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1.
Effluents from aquaculture facilities vary between species and among production systems. Drainage ditches commonly convey effluents from central Arkansas baitfish ponds. Ditches could potentially reduce suspended solids prior to effluent release into receiving streams through settling. We characterized suspended solids in effluents from baitfish ponds and evaluated changes in suspended solids in drainage ditches. We also characterized drainage ditches based on width, depth, slope, and percent vegetation cover. Average (± SD) total suspended solids (TSS) at the point of discharge was 52 (± 41) mg/L, while volatile suspended solids (VSS) averaged 22 (± 23) mg/L. Screening effluents did little to alter their composition. Approximately 76% of TSS were less than 5 μm. There were no significant changes in effluent solids along drainage ditches 100 m from the point of discharge and no significant correlations between ditch characteristics and changes in either TSS or VSS. Existing ditches are quite variable and are not necessarily effective in removing solids present in baitfish effluents. Screening and use of ditches as settling basins seem impractical for effluent treatment given the characteristics of solids in baitfish effluents.  相似文献   

2.
An environmental assessment was made of Alabama channel catfish Ictalurus punctatus farming which is concentrated in the west‐central region of the state. There are about 10,000 ha of production ponds with 10.7% of the area for fry and fingerlings and 89.3% for food fish. Food fish production was about 40,800 tons in 1997. Watershed ponds filled by rainfall and runoff make up 76% of total pond area. Water levels in many of these ponds are maintained in dry weather with well water. The other ponds are embankment ponds supplied by well water. Harvest is primarily by seine‐through procedures and ponds are not drained frequently. The main points related to Alabama catfish farming and environment issues are as follows: 1) catfish farming in Alabama is conservative of water, and excluding storm overflow, about two pond volumes are intentionally discharged from each pond in 15 yr; 2) overflow from ponds following rains occurs mostly in winter and early spring when pond water quality is good and stream discharge volume is high; 3) total suspended solids concentrations in pond effluents were high, and the main sources of total suspended solids were erosion of embankments, pond bottoms, and discharge ditches; 4) concentrations of nitrogen and phosphorus in effluents were not high, but annual effluent loads of these two nutrients were greater than for typical row crops in Alabama; 5) ground water use by the industry is about 86,000 m3/d, but seepage from ponds returns water to aquifers; 6) there is little use of medicated feeds; 7) copper sulfate is used to control blue‐green algae and off‐flavor in ponds, but copper is rapidly lost from pond water; 8) although sodium chloride is applied to ponds to control nitrite toxicity, stream or ground water salinization has not resulted from this practice; 9) fertilizers are applied two or three times annually to fry and fingerling ponds and occasionally to grow‐out ponds; 10) hydrated lime is applied occasionally at 50 to 100 kg/ha but this does not cause high pH in pond waters or effluents; 11) accumulated sediment removed from pond bottoms is used to repair embankments and not discarded outside ponds; 12) sampling above and below catfish pond outfalls on eight streams revealed few differences in stream water quality; 13) electricity used for pumping water and mechanical aeration is only 0.90 kW h/kg of production; 14) each metric ton of fish meal used in feeds yields about 10 tons of dressed catfish. Reduction in effluent volume through water reuse and effluent treatment in settling basins or wetlands does not appear feasible on most farms. However, some management practices are recommended for reducing the volume and improving the quality of channel catfish pond effluents.  相似文献   

3.
This study was conducted to help provide a framework for Australian regulation of shrimp farm siting and discharges. Monitoring of farm water usage, and intake and discharge water quality was conducted at three commercial intensive shrimp farms, chosen to represent different operating environments, latitudes, cultured species and management styles. Weekly samples were taken over 3 years, for 3–12 months at each farm, to investigate intake and discharge concentrations and loads of total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP). Mean water exchange was 1.4 ML ha?1 day?1 (about 10% day?1) at the first farm studied and 0.5 ML ha?1 day?1 (about 3.6% day?1) at the others. Farm mean discharge concentration varied as follows: TSS, from 36.9 to 119 mg L?1; TN, from 2.1 to 3.1 mg L?1 and TP, from 0.22 to 0.28 mg L?1. Farm mean intake concentrations were from 11% to 91% of equivalent mean discharge concentration (for TN at Farm B and TSS at Farm C respectively). Mean net discharge loads, related to area of production ponds at each farm, varied as follows: TSS, from 4.8 to 85.7 kg ha?1 day?1; TN, from 1 to 1.8 kg ha?1 day?1 and TP, from 0.11 to 0.22 kg ha?1 day?1. The highest net loads of TSS, TN and TP were all from the farm with the highest water exchange rate, located on a coastal river, and studied during a year of high rainfall with associated poor water quality. These results can be used to help predict likely discharge characteristics for new shrimp farms, and provide a benchmark against which to evaluate future improvements in shrimp farm environmental management.  相似文献   

4.
A generalized nitrogen budget was constructed to evaluate the potential role of mangrove sediments as a sink for dissolved inorganic nitrogen (DIN) in shrimp pond effluents. DIN concentrations were measured in pond effluents from three semi-intensive shrimp ponds along the Caribbean coast of Colombia between 1994–1995. Mean NH4+ concentrations in the discharge water for all farms were significantly higher (67 × 12 μg/L) than in the adjacent estuaries (33 × 8 μg/L). Average NH4+ concentrations in the pond discharge over all growout cycles were similar, representing an approximate doubling in relation to estuarine water concentrations. In contrast, NO2-+ NO3- concentrations were similar in both pond effluent and estuarine waters. Dissolved inorganic nitrogen loading of the ponds was similar. The estimated reduction of DIN in pond effluents by preliminary diversion of outflow to mangrove wetlands rather than directly to estuarine waters would be × 190 mg N/m2 per d. Based on this nitrogen loss and depending upon the enrichment rate, between 0.04 to 0.12 ha of mangrove forest is required to completely remove the DIN load from effluents produced by a 1-ha pond.  相似文献   

5.
This study examined the effects of different hydraulic loading rates on the treatment efficiency of subsurface flow (SSF) constructed wetlands treating effluents from trout farming over a period of 6 months. Six identical wetland cells with a pre-sedimentation zone of 9.6 m2 and a root zone of 23.6 m2 were loaded with effluents from intensive trout farming (> 2.1 kg feeding stuff per L/s and day). The total runoff of 13.2 L/s was treated in the wetland cells, where two duplicate cells received equal hydraulic loads of 3.9, 1.8 and 0.9 L/s. All examined wetland cells had significant treatment effects on the nutrient fractions containing particulate matter [total nitrogen (TN), total phosphorous (TP), biological oxygen demand in 5 days (BOD5), chemical oxygen demand (COD), and total suspended solids (TSS)].

Efficiency was between 5.5% for TN and 90.1% for TSS. The SSF wetland also had a high treatment effect on total ammonia nitrogen (TAN), with efficiencies of 61.2 to 87.8%. Nitrate nitrogen (NO3–N) and phosphate phosphorous (PO4–P) showed a significant increase in the wetland effluent by 8.4 to 209%. Nitrite nitrogen (NO2–N), had no significant, or significant effluent increase depending on the inflow rate. Treatment efficiency for particulate nutrients and TAN increased with decreasing hydraulic load, while the differences between 1.8 and 0.9 L/s were not significant. The treatment efficiency for TP was constant for all cells, at around 40%. The wetland receiving 3.9 L/s was over-flooded after 10 to 12 weeks due to colmatation. Nevertheless, the wetland still showed high treatment efficiencies. For commercial trout farms, SSF wetlands are a highly effective method of effluent treatment. A hydraulic load of 1 L/s on 13.3 m2 wetland area (1.8 L/s on the examined wetland) seems most suitable. Higher loads lead to accelerated wetland colmatation, while lower loads waste space.  相似文献   


6.
The focus of this article is the post-harvest treatment of effluent from hybrid striped bass (HSB) pond aquaculture to meet effluent discharge standards for Biochemical Oxygen Demand (BOD; 5 mg/L) and chlorophyll-α (40 μg/L) established by the North Carolina Division of Water Quality (DWQ). The specific application is to HSB pond aquaculture in Aurora, North Carolina. A variety of effluent treatment options were proposed and evaluated based on their efficacy in reaching the new standards on a 28.8-ha (72-acre) HSB farm. The economic feasibility of the proposed options ranged from positive $499 to negative $121,691 using the partial budget methodology. Our results indicate that retaining water on-farm for subsequent production cycles instead of discharging had the highest positive impact ($499) on annual farm budgets and may reduce production costs without compromising fish yields. Application of effluents onto existing or newly planted trees was also an attractive alternative because of the possible generation of additional income and the conversion of a point source discharge into a non-point discharge. By conversion of a point source into a non-point source the pond effluents would also benefit from the additional biological treatment and filtration of the effluents by the trees and the associated soil organisms.  相似文献   

7.
张玉平  刘金金  张芬 《中国水产科学》2020,27(12):1448-1463
为综合评估上海地区池塘沉积物环境质量状况,2016-2019年对上海地区36个养殖场池塘采集沉积物样品360个,检测和分析沉积物中总氮（TN）、总磷（TP）、总有机碳（TOC）及重金属Cu、Zn、Pb、Cd、Cr、Hg和As含量。研究结果表明,池塘0~10 cm层和10~20 cm层沉积物中TN、TP、TOC及各重金属均值分布无显著差异（P>0.05）,0~20 cm层沉积物（干重）中TN、TP和TOC平均含量分别为（873.37±352.45）mg/kg、（685.66±199.66）mg/kg和（6.62±3.05）mg/g,三者相关性显著。综合污染指数法和有机指数法评价结果表明,池塘沉积物中氮和有机物质的累积量较低,磷累积量相对较高,均低于其他地区高产池塘。池塘沉积物中Cr、Cd、Cu和Hg样品超标率分别为6.42%、3.21%、4.13%和1.38%,Zn、Pb和As无超标现象。地质累积指数、潜在生态危害指数法和一致性沉积物质量基准评价结果表明,上海地区池塘沉积物中重金属整体上处于清洁等级、低潜在生态危害状态,预测不会引发生物毒性效应。  相似文献   

8.
菱角对农村富营养化水体营养盐吸收的初步研究   总被引：2，自引：0，他引：2  
为探究浮叶植物对农村富营养化废水中营养盐的去除效果,选定华龙村4个典型水塘,以人工种植菱角(Trapa bispinosa)为试验对象,研究菱角对富营养化水体中总氮(TN)、硝态氮(NO_3~--N)、氨态氮(NH_4~+-N)、总磷(TP)及化学需氧量(CODCr)的净化能力。结果表明,经过75 d的试验研究,试验区水塘的TN、NH_4~+-N和NO_3~--N的浓度分别从55 mg/L、25 mg/L和3 mg/L降至13 mg/L、4.3 mg/L和2.1 mg/L,去除效率分别为62.3%、74.5%和23.5%;TP及CODCr的浓度从3.3 mg/L和120 mg/L分别降至1.45 mg/L和52.5 mg/L,去除效率为56.9%和56.3%;对照区水塘各营养元素去除率较低。菱角对农村废水中的N、P有一定的吸收作用,对重度富营养化水体,水生植物优先吸收NH_4~+-N,对TN的去除影响较大;NO_3~--N的去除主要依靠微生物的反硝化作用;TP的吸收需要更长的时间。菱角对重度富营养化农村废水营养盐的去除具有重要意义,且可以取得一定的经济效益。本研究为应用水生植物处理农村生活污水中的营养盐提供科学依据。  相似文献   

9.
为了解养殖模式对主养草鱼(Ctenopharyngodon idellus)池塘底泥微生物群落结构的影响,使用高通量测序方法分析了山塘、精养和鱼菜共生三种模式下草鱼池塘底泥微生物的结构特征。结果显示:(1)精养池塘水体CODMn、总氮(TN)和总磷(TP)[(35.67~108.34)mg/L、(3.40~7.93)mg/L、(1.35~2.19)mg/L]显著高于山塘[(2.67~24.33)mg/L、(0.77~3.30)mg/L、(0.38~0.77)mg/L]和鱼菜共生池塘[(31.67~58.50)mg/L、(2.40~3.43)mg/L、(0.81~1.22)mg/L],且养殖后期呈上升趋势,山塘和鱼菜共生池塘后期呈下降趋势。(2)三种模式条件下底泥微生物群落结构存在显著差异,但鱼菜共生与精养池塘底泥菌群结构相似性高于山塘模式;山塘池塘底泥微生物丰富度显著低于鱼菜共生和精养池塘,但多样性无显著性差异;山塘菌群多样性指数与环境因子无相关性,但精养模式ACE指数与TN、NH+4、TP、DO呈显著负相关,Shannon指数与TN和DO呈显著负相关;鱼菜共生模式ACE指数与NH+4、TP、CODMn呈显著正相关,Shannon指数与NH+4、TP、DO呈显著正相关。(3)山塘池塘核心菌群四季变化差异大;鱼菜共生和精养池塘核心菌群四季均以地杆菌属(Geobacter)、厌氧粘细菌属(Anaeromyxobacter)和脱氯单胞菌属(Dechloromonas)等厌氧和兼性厌氧菌为主。结果表明,鱼菜共生模式底泥微生物群落受环境因子影响小,能够达到控制水体CODMn和TN的目的。  相似文献   

10.
生态沟渠+稳定塘系统处理山区农村生活污水的研究   总被引：1，自引：0，他引：1  
研究流经生态沟渠+稳定塘系统的生活污水中悬浮物、氨氮、总氮、总磷、CODcr等指标的沿程变化以及去除效率,为探索山区农村生活污水治理模式提供依据和参考。生态沟渠由原农田排水渠经拓宽、种植植被改建而成,总长约150 m;稳定塘包括沉淀净化塘、生物净化塘和生物强化净化塘,分别栽种植物、栽种植物+吊养河蚌、栽种植物+放养鲢鳙,总面积约1 230 m2。在集水池出口、生态沟渠出口、稳定塘各塘出口各设1采样点共5个采样点。试验期间连续进水,进水平均流量约7 m3/h,系统总水力停留时间(HRT)约102 h,其中生态沟渠段约5.4 h、稳定塘段约96.6 h,首次采样在连续进水稳定运行1周后进行。在水力停留时间约为4 d的条件下,流经该系统的生活污水黑臭消失,浊度下降,出水DO饱和度达到65%以上,进水SS、NH3-N、TN、TP、CODcr的平均去除效率分别达到84.9%、70.1%、49.6%、44.9%和80.5%。生态沟渠段对SS具有较好的去除效果,达到40.1%,占系统总去除量的47%。系统最终出水可达到城镇污水处理厂污染物排放二级标准(GB18918-2002)。生态沟渠+稳定塘系统具有建造灵活、无需动力条件、运行成本低廉等特点,在小流域山区农村具有一定推广和应用前景。  相似文献   

11.
The total salt input in saline well water, mineral amendments, feed, and rainfall and runoff to ponds of an inland shrimp farm in Alabama was 1980.8 tonnes over a 5‐yr period. A residual of 270.4 tonnes of salt remained in pond water and 38.3 tonnes in bottom soil. Only 8.0 tonnes of salt were removed in harvested shrimp. A total of 1588.0 tonnes of salt or 80.2% of the input was lost to the environment with about equal amounts exiting the ponds in seepage and in overflow and harvest effluent. About 4.2% of the salt input (84.1 tonnes) could not be accounted for because of errors in assumptions and measurements. Salt concentration was elevated in a small stream passing through the farm and in the shallow aquifer beneath it. Needham Creek, the receiving water body for runoff and base flow from the farm watershed, had elevated salt concentrations when ponds were partially drained for harvest in the fall. At this time, chloride concentration exceeded 230 mg/L, the maximum concentration allowed by Alabama Department of Environmental Management regulations. Greater water reuse or more gradual release of pond effluent during harvest would reduce the peak in‐stream chloride concentration and avoid noncompliance with the in‐stream chloride criterion.  相似文献   

12.
人工湿地冬季净化减排水产养殖废水效果   总被引：2，自引：0，他引：2  
根据我国池塘养殖废水排放特点,研究了冬季人工湿地集中处理池塘养殖废水的效果。结果显示,在0.22 m/d水力负荷下,人工湿地对池塘养殖废水中总氮(TN)、总磷(TP)、化学需氧量(COD)和悬浮物(TSS)的去除率分别达到35.0%,38.2%,34.7%,91.6%;水力负荷上升至0.36 m/d后,人工湿地对TN和COD的去除率显著下降为20.0%和27.9%(P<0.05),TP和TSS去除率变化差异不显著(P>0.05),分别为35.7%和和93.2%。经人工湿地处理后出水TN浓度低于1.5 mg/L,TP浓度低于0.2 mg/L,COD浓度低于8 mg/L,TSS浓度低于5 mg/L,均满足水产养殖废水排放要求,表明应用人工湿地技术能有效实现池塘养殖废水的减排。另外,冬季低温使人工湿地对池塘养殖废水中TN和COD的去除率与夏季相比显著降低(P<0.05),但通过对人工湿地进行曝氧能够显著提高其对TN和COD的去除率(P<0.05)。  相似文献   

13.
洞庭湖氮磷时空分布及形态组成特征   总被引：2，自引：0，他引：2  
为探究洞庭湖水体营养盐形态结构与时空分布特征,分别于2014年8月(丰水期)和2015年1月(枯水期)在入湖河流、湖体、出湖口设置16个代表性断面采集水样,分析了氮、磷营养盐的特征指标。结果表明:1洞庭湖水体中,总氮(TN)含量为1.60~3.65 mg/L,平均值2.25 mg/L,总磷(TP)含量为0.060~0.359 mg/L,平均值0.138 mg/L;颗粒态总氮(TPN)含量为0.07~1.39 mg/L,平均值0.25 mg/L,颗粒态总磷(TPP)含量为0.003~0.172 mg/L,平均值0.05 mg/L;2时空分布上,水体中氮、磷含量整体表现为丰水期高于枯水期,出湖口最高,东洞庭湖高于西、南洞庭湖,入湖河流差异大的特征,颗粒态氮磷呈现自西向东呈逐渐增加趋势,与悬浮物(SS)的空间分布一致;3形态组成上,洞庭湖水体中氮磷以溶解态为主(TDN/TN为88.0%、TDP/TP为66.7%),三峡工程2003年蓄水前后,洞庭湖磷营养盐形态组成发生了大的变化,由以颗粒态磷为主(TDP/TP 20.0%~35.6%)转变为以溶解态为主,而氮营养盐形态组成基本未变;4营养结构上,洞庭湖大多数断面TN/TP在10~22,且氮、磷浓度远高于水体富营养的限制阈值,比较适宜藻类生长。相关分析显示,洞庭湖TN、TP、TDN、TDP均与Chl-a相关性不显著,因此认为洞庭湖氮、磷营养盐对藻类生长的限制作用不明显。  相似文献   

14.
Two separate geotextile bag systems were evaluated as a means for capturing and dewatering bio-solids in the effluent stream from recirculating aquaculture systems (RAS). Each geotextile bag system used a high molecular weight cationic polyacrylamide (PAM) polymer as a flocculant-aid. The two systems were operated under freshwater and brackish water conditions. A complete analysis including water quality and agronomic sludge analysis was conducted at the North Carolina State University Fish Barn – a large-scale, freshwater RAS demonstration and growout facility. An evaluation of water quality and performance of a similar geotextile bag system was also conducted at the Marine Aquaculture Research Center near Marshallberg, North Carolina, USA, under brackish conditions (15 PPT). Results indicated that performance of each of the systems was similar with TSS, COD, TN, and TP removal greater than 95%, 65%, 50%, and 38%, respectively, for both systems. Analysis of the sludge collected in the freshwater system after 70 days in a dewatering, inactive mode, showed a moisture content (MC) of 86%, or 14% dry matter (DM), indicating the system was effective at passively dewatering the bio-solids. Nutrient removal efficiency may be system specific based on the geotextile bag size and influent flow rate.Geotextile bag systems using flocculant-aids are an efficient means for capturing and dewatering waste solids from RAS effluents. Optimized geotextile bag system designs depend on flow rate, feed rate, and solids dewatering time, and fate of the treated effluent. This evaluation will aid in predicting the expected performance and determining the appropriate size of a geotextile bag system. The type of treatment required downstream from the geotextile bag system used for solids capture in a RAS wastewater treatment system will depend on the intended fate of the treated effluent.  相似文献   

15.
Sex reversal of early life stage tilapia (approximately 7–12 d post-hatch, total length averaging 9–11 mm, and total weight averaging 10–15 mg) is used commonly to produce populations of fish comprised of > 5% phenotypic females. The synthetic androgen, 17α-methyl testosterone (MT), is used to effect sex reversal in tilapia. This paper evaluates environmental impact and human food safety aspects of MT use for tilapia sex reversal based on a review of the scientific literature and on dilution models of farm discharge.
Effect of MT treatment on human food safety was evaluated by regression analysis of radioactivity depletion data and by dilution through growth analysis. Results show that the proposed use of MT for sex reversal of early life stage tilapia presents no negative effects on human food safety. Regression analysis of available depletion data from tilapia shows that whole-body concentrations of MT and metabolites in tilapia attain levels of <100 pg/g after 8 to 40 d of withdrawal, and that achievement of <10 pg/g of MT and metabolites in carcass tissue occurs after 6 to 50 d of withdrawal. These concentrations are attained well before completion of the FDA-required 120-d withdrawal period following MT treatment.
Standardized calculations were made to estimate MT concentration in effluents based on stocking rate and water exchange. Guidelines are provided for management of farms to ensure that effluent MT concentration remains < 1 μg/L. Given the expected concentration of MT in any farm effluents, the rapid dilution of effluent MT to very low levels in receiving waters, the sensitivity of MT to photo-oxidation, the expected rapid bacterial degradation of MT, and the limited total use of MT in the United States, we concluded that the use of MT-treated feed according to the proposed protocol will not cause significant adverse environmental effects.  相似文献   

16.
对虾养殖池沉积环境中TOC_TP_TN和pH垂直分布   总被引：11，自引：1，他引：10  
袁有宪 《水产学报》1999,23(4):363-367
１９９５年冬季,测定了青岛地区四个池龄１０年以上的对虾养殖池不同层次沉积物中有机碳（ＴＯＣ）、总氮（ＴＮ）、总磷（ＴＰ）和ｐＨ并研究了其垂直分布。结果表明,沉积物中的ＴＯＣ和ＴＮ污染较底层严重,泥质虾池表层污染较泥沙质更严重。沉积物中ＴＰ为输出过程而导致缺乏,ＴＰ的受扰动层与ＴＯＣ和ＴＮ的污染层基本一致。沉积物的ｐＨ无规律性变化。  相似文献   

17.
Effluents from three fish hatcheries were monitored for the discharge and subsequent downstream distribution of infectious pancreatic necrosis virus (IPNV). Samples of springwater and surface water, and tissues from salmonid and non-salmonid fish were assayed for IPNV. Water samples were processed to recover virus by adsorption to an electropositive, microporous filter matrix. No IPNV was detected in surface water collected above fish hatcheries or in hatchery springwater supplies. The virus could be detected for at least 19.3 km below the point of effluent discharge from hatcheries and the prevalence of IPNV infection in stream-resident fish was 2.8%.  相似文献   

18.
As environmental regulations become more stringent, environmentally sound waste management and disposal are becoming increasingly more important in all aquaculture operations. One of the primary water quality parameters of concern is the suspended solids concentration in the discharged effluent. For example, EPA initially considered the establishment of numerical limitations for only one single pollutant: total suspended solids (TSS). For recirculation systems, the proposed TSS limitations would have applied to solids polishing or secondary solids removal technology. The new rules and regulations from EPA (August 23, 2004) require only qualitative TSS limits, in the form of solids control best management practices (BMP), allowing individual regional and site specific conditions to be addressed by existing state or regional programs through NPDES permits. In recirculation systems, microscreen filters are commonly used to remove the suspended solids from the process water. Further concentration of suspended solids from the backwash water of the microscreen filter could significantly reduce quantity of discharge water. And in some cases, the backwash water from microscreen filters needs to be further concentrated to minimize storage volume during over wintering for land disposal or other final disposal options. In addition, this may be required to meet local, state, and regional discharge water quality. The objective of this research was an initial screening of several commercially available polymers routinely used as coagulation–flocculation aids in the drinking and wastewater treatment industry and determination of their effectiveness for the treatment of aquaculture wastewater. Based on the results of the initial screening, a further evaluation of six polymers was conducted to estimate the optimum polymer dosage for flocculation of aquaculture microscreen effluent and overall solids removal efficiency. Results of these evaluations show TSS removal was close to 99% via settling, with final TSS values ranging from as low as 10–17 mg/L. Although not intended to be used for reactive phosphorus (RP) removal, RP was reduced by 92–95% by removing most of the TSS in the wastewater to approximately 1 mg/L–P. Dosage requirements were fairly uniform, requiring between 15 and 20 mg/L of polymer. Using these dosages, estimated costs range from $4.38 to $13.08 per metric tonne of feed.  相似文献   

19.
鉴于上海市中心城区地表径流采用强排模式,由泵站排入受纳河道,常引起河道阶段性黑臭。为明确泵站放江污染对受纳河道的影响程度,选取中心城区典型泵站,在连续降雨期间监测评估了泵站放江水质、水量及其对受纳河道的影响程度。结果表明,在水量上,受连续降雨与泵站运行模式影响,降雨4.5 mm时的累积放江水量达61 410 m~3,放江水量达到服务区理论径流量的近7倍。在水质上,五日生化需氧量(BOD_5)、高锰酸盐指数(COD_(Mn))、氨氮(NH_3-N)和悬浮物(SS)事件平均浓度分别为43.2 mg/L、35.3 mg/L、33.4 mg/L和75.0 mg/L,细菌总数(total bacteria, TB)和大肠菌群(total coliforms, TC)事件平均浓度为6.8×10~6CFU/mL和5.7×10~5CFU/mL。对受纳河段而言,放江期间河段流速在3 cm/s左右,泵站放江污染物不能快速有效地扩散迁移,污水团在河道形成表观区域性黑臭,在排污口20 m范围内,主要污染物BOD_5、COD_(Mn)、NH_3-N和SS平均浓度与泵站放江水质接近,分别为35.0 mg/L、28.7 mg/L、28.1 mg/L和100.9 mg/L;TB和TC平均浓度为3.6×10~6CFU/mL和3.4×10~5CFU/mL。受河网流速影响,泵站排放口上下游样点受泵站放江影响小,相比而言,主要污染物变化趋势不显著。为有效降低排水系统雨天放江污染负荷,保障受纳河道水质改善效果,提出了挖掘截流设施潜力、推进雨污混接改造及加大河道生态修复力度等措施。  相似文献   

20.
《Aquacultural Engineering》2006,34(4):235-249
As environmental regulations become more stringent, environmentally sound waste management and disposal are becoming increasingly more important in all aquaculture operations. One of the primary water quality parameters of concern is the suspended solids concentration in the discharged effluent. For example, EPA initially considered the establishment of numerical limitations for only one single pollutant: total suspended solids (TSS). For recirculation systems, the proposed TSS limitations would have applied to solids polishing or secondary solids removal technology. The new rules and regulations from EPA (August 23, 2004) require only qualitative TSS limits, in the form of solids control best management practices (BMP), allowing individual regional and site specific conditions to be addressed by existing state or regional programs through NPDES permits. In recirculation systems, microscreen filters are commonly used to remove the suspended solids from the process water. Further concentration of suspended solids from the backwash water of the microscreen filter could significantly reduce quantity of discharge water. And in some cases, the backwash water from microscreen filters needs to be further concentrated to minimize storage volume during over wintering for land disposal or other final disposal options. In addition, this may be required to meet local, state, and regional discharge water quality. The objective of this research was an initial screening of several commercially available polymers routinely used as coagulation–flocculation aids in the drinking and wastewater treatment industry and determination of their effectiveness for the treatment of aquaculture wastewater. Based on the results of the initial screening, a further evaluation of six polymers was conducted to estimate the optimum polymer dosage for flocculation of aquaculture microscreen effluent and overall solids removal efficiency. Results of these evaluations show TSS removal was close to 99% via settling, with final TSS values ranging from as low as 10–17 mg/L. Although not intended to be used for reactive phosphorus (RP) removal, RP was reduced by 92–95% by removing most of the TSS in the wastewater to approximately 1 mg/L–P. Dosage requirements were fairly uniform, requiring between 15 and 20 mg/L of polymer. Using these dosages, estimated costs range from $4.38 to $13.08 per metric tonne of feed.  相似文献   

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