Recipient Water Bodies Research Articles

Design parameters for nitrogen removal by constructed wetlands treating mine waters and municipal wastewater under Nordic conditions

Nitrogen (N) loads from municipal and mine wastewater discharges typically increase N concentrations in recipient water bodies which should get more attention especially in cold-climate regions. This study compared N removal efficiency of six constructed wetlands (CWs) treating mine waters and three CWs polishing municipal wastewater. There were clear impacts of point source N loading to recipient water bodies in all cases studied and >300-fold increase in N was seen in some cases. First-order N removal coefficient was determined for seven of these CWs. All CWs studied were observed to remove N efficiently during the warm growing season but the amount of N released increased significantly during the cold season. Although some year-round purification was achieved by both peat-based and pond-type CWs, removal of nitrate + nitrite-N ((NO3− + NO2−)-N) was low during winter. The first-order N removal coefficient varied from 4.9 · 10−6 to 1.9 · 10−3 d−1 and showed that peat-based CWs were slightly more efficient in N removal than pond-type CWs. However, purification efficiency was steadier and higher for pond-type CWs, as lower hydraulic load or longer water residence time compensated for purification performance. Pond-type CWs showed mean removal efficiency of 59% and 46% for ammonium-N (NH4+-N) and (NO3− + NO2−)-N, respectively, whereas peatland-type CWs had lower removal efficiency for NH4+-N (mean of 26%) and in many cases negative removal for (NO3− + NO2−)-N. Correlation analysis revealed no clear, systematic relationship between temperature and N removal. However, in some CWs the highest correlation was between temperature and (NO3− + NO2−)-N, reflecting lower denitrification rate at lower temperature. More than 50% removal was found to require a hydraulic load below 10 mm d−1. In order to achieve 70% of NH4+-N removal, Ntot load lower than 75 g m−2 year−1 and a residence time longer than 80 d are needed in CWs in cold-climate regions.

Treatment of sanitary landfill leachate by the combination of photo-Fenton and biological processes

In this work, the pollutant reduction performance in landfill leachate by combining both photo-Fenton and biological processes was investigated. First, conventional biological treatment was performed, consisting of a decantation process, with centrifugation at 5000 rpm for 15 min, followed by the biological process conducted at 2.36 ± 0.1 mg mg−1 (BOD5/MLSS) and 0.571 ± 0.04 vvm (L L−1 min−1) for 40 h. At the same time, in the application of the photo-Fenton process, a central composite rotatable design (CCRD) was applied to evaluate the effect of main process variables. The quadratic models of chemical oxygen demand (COD) and 5 days biological oxygen demand (BOD5) removal were proposed and validated, being separately used as objective functions during the search for optimal operating conditions. After the application of the conventional biological process, removals of 87 ± 2% and 84 ± 2% were obtained for COD and BOD5, respectively. For the photo-Fenton process under optimum conditions (3400 mg H2O2 L−1, 80 mg Fe2+ L−1, pH = 2.40 and 120 min), removals of 89 ± 3% COD and 75 ± 1% BOD5 were obtained. However, both processes did not meet effluent discharge standards. So, the optimized photo-Fenton process was then combined with the biological process, performed for 150 h with 1.571 ± 0.06 vvm and 4.41 ± 0.3 mg mg−1 (BOD5/MLSS). With the combined process, it was possible to treat an effluent with high organic load, achieving a removal of 98% COD and BOD5 and meeting the restrictive standards of release in recipient water bodies.

Point source characterization of per- and polyfluoroalkyl substances (PFASs) and extractable organofluorine (EOF) in freshwater and aquatic invertebrates.

Major point sources of per- and polyfluoroalkyl substances (PFASs) cause ubiquitous spread of PFASs in the environment. In this study, surface water and aquatic invertebrates at three Swedish sites impacted by PFAS point sources were characterized, using homologue, isomer and extractable organofluorine (EOF) profiling as well as estimation of bioaccumulation factors (BAFs) and mass discharge. Two sites were impacted by fire training (sites A and R) and the third by industrial runoff (site K). Mean Σ25PFASs concentration in water was 1920 ng L-1 at site R (n = 3), which was more than 20- and 10-fold higher than those from sites A and K, respectively. PFOS was the most predominant PFAS in all waters samples, constituting 29-79% of Σ25PFAS concentrations. Several branched isomers were detected and they substantially contributed to concentrations in surface water (e.g. 49-78% of ΣPFOS) and aquatic invertebrates (e.g. 15-28% of ΣPFOS). BAFs in the aquatic invertebrates indicated higher bioaccumulation for long chain PFASs and lower bioaccumulation for branched PFOS isomers compared to linear PFOS. EOF mass balance showed that Σ25target PFASs in water could explain up to 55% of EOF at site R. However, larger proportions of EOF (>92%) remained unknown in water from sites A and K. Mass discharges were for the first time estimated for EOF and revealed that high amounts of EOF (e.g. 8.2 g F day-1 at site A) could be transported by water to recipient water bodies relative to Σ25PFASs (e.g. 0.15 g day-1 at site A). Overall, we showed that composition profiling, BAFs and EOF mass balance can improve the characterization of PFASs around point sources.

Efficiency of Flood Control Measures in a Sewer System Located in the Mediterranean Basin

Pollution induced by surface runoff in urban areas constitutes a significant problem. The adoption of control measures aimed at improving the quality of recipient water bodies is a fundamental issue in the management of Mediterranean Basin sewer systems. Previous research in Mediterranean areas using small virtual basins has shown that rainfall regimes have a limited impact on the pollutant load and discharge flowing into a receiving body. The aim of our research was to identify a sizing methodology for stormwater tanks located in the Mediterranean Basin. To achieve this, a numerical model of a sewer system, located in the Southern Iberian Peninsula, was developed. Different patterns related to peak periods of rainfall were considered. Furthermore, efficiency indices were used to evaluate and compare the effects of having a stormwater tank in the system. In our study (which considered a real area), significantly varied values were obtained for the pollution load removal rate (η) and the receiver overflow rate (θ). We nevertheless observed that, in our catchment, at a specific volume of V = 60 m3/ha, η and θ reached constant values without experiencing any significant improvement (η = 0.673 and θ = 0.133). Based on our model, this volume was proposed for the stormwater tank. The ATV (German Association for Water Pollution Control) A 128 standard was applied in order to validate the results, and the specific volume obtained (V = 60 m3/ha) matched with the one proposed. Thus, our proposed methodology is simple and different, and it is very easy to apply by obtaining the values of the efficiency indices η and θ through the development of a Storm Water Management Model (SWMM).

The Environmental Impact of Etelebou Flow Station In Surface Water of Gbarain, Bayelsa State, Nigeria

Environmental impact of anthropogenic activities from industrial sources, have become a threat to biodiversity. Water samples were collected from rivers around the flow station, and analysed from some physicochemical parameters and hydrocarbon contents. Result of the physicochemistry was reported for: pH (6.58± 0.04 - 6.76±0.01), conductivity (168.30±13.98 - 194.57±3.78 µS/cm), conductivity 8.29±0.04 - 10.66±0.02 NTU, salinity (0.07±0.00 - 0.09± 0.00 mg/l), and Total Solids (83.96±1.49 - 103.66±0.60mg/l). Other elemental analysis includes: sulphates (2.43±0.01 - 4.28 ±0.02 mg/l), nitrates (0.19±0.01 - 0.28±0.01 mg/l), carbonates (1.14±0.07 - 2.06±0.07 mg/l), calcium (8.45±0.10 - 11.70±0.25 mg/l), magnesium (1.14±0.07 - 2.56±0.03 mg/l), and sodium (4.37±0.15 - 5.62±0.03 mg/l). The values of THC and TPH were 0.92±0.08 - 1.51±0.03, and 0.37±0.13 - 0.76±0.07 mg/l respectively. Generally, the result indicated mild level of contamination in terms of Hydrocarbon contents. However, diagnostic data emerging for physicochemistry and some elemental property indicates the water is unfit for consumption. Notwithstanding, the order on contamination were reported as; downstream > midstream > upstream. Therefore this study concludes that there should be frequent monitoring of the recipient water bodies associated with the flow station in order to check anthropogenic activities, and conserve biodiversity.

Cellular stress response biomarkers for toxicity potential assessment of treated wastewater complex mixtures

AbstractBiomarker responses provide an early warning on environmental effects of water toxicants. The current work aimed to assess the stress biomarkers responses to toxicity potential of treated wastewater effluents in human intestinal epithelial Caco‐2 cells. Overall results of stress response genes overexpression confirmed the occurrence of water pollutants stressors which stimulate the modulation of biomarkers of effect mainly Heat shock proteins (Hsps), Metal‐responsive transcription factors, Calreticulin, Thioredoxin and P‐glycoprotein. Stress response genes were significantly overexpressed for all treated cells, revealing the activation of mechanisms of Caco‐2 cell protection mainly Hsp protection machinery and cellular defence against oxidative stress. Organic micropollutants associated with toxicity potential in treated effluents were identified. Stress response biomarkers assessment revealed human health and environmental impacts to take corrective measures to protect recipient water bodies from harmful effects of effluent discharges.

Toward measuring biogeochemistry within the stream‐groundwater interface at the network scale: An initial assessment of two spatial sampling strategies

AbstractIt is important to understand how point measurements across spatially heterogeneous ecosystems are scaled to represent these systems. Stream biogeochemistry presents an illustrative example because water quality concerns within stream networks and recipient water bodies motivate heterogeneous watershed studies. Measurements of the stream water‐groundwater (SW‐GW) interface (i.e., the shallow stream subsurface) are well‐documented for point‐scale sampling density measurements (i.e., cm2–m2 features), but poorly characterized for network‐scale sampling density measurements (i.e., km2; stream reaches and networks). Sampling the SW‐GW interface is more time and labor intensive than surface water sampling, meaning sample point selection must be made with care for network‐scale analyses. In this study, we endeavor to determine which of two common spatial sampling schemes is appropriate for characterizing SW‐GW interface biogeochemistry across a third‐order stream network, focusing on dissolved organic carbon. The first scheme, called Local Sampling, focuses on characterizing small‐scale (< 10 m2) variability produced by the local physical and biogeochemical heterogeneity, with fewer points across the stream network. The second scheme, called Longitudinal Sampling, has approximately the same number of measurements distributed over many more points across the stream network with less local variability characterization. This comparison reveals that selection of a Local Sampling versus a Longitudinal Sampling scheme influences the biogeochemical pattern interpretation at the stream network scale. Additionally, this study found that increasing observation efforts at the local scale added limited information for reach‐ to network‐scale biogeochemical patterns, suggesting that emphasis should be placed on characterizing variability across broader spatial scales with the Longitudinal Sampling approach.

Sawdust for Treatment of Stormwater - Test on Synthetic Stormwater Contaminated with Heavy Metals

Stormwater from urban, industrial and rural areas is very often discharged into recipient water bodies without any treatment. This is now changing in many parts of the word, especially in Europe due to The EU Water Framework Directive (European Union, 2000). According to the new policy, will probably stormwater that has often small concentrations but complex mix of different organic and inorganic pollutants has to be treated. Many different systems have been used, such as wetlands and soil infiltration trenches, among others. Sawdust has many times been reported as a good sorbent used for removing mostly toxic metals from wastewaters. However, in most cases, studies have been carried out with distilled water spiked with, for instance, 1-2 different toxic metals. Very few studies have used real wastewater and even less have studied removal of metals from stormwater using sorbent such as sawdust. Sawdust has also drawbacks, since it may release potentially hazardous substances as tannins: lignin, phenolic compounds, resin acids and overall high COD concentrations which results in oxygen depletion in the recipient water bodies. In this paper, the results of using sawdust as sorbent for removal of heavy metal from stormwater with different pollutants are presented.

Spatially differentiated midpoint indicator for marine eutrophication of waterborne emissions in Sweden

PurposeIn life cycle assessment (LCA), eutrophication is commonly assessed using site-generic characterisation factors, despite being a site-dependent environmental impact. The purpose of this study was to improve the environmental relevance of marine eutrophication impact assessment in LCA, particularly regarding the impact assessment of waterborne nutrient emissions from Swedish agriculture.MethodsCharacterisation factors were derived using site-dependent data on nutrient transport for all agricultural soils in Sweden, divided into 968 catchment areas, and considering the Baltic Sea, the receiving marine compartment, as both nitrogen- and phosphorus-limited. These new characterisation factors were then applied to waterborne nutrient emissions from typical grass ley and spring barley cultivation in all catchments.Results and discussionThe site-dependent marine eutrophication characterisation factors obtained for nutrient leaching from soils varied between 0.056 and 0.986 kg Neq/kg N and between 0 and 7.23 kg Neq/kg P among sites in Sweden. On applying the new characterisation factors to spring barley and grass ley cultivation at different sites in Sweden, the total marine eutrophication impact from waterborne nutrient emissions for these crops varied by up to two orders of magnitude between sites. This variation shows that site plays an important role in determining the actual impact of an emission, which means that site-dependent impact assessment could provide valuable information to life cycle assessments and increase the relevance of LCA as a tool for assessment of product-related eutrophication impacts.ConclusionsCharacterisation factors for marine eutrophication impact assessment at high spatial resolution, considering both the site-dependent fate of eutrophying compounds and specific nutrient limitations in the recipient waterbody, were developed for waterborne nutrient emissions from agriculture in Sweden. Application of the characterisation factors revealed variations in calculated impacts between sites in Sweden, highlighting the importance of spatial differentiation of characterisation modelling within the scale of the impact.

Wastewater Management Techniques: A Review of Advancement on the Appropriate Wastewater Treatment Principles for Sustainability

Water is an essential resource that is required to sustain life. Its availability has to be adequate, safe and easily accessible. Current trends in climate change and rise in human population has compromised water adequacy, availability and safety. Wastewater managers around the world have the responsibility to ensure that the effluent that is eventually released into the environment does not degrade the quality of the recipient water bodies. Attaining sustainability in wastewater management is top in the of Sustainable Development Goals’ Agenda. All in all, the realization of a more sustainable wastewater management will require a highly holistic and balanced approach in evaluating a particular management strategy's overall sustainability. Promoting the use of safe, affordable and adequately available wastewater treatment techniques is a step towards wastewater management for sustainability. This review paper therefore discusses some of the currently known and emerging wastewater management techniques that are considered essential in attaining sustainability in water resource management.

Adsorption of Orthophosphates in Water by Carbonaceus of Biological Origin as Adsorbent

The objective of this study was to evaluate the adsorption capacity calcareous skeleton of animal species (CSAS) in powder form compared to the commercial activated carbon (CAC) powder, as adsorbent for orthophosphates (P) removal from water. The experimental design selected was a factorial design with central composite rotational design (CCRD). In order to optimize the sorption process, a number of independent variables and levels were selected including: adsorption time; adsorbent/adsorbate ratio; pH and temperature. The orthophosphate (P) quantification was performed using the 4500-P E method. The P removal capacity with CAC powder varied from 0.15 to 4.86 mg/L. The maximum removal occurred at 1088 min, initial pH of 7.5, adsorbent/adsorbate ratio of 130, and temperature of 27 ºC. With the CSAS, the phosphorus removal varied from 0.70 to 6.11 mg/L. The maximum removal occurred at 735 min, with initial pH of 9.0, adsorbent/adsorbate ratio of 40 and temperature of 32 ºC. The conclusion is that the CSAS powder can become an interesting alternative as adsorbent material, both from economic and technical viewpoints in several applications, such as treatment of urban and industrial wastewaters and phosphorus removal/ retention to prevent eutrophication of recipient water bodies. Additionally, the final product (phosphorus-adsorbed CSAS powder) can be used as fertilizer and as soil pH adjustment.

The diversity of parasites in the Chinese sleeper Perccottus glenii Dybowski, 1877 (Actinopterygii: Perciformes) under the conditions of large-scale range expansion

It has been found that the species composition of parasites infesting the Chinese sleeper Perccottus glenii in water bodies from the nonnative part of its range is more depleted. Here, the phylogenetic distances between parasites exceed those in the native part of the range. It has been revealed that parasitological differences between P. glenii populations from the nonnative and native parts of the range, as well as between populations inside the nonnative part, have similar composition and abundance of the host-specific and euryxenous components in the parasitic fauna. It has been shown that these differences are determined by the genesis of sites from which P. glenii is introduced, as well as the local conditions of the recipient water bodies.

Probabilistic ecological risk assessment of effluent toxicity of a wastewater reclamation plant based on process modeling

The growing use of reclaimed wastewater for environmental purposes such as stream flow augmentation requires comprehensive ecological risk assessment and management. This study applied a system analysis approach, regarding a wastewater reclamation plant (WRP) and its recipient water body as a whole system, and assessed the ecological risk of the recipient water body caused by the WRP effluent. Instead of specific contaminants, two toxicity indicators, i.e. genotoxicity and estrogenicity, were selected to directly measure the biological effects of all bio-available contaminants in the reclaimed wastewater, as well as characterize the ecological risk of the recipient water. A series of physically based models were developed to simulate the toxicity indicators in a WRP through a typical reclamation process, including ultrafiltration, ozonation, and chlorination. After being validated against the field monitoring data from a full-scale WRP in Beijing, the models were applied to simulate the probability distribution of effluent toxicity of the WRP through Latin Hypercube Sampling to account for the variability of influent toxicity and operation conditions. The simulated effluent toxicity was then used to derive the predicted environmental concentration (PEC) in the recipient stream, considering the variations of the toxicity and flow of the upstream inflow as well. The ratio of the PEC of each toxicity indicator to its corresponding predicted no-effect concentration was finally used for the probabilistic ecological risk assessment. Regional sensitivity analysis was also performed with the developed models to identify the critical control variables and strategies for ecological risk management.

Chlorination-induced genotoxicity in the mussel Perna viridis: assessment by single cell gel electrophoresis (comet) assay

Mussels are important fouling organisms in the cooling water systems of coastal power plants. Continuous low-dose chlorination (CLDC) is being practiced as an effective method to control mussel biofouling in power plant cooling water systems. CLDC effectively controls mussel fouling by discouraging larval settlement rather than by killing the larvae or adults. Mussels are an integral part of the natural benthic community in the receiving water body where the coolant water is discharged. Hence, from a toxicological point of view, they can serve as both target and non-target organisms. Previous researchers have indicated that chlorine residual, rather than elevated temperature, can be the major stress factor in the effluents released from coastal power plants. However, very little data are available on the sub-lethal effects of low level chlorination on representative benthic fauna. In this study, we used native and transplanted mussels (Perna viridis) to study lethal and sub-lethal effects of chlorination in the cooling water circuit of an operating power plant. Experiments involving comet assay suggested that CLDC can cause DNA damage in treated mussels. However, activation of DNA repair appeared to get initiated after the accrued damage reached a threshold. The results indicate that, at chlorine residual levels observed at the discharge point, exposure to chlorinated effluents is unlikely to cause significant genetic damage to mussels in the recipient water body.

The specific rate of the population dynamics of the black-striped pipefish Sygnathus nigrolineatus Eichwald, 1831 in the Kremenchug and Dneprodzerzhinsk reservoirs at different phases of the naturalization of the species

The possible causes of the invasion of the black-striped pipefish Sygnathus nigrolineatus Eichwald, 1831 into two water reservoirs of the Dnieper Cascade of Hydroelectric Stations are described. The average, maximum, and minimum specific rates of the change of the abundance of the species in the recipient water bodies are analyzed since the onset of the invasion. Specification of different phases of naturalization is based on the analysis of dynamic phase portraits of the species abundance. The periods of the equilibrium states of the population are revealed. The potential rates of the increase of the species abundance in the Dneprodzerzhinsk and Kremenchug reservoirs are assessed.

A Pre-screening Procedure for Pollution Source Identification in Sewer Systems

Abstract Illicit intrusions in Sewer Systems (SSs), modifying the wastewater characteristics, may create problems to the treatment plant and/or to the final recipient water body. For this reason, the source identification (SI) problem is becoming an important issue also in SSs. For large real systems, the computational burden might make the SI methodologies impractical. In this paper a pre-screening procedure, based on the pollution matrix concept, is introduced and applied before the SI methodology. Selecting a group of possible candidate nodes and cutting consequently the scheme, a significant improvement both in terms of time and the accuracy is obtained.

Lifting China's water spell.

China is a country with significant but unevenly distributed water resources. The water stressed North stays in contrast to the water abundant and polluted South defining China's current water environment. In this paper we use the latest available data sets and adopt structural decomposition analysis for the years 1992 to 2007 to investigate the driving forces behind the emerging water crisis in China. We employ four water indicators in China, that is, freshwater consumption, discharge of COD (chemical oxygen demand) in effluent water, cumulative COD and dilution water requirements for cumulative pollution, to investigate the driving forces behind the emerging crisis. The paper finds water intensity improvements can effectively offset annual freshwater consumption and COD discharge driven by per capita GDP growth, but that it had failed to eliminate cumulative pollution in water bodies. Between 1992 and 2007, 225 million tones of COD accumulated in Chinese water bodies, which would require 3.2-8.5 trillion m(3) freshwater, depending on the water quality of the recipient water bodies to dilute pollution to a minimum reusable standard. Cumulative water pollution is a key driver to pollution induced water scarcity across China. In addition, urban household consumption, export of goods and services, and infrastructure investment are the main factors contributing to accumulated water pollution since 2000.

DOC and CO2-C Releases from Pristine and Drained Peat Soils in Response to Water Table Fluctuations: A Mesocosm Experiment

Hydrological conditions are considered to be among the main drivers influencing the export of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems, and hydrology is likely to alter due to climate change. We built a mesocosm experiment by using peat profiles from a pristine and from a drained (drained in 1978) peatland. A several-week-long low water table period followed by a high water table period, that is, a setting mimicking drought followed by flood, released relatively more DOC from pristine peat than from drained peat. From pristine peat profiles DOC was released into soil water in such quantities that the concentration of DOC remained stable despite dilution caused by added spring water to the mesocosms. In drained peat the DOC concentrations decreased during the high water table period indicating stronger dilution effect in comparison to pristine peat. At the landscape level DOC load from a drained peatland to the recipient water body may, however, increase during flooding because of high water runoff out of the peatland containing high DOC concentrations relative to the forest and agricultural areas. During the high water table period neither peat type nor water table had any clear impact on carbon dioxide (CO2-C) fluxes.

Water retention in ponds and the improvement of its quality during carp production / Retencjonowanie wody w stawach oraz poprawa jej jakości w procesie produkcji karpiowej

Abstract Ponds play various functions both productive and non-productive. It was demonstrated in the paper that ponds retain water and during heavy rainfalls they act as a flood control measure. Self-purification of water takes place along the pond. Statistically significant reduction of nitrate-N, phosphate-P and calcium concentrations was found in pond water. From 102±24 to as much as 360±53 kg nitrate-N per ha of fishpond is retained during fish growth. Phosphorus may not be retained in fishpond; if it is then the amounts of stored P are small (from 1 to 7 kg·ha-1 on average). Slightly more potassium may remain in the pond. After the period of fish growth and draining the pond, only part of stored load of nutrients reaches the recipient water body. From 200 to 400 kg N-NO3 and up to 2300 kg Ca per ha does not flow out of the pond. The outflow of ammonium-N, phosphorus and potassium may, however, increase or decrease

Impact Assessment on the Aquatic Ecosystem in the Vicinity of an Operating Nuclear Power Plant at the Kalpakkam Coastal Site

An inherent problem in electricity generation is that much of the heat produced cannot be converted into electricity and is dissipated in nearby heat sinks, such as lakes, rivers and oceans. In India, such heat rejection to water bodies is governed by legislation from ministry of environment and forests and central and state pollution control boards. New standards for thermal discharge issued by MoE&F in 1998 seem to be very stringent. But in the absence of relevant data for Indian sites appear to be somewhat justified. In order to make a realistic assessment of the impact of thermal discharge on aquatic ecosystems, the Department of Atomic Energy initiated the first major thermal ecological study in the country at two of its operating nuclear power plants, one at a coastal site in Kalpakkam and the other on the banks of river Kali at Kaiga. The 5 years duration co-ordinated research project involved researchers from eight different universities and national laboratories and experts from NIO, NIOT, CECRI, BARC, NPCIL and MoE&F. In view of the fact that the most of the forthcoming nuclear power plants in the country are coastally located, this article discusses the findings of Thermal Ecological Study at Kalpakkam. A major achievement of the study was to map the precise boundaries of the small mixing zone, the region of confluence of the heated water with the recipient water body, wherein the thermal plume effected a ∆T of only 3–5 °C due to rapid inundation and mixing with turbulent sea water. This caused a limited impact on the growth and distribution of the relatively sedentary benthic flora and fauna, though none of the motile forms, including fishes, were affected. Beyond the mixing zone, the life appeared to be as near normal as possible. No change in any physico-chemical parameter was noticed, except for a small expected decrease in dissolved oxygen at the discharge point. At Kalpakkam, position of the mixing zone shifts periodically due to formation of a natural sand bar by sea currents. This allows restoration of parameters, especially temperature to more conducive values and results in recolonization of the previously impacted sites. An ecologically encouraging finding of the study was that the impact was restricted in space and reversible in time. The data generated are expected to aid regulatory agencies in formulation of more appropriate stipulations for thermal discharge and also guide power industry to design eco-friendly technologies in future.