算方法,制定了不同区域(东北、黄淮海、西南、长江中下游和东南沿海)、不同类型(按集水面积、山区河段和平原河段等划分)河流敏感期生态流速阈值。结果显示,全部分区分类推荐流速平均值为0.66 m/s,其中山区大站平均值为0.94 m/s、山区小站平均值为0.62 m/s、平原大站平均值为0.63 m/s、平原小站平均值为0.46 m/s。基于阈值核算了全国217个鱼类产卵生境保护河段的敏感期生态流量目标,并结合部分断面湿周法结果对阈值合理性与适应性进行了验证,验证结果表明相关阈值和方法适应于不同类型、不同规模河流,可为我国现阶段河流敏感生态流量管控提供参考。     

Model for reservoir operations during periods of high flow

A combined dynamic programming optimization and hydraulic simulation model is presented for the analysis of the operation of hydroelectric reservoir facilities during periods of flood flows. The model is specifically designed to analyze the impacts of reservoir operations on upstream flooding and to consider complex reservoir outlet works. The model was applied to analyze the design and operational strategies for the Visegrad Hydroelectric Project in Yugoslavia. Results of the analysis indicated that the most economical means of flood protection for upstream areas was a combination of flood protection structures and a lowering of the reservoir storage level in anticipation of flood flows.