Water Discharge Points Research Articles

Alternative approach for assessment and limitation of environmental impacts from desalination plant water discharges by substitution of the „mixing zone” by a „minimum dilution volume”

Desalination plants are processing huge quantities of sea water for the production of high quality potable and process water. With regard to environmental impact the main concerns are the increased temperature and salinity of the process effluent (brine, cooling water) which has to be rejected to the sea. Many national and international environmental regulations and guidelines are stipulating discharge limits for temperature and salinity to be complied with by the projected desalination plant in order to obtain the environmental approval for operation. The World Bank guidelines, as well as many national regulations, assume a so called „Mixing Zone” around the point of water discharge, within which initial mixing with ambient sea water takes place, and stipulate limits for temperature and salinity increase over ambient conditions at the edge of this mixing zone. However, the size of this mixing zone is not clearly defined and the procedures by which the temperature and salinity values are to be determined are missing. In consequence compliance with the stipulated discharge limits can hardly be proven in quantitative terms and the results of Environmental Impact Assessment (EIA) reports are usually rather imprecise in this regard. This presentation describes in a simplified manner an alternative approach for assessment of the environmental impact and corresponding limitation of temperature and salinity increase due to water discharge from desalination and power plants, which is considered more adequate for this purpose. It is proposed to substitute the unclear criterion of a „Mixing Zone” size by the water volume available for dilution of the discharged effluent. A basic procedure for the determination of a minimum dilution water volume is outlined, considering the temperature or salinity increase between intake and outfall and the discharged water flow rate. The described general approach may be considered by both environmental authorities stipulating discharge limits and the responsible project parties to enable a more adequate assessment regarding compliance of a desalination project with applicable environmental regulations on a sound data basis.

Effect of lixiviated sediments affected with treated water on Selenastrum capricornutum, Printz and Origanum vulgare L.

Xochimilco is an area of Mexico City fulfilling important ecological functions. However, the water of the canal network in the lacustrine zone of Xochimilco is supplied by the water treatment plants of the city, implying a risk of accumulated contaminants in the sediments. This study reports the effect of lixiviates obtained from sediments collected in the canals of Xochimilco on the growth of the alga Selenastrum capricornutum and the angiosperm Origanum vulgare. Three factors were tested: (a) water source in terms of the effluent from the two water treatment plants (urban waste-water, located at Cerro de la Estrella (CE) and urban-rural waters at San Luis Tlaxialtemalco (SLT); (b) sampling season (January, dry season; May and September, rainy season; and (c) distances from the water discharge point in the Xochimilco's main canal (5200 and 1000 m for CE, and 0, 200 m for SLT). The chemical water properties analyzed were: pH, electrical conductivity, N-NO3, N-NH3, NTotal, P-PO4 and PTotal. The alga was more sensitive to the contaminants than O. vulgare, showing growth inhibition of 93–100%. The effect of sampling season on the inhibition of algal growth was ordered as follows: September > May > January. Lixiviates obtained from sediment samples 200 and 1000 m from the main point of water discharge caused a higher algal growth inhibition than the samples obtained at the source point. Lixiviate promoted the growth of seedlings of O. vulgare.

English

Artesian discharges of net alkaline, ferruginous waters from abandoned underground lead-zinc mines cause considerable surface water degradation at the Tar Creek Superfund Site, part of the historic Tri-State Mining District of Oklahoma, Kansas and Missouri. Two perennial borehole discharges, identified as the lowest elevation mine water discharge points in the district, have flowed unabated for almost 30 years and considerably degraded the physical, chemical and biological integrity of a first-order tributary to Tar Creek. Based on a comprehensive water quality and quantity characterization study, a large multi-cell passive treatment system was designed to receive approximately 1000 L/minute of mine water flowing from these abandoned boreholes (pH 5.95±0.06, total alkalinity 393±18 mg/L CaCO3, total acidity 364±19 mg/L CaCO3, Fe 192±10 mg/L, Zn 11±0.7 mg/L, Cd 17±4 ug/L, Pb 60±13 ug/L and As 64±6 ug/L). The objectives of this project include: i) remediation of polluted mine waters to acceptable quality for maintenance of the receiving water body aquatic community, ii) demonstration of the first mine water treatment facility of any kind in the Tri-State Mining District, and iii) technology transfer to speed application of this technology to other locations. The passive treatment system includes an initial oxidation pond followed by parallel treatment trains (to facilitate research and experimentation) consisting of aerobic wetlands, vertical-flow bioreactors, re-aeration ponds (with active aeration via wind and solar power) and horizontal-flow limestone beds. Waters from the parallel trains are recombined in a polishing wetland prior to final discharge. Total design surface water elevation change in the entire system is approximately 1.8 m. Prior to system implementation, the abandoned boreholes required rotosonic over-drilling to establish hydraulic control. In addition, diversion of storm water flows from an approximately 470-ha upgradient watershed was necessary. During construction, a third mine water discharge was discovered and incorporated into the design. This system represents a state of the art ecological engineering research site for passive treatment of mine waters.

Evaluation of pollutants removal efficiency to achieve successful urban river restoration

Greater efforts to provide alternative scenarios are key to successful urban stream restoration planning. In this study, we discuss two different aspects of water quality management schemes, biodegradation and human health, which are incorporated in the restoration project of original, pristine condition of urban stream at the Gwangju (GJ) Stream, Korea. For this study, monthly monitoring of biochemical oxygen demand (BOD(5)) and fecal indicator bacteria (FIB) data were obtained from 2003 to 2008 and for 2008, respectively, and these were evaluated to explore pollutant magnitude and variation with respect to space and time window. Ideal scenarios to reduce target pollutants were determined based on their seasonal characteristics and correlations between the concentrations at a water intake and discharge point, where we suggested an increase of environmental flow and wetland as pollutants reduction drawing for BOD(5) and FIB, respectively. The scenarios were separately examined by the Qual2E model and hypothetically (but planned) constructed wetland, respectively. The results revealed that while controlling of the water quality at the intake point guaranteed the lower pollution level of BOD(5) in the GJ Stream, a wetland constructed at the discharge point may be a promising strategy to mitigate mass loads of FIB. Overall, this study suggests that a combination of the two can be plausible scenarios not only to support sustainable urban water resources management, but to enhance a quality of urban stream restoration assignment.

삼보광산 하류 수계의 계절별 수질변화와 오염도 평가

폐금속 광산에서 유출되는 광산배수로 인한 수계의 수질오염 영향을 파악하기 위하여 삼보광산 광미댐 침출수 및 하류 하천수의 화학성분 및 미량금속을 분석 검토한 결과는 다음과 같다. 삼보광산 주변 광미댐 침출수의 pH 값은 <TEX>$5.8{\sim}6.9$</TEX> 사이로 중성에 가까운 약산성이였다. 주 광미댐 침출수의 주요 용존 화학성분 평균치는 EC 1.77 dS/m, <TEX>$SO_4^{2-}$</TEX> 929, <TEX>$K^+$</TEX> 14.6, <TEX>$Ca^{2+}$</TEX> 263.3, <TEX>$Mg^{2+}$</TEX> 46.9 mg/L 이였다. 특히 화학성분 중 EC 값과 <TEX>$SO_4^{2-}$</TEX> 농도는 벼의 농업용수 피해한계 농도 (EC 1.0 dS/m, <TEX>$SO_4^{2-}$</TEX> 54.0 mg/L)를 상회하였다. 광산 침출수의 Cd 평균 농도(<TEX>$0.016{\sim}0.021\;mg/L$</TEX>)는 농업용수 수질기준인 0.01 mg/L을 초과하였고, Cd 최고치는 수질기준의 4배정도 높았다. 또한 미량금속 중 Zn, Fe 및 Mn 농도는 FAO의 관개용수 최대 권고치(Cd 0.01, Zn 2.0, Fe 5.0, Mn 0.2 mg/L)를 초과하였고, 특히 Zn 및 Mn 평균 농도는 권고치의 <TEX>$8{\sim}26$</TEX>배, <TEX>$45{\sim}313$</TEX>배 이상 높았다. 본 조사결과에서 광산배수에 의한 수계의 수질오염은 하류 1 km 이상까지 영향을 미치는 것으로 나타났다. 광산배수와 하천수의 수질항목 중 pH 값은 용존 Cd, Zn, Al 및 Mn 농도와 부의 상관을, 주 오염성분인 EC 값, <TEX>$SO_4^{2-}$</TEX> 및 <TEX>$Ca^{2+}$</TEX> 농도는 각각의 Cd, Zn, Al 및 Mn 농도와 고도의 정의 상관을 보였다. 또한 주요 화학성분 중에서는 pH 값이 EC 값 및 <TEX>$SO_4^{2-}$</TEX> 농도와 부의 상관을 보였다. Metal mining district drainage is a well recognized source of environmental contamination. Oxidation of metal sulfides produces acidic and metal-rich waters that contaminate local surface water and ground water in mines, mine dumps, and tailing impoundments. This monitoring study was carried out to investigate the stream water quality and pollution as affected by the Sambo mine drainage in relation to the relative distance from the mine. It obvious that pH values of the mine drainage ranged from 5.8 to 6.9, while the average concentrations of the dissolved chemical constituents for EC, <TEX>$SO_4^{2-}$</TEX>, <TEX>$K^+$</TEX>, <TEX>$Ca^{2+}$</TEX>, and <TEX>$Mg^{2+}$</TEX> were <TEX>$1.77\;dS\;m^{-1}$</TEX>, 929, 14.6, 263.3, and 46.9 mg/L in mine drainage discharged from the main waste rock dumps (WRD), respectively. Furthermore, EC values and sulfate concentrations exceeded the critical toxicity levels in agricultural water for rice plant (<TEX>$1.0\;dS\;m^{-1}$</TEX> for EC and 54.0 mg/L for <TEX>$SO_4^{2-}$</TEX>). Also, the average of dissolved cadmium concentrations (<TEX>$0.016{\sim}0.021\;mg/L$</TEX>) was higher than water quality standard (0.01 mg/L) for agricultural water in Korea, in addition to Zn, Fe and Mn were higher than trace metals maximum concentrations which recommended by FAO for irrigation water. The results indicate that mine drainage discharged from the Sambo mine affected stream water at least to distance of 1 km downstream of the mine water discharge point. EC values, <TEX>$SO_4^{2-}$</TEX> and <TEX>$Ca^{2+}$</TEX> concentrations in discharged water positively correlated with dissolved Cd, Zn, Al and Mn concentrations, while the pH values negatively correlated. In addition, EC values, <TEX>$SO_4^{2-}$</TEX> and <TEX>$Ca^{2+}$</TEX> concentrations were negatively correlated with pH values.

Invasive species and coal bed methane development in the Powder River Basin, Wyoming

One of the fastest growing areas of natural gas production is coal bed methane (CBM) due to the large monetary returns and increased demand for energy from consumers. The Powder River Basin, Wyoming is one of the most rapidly expanding areas of CBM development with projections of the establishment of up to 50,000 wells. CBM disturbances may make the native ecosystem more susceptible to invasion by non-native species, but there are few studies that have been conducted on the environmental impacts of this type of resource extraction. To evaluate the potential effects of CBM development on native plant species distribution and patterns of non-native plant invasion, 36 modified Forest Inventory and Analysis plots (each comprised of four 168-m2 subplots) were established in the Powder River Basin, Wyoming. There were 73 168-m2 subplots on control sites; 42 subplots on secondary disturbances; 14 on major surface disturbances; eight on well pads; and seven on sites downslope of CBM wells water discharge points. Native plant species cover ranged from 39.5 +/- 2.7% (mean +/- 1 SE) in the secondary disturbance subplots to 17.7 +/- 7.5% in the pad subplots. Non-native plant species cover ranged from 31.0 +/- 8.4% in the discharge areas to 14.7 +/- 8.9% in the pad subplots. The control subplots had significantly less non-native species richness than the combined disturbance types. The combined disturbance subplots had significantly greater soil salinity than the control sites. These results suggest that CBM development and associated disturbances may facilitate the establishment of non-native plants. Future research and management decisions should consider the accumulative landscape-scale effects of CBM development on preserving native plant diversity.

Water chemistry and ecotoxicity of an acid mine drainage-affected stream in subtropical China during a major flood event

Field and laboratory work was carried out to investigate the chemistry and ecotoxicity of stream water affected by acid mine drainage in a tributary catchment of the Pearl River in subtropical China during a major flood that corresponded to a return period of 100 years. The results indicate that stream water was affected by acid mine drainage from the Dabaoshan mine at least to a distance of 25 km downstream of the mine water discharge point. It appears that H + generated from sulfide oxidation in the waste rock dumps was readily available for exporting. The amount of H + being discharged into the receiving stream depended on the volume of out-flowing waters. However, there was a lag time for the discharges of the metals. This may be attributed to the slower release of metals, relative to H +, because it might take more time for the dissolution of heavy metal-bearing compounds, particularly the sparsely soluble jarosites. Fe, Zn and Al were the major metals of potential toxicity contained in the AMD-affected stream water, followed by Mn, Cu, Pb, As, Cd and Ni. The concentrations of these metals in the water decreased rapidly down the stream. This corresponds with an increase in the concentrations of reactive heavy metal fractions in benthic mud down the stream, reflecting the precipitation of heavy metal compounds with increasing pH and their subsequent deposition in the streambed. Toxicity tests show that the AMD-affected stream water at 3.5 km downstream of the discharge point was highly toxic to the test organism. At 25 km downstream of the discharge point where stream water pH was as high as 5.75, marked toxic responses of the test organism were still observed.

Revisiting a Classification Scheme for U.S.‐Mexico Alluvial Basin‐Fill Aquifers

Intermontane basins in the Trans-Pecos region of westernmost Texas and northern Chihuahua, Mexico, are target areas for disposal of interstate municipal sludge and have been identified as possible disposal sites for low-level radioactive waste. Understanding ground water movement within and between these basins is needed to assess potential contaminant fate and movement. Four associated basin aquifers are evaluated and classified; the Red Light Draw Aquifer, the Northwest Eagle Flat Aquifer, the Southeast Eagle Flat Aquifer, and the El Cuervo Aquifer. Encompassed on all but one side by mountains and local divides, the Red Light Draw Aquifer has the Rio Grande as an outlet for both surface drainage and ground water discharge. The river juxtaposed against its southern edge, the basin is classified as a topographically open, through-flowing basin. The Northwest Eagle Flat Aquifer is classified as a topographically closed and drained basin because surface drainage is to the interior of the basin and ground water discharge occurs by interbasin ground water flow. Mountains and ground water divides encompass this basin aquifer on all sides; yet, depth to ground water in the interior of the basin is commonly >500 feet. Negligible ground water discharge within the basin indicates that ground water discharges from the basin by vertical flow and underflow to a surrounding basin or basins. The most likely mode of discharge is by vertical, cross-formational flow to underlying Permian rocks that are more porous and permeable and subsequent flow along regional flowpaths beneath local ground water divides. The Southeast Eagle Flat Aquifer is classified as a topographically open and drained basin because surface drainage and ground water discharge are to the adjacent Wildhorse Flat area. Opposite the Eagle Flat and Red Light Draw aquifers is the El Cuervo Aquifer of northern Chihuahua, Mexico. The El Cuervo Aquifer has interior drainage to Laguna El Cuervo, which is a phreatic playa that also serves as a focal point of ground water discharge. Our evidence suggests that El Cuervo Aquifer may lose a smaller portion of its discharge by interbasin ground water flow to Indian Hot Springs, near the Rio Grande. Thus, El Cuervo Aquifer is a topographically closed basin that is either partially drained if a component of its ground water discharge reaches Indian Hot Springs or undrained if all its natural ground water discharge is to Laguna El Cuervo.

Willingness to pay to improve domestic water supply in rural areas of Central Tanzania: Implications for policy

SUMMARY This analysis estimates willingness to pay to improve community-based rural water utilities in the Dodoma and Singida Regions of Central Tanzania, using Multinomial Logit functions. An estimate of willingness to pay provides an indication of the demand for improved services and potential for them being sustainable. Surveys were conducted in a total of 30 villages in the two regions. In the Dodoma Region, about 14% of respondents indicated that they were satisfied with the status quo, 64% suggested increasing water discharge and watering points, and 22% proposed other improvements relating to water quality. In the Singida Region, 31% of the respondents were satisfied with the status quo, 59% wanted deeper boreholes and watering points, and 10% indicated other types of improvement relating to water quality. The Multinomial Logit functions indicated that the interaction between the water quality variable and proposed bids were important in making choices with reference to the type of improvement desired. Respondents who wanted to increase water supply in Dodoma Region were willing to pay 32 Tsh above the existing tariff of 20 Tsh/bucket. In the Singida Region, the analogous amount was 91 Tsh per household per year above the existing user fee of 508 Tsh per household per year. If the tariff or user fees have to be increased, the estimated average potential revenue for the surveyed villages was 252 million Tsh/year (US$265 263) in the Dodoma Region, and 5.2 million Tsh/year (US$5474) in the Singida Region. In the future, strategic planning is needed to ensure that improvements proposed potentially improve cost recovery initiatives and increase the level of consumer satisfaction. Also, care will be needed to ensure that more disadvantaged community members do not suffer unduly from increases in tariff or user fees.

Influence of anthropogenic activity on the vertical distribution of Zn, Cd, Pb and Cu in interstitial water and coastal marine sediments (Cádiz bay, SW Spain)

The vertical profiles of Zn, Cd, Pb and Cu were determined for sediment and interstitial water from three stations in Cádiz Bay. The concentrations of the different metals measured in the surface sediments depend on the distance from the waste water discharge points existing in this zone and on their nature (urban or industrial). The highest levels of Pb and Cd (70 and 0.31 µg g–1, respectively) were found near urban effluents, and the highest levels of Zn and Cu (230 and 106 µg g–1, respectively) near industries related to the construction of ships. The vertical profiles of Zn, Cd, Pb and Cu in both sediment and interstitial water show an important increase in concentrations in the surface layers and are relatively constant from 20 cm. The interstitial water concentrations are lower than the sediment concentrations, ranging from 13 to 57 µg L–1 for Zn, from 3 to 11 µg L–1 for Pb, from 9 to 320 µg L–1 for Cu and from 0.07 to 2.4 µg L–1 for Cd. The values obtained for the geoaccumulation index reported by Müller (1979) classify the study area as intermediate, between an uncontaminated and moderately contaminated ecosystem. The surface enrichment factor values calculated for the four metals from the different stations suggest a unique origin of metal contamination in this zone.

Primary production of microphytobenthos in the Ems-Dollard Estuary

From 1976 through 1978 primary production of microphytobenthos was measured at 6 stations on intertidal flats in the Ems-Dollard estuary using the 14C method. The purpose of the measurements was to estimate the annual primary production at different sites in the estuary and to investigate the factors that influence the rates of primary production. Therefore benthic chlorophyll a and a set of environmental factors were measured. Only primary production correlated sigruficantly with chlorophyll a concentration in the superficial (0.5 cm) sediment layer; other factors (temperature. in situ irradiance) did not correlate with primary production, primary production rate or assimilation number. Annual primary production ranged from ca. 50 g C m-' to 250 g C m-2 and was closely related to elevation of the tidal flat station. However, highest values were also recorded at the station closest to a waste water discharge point in the inner part of the estuary. Annual primary production can be roughly estimated from the mean annual content of chlorophyll a in the sediment. Use of different calculation methods results in annual primary production values that do not differ greatly from each other. Also productivity rates did not differ much over most of the estuary, except at the innermost station which showed a high production rate in combination with high microalgal biomass; this could not be explained by the high elevation of the station alone. A hypothesis is offered to explain the limited primary production of microphytobenthic vegetations.