Water quality and pollution loading of a river segment affected by landfill leachate and domestic waste

The Marikina River in the Philippines has been polluted by Payatas landfill leachate, and domestic and agricultural waste. This study monitored the water quality at five stations on the river and two stations on two creeks that discharge to the river to determine the effects of Payatas landfill and to estimate pollution loading. The dissolved oxygen (DO), chemical oxygen demand (COD) and other water quality parameters were compared with the Philippines Standards for river water classification. It was found that Payatas leachate has a significant influence on the DO and COD levels as well as other water quality parameters. Per capita pollution loading for Quezon City was found to be lower than for Europe and Japan. The effect of leachate is more significant during the dry season. It is recommended that a leachate collection system be established to prevent leachate form entering Payatas creek, and that the Patayas landfill be replaced with a modern landfill site, conforming to current best practice at another location.

List of Abbreviation: BOD= Biological Oxygen Demand COD = Chemical Oxygen Demand DO = Dissolved Oxygen EC = Electrical Conductivity M1, M2, M3, M4, M5 = monitoring stations TDS = Total Dissolved Solids TSS = Total Suspended Solids     

A new risk assessment approach for the prioritization of 500 classical and emerging organic microcontaminants as potential river basin specific pollutants under the European Water Framework Directive

Given the huge number of chemicals released into the environment and existing time and budget constraints, there is a need to prioritize chemicals for risk assessment and monitoring in the context of the European Union Water Framework Directive (EU WFD). This study is the first to assess the risk of 500 organic substances based on observations in the four European river basins of the Elbe, Scheldt, Danube and Llobregat. A decision tree is introduced that first classifies chemicals into six categories depending on the information available, which allows water managers to focus on the next steps (e.g. derivation of Environmental Quality Standards (EQS), improvement of analytical methods, etc.). The priority within each category is then evaluated based on two indicators, the Frequency of Exceedance and the Extent of Exceedance of Predicted No-Effect Concentrations (PNECs). These two indictors are based on maximum environmental concentrations (MEC), rather than the commonly used statistically based averages (Predicted Effect Concentration, PEC), and compared to the lowest acute-based (PNEC_acute) or chronic-based thresholds (PNEC_chronic). For 56% of the compounds, PNECs were available from existing risk assessments, and the majority of these PNECs were derived from chronic toxicity data or simulated ecosystem studies (mesocosm) with rather low assessment factors. The limitations of this concept for risk assessment purposes are discussed. For the remainder, provisional PNECs (P-PNECs) were established from read-across models for acute toxicity to the standard test organisms Daphnia magna, Pimephales promelas and Selenastrum capricornutum. On the one hand, the prioritization revealed that about three-quarter of the 44 substances with MEC/PNEC ratios above ten were pesticides. On the other hand, based on the monitoring data used in this study, no risk with regard to the water phase could be found for eight of the 41 priority substances, indicating a first success of the implementation of the WFD in the investigated river basins.     

Application of two-stage fuzzy set theory to river quality evaluation in Taiwan

An indicator model for evaluating trends in river quality using a two-stage fuzzy set theory to condense efficiently monitoring data is proposed. This candidate data reduction method uses fuzzy set theory in two analysis stages and constructs two different kinds of membership degree functions to produce an aggregate indicator of water quality. First, membership functions of the standard River pollution index (RPI) indicators, DO, BOD(5), SS, and NH(3)-N are constructed as piecewise linear distributions on the interval [0,1], with the critical variables normalized in four degrees of membership (0, 0.33, 0.67 and 1). The extension of the convergence of the fuzzy c-means (FCM) methodology is then used to construct a second membership set from the same normalized variables as used in the RPI estimations. Weighted sums of the similarity degrees derived from the extensions of FCM are used to construct an alternate overall index, the River quality index (RQI). The RQI provides for more logical analysis of disparate surveillance data than the RPI, resulting in a more systematic, less ambiguous approach to data integration and interpretation. In addition, this proposed alternative provides a more sensitive indication of changes in quality than the RPI. Finally, a case study of the Keeling River is presented to illustrate the application and advantages of the RQI.     

Water quality control in the river Arno

In this work, we analyzed pollution in the river Arno using a non-steady advection-dispersion-reaction equation (ADRE) calibrated on experimental data. We examined the influence different pollution control strategies have on dissolved oxygen (DO). We considered (i) flow rate variation; (ii) local oxygenation at critical points; (iii) dynamic modification of wastewater load. Results indicate first, that reservoir management is effective in reducing pollution; second, that local oxygenation is necessary to ensure that DO does not fall below safety levels; and finally, that tuning wastewater loads appears to be impractical to manage the river quality given the stringent limitations it would impose on the industrial effluents.     

Comparative temporal ecotoxicological study in a river basin influenced by petrochemical industries

An approach was developed to evaluate ecotoxicological effects in river basins impacted by anthropic industrial discharges. Genotoxicity was the first level of evaluation of the river water, but when cytotoxicity was associated with genotoxic effects, our research group added chronic assays allowing the assessment of the ontogenic cycle in environmental diagnosis. The genotoxicity of river water sampled during two periods was compared using the microscreen phage-induction and Salmonella/microsome assays. The study assessed the ability of these assays to diagnose environmental quality in an area where petrochemical impacts occur. The study was performed at six sampling sites using the Salmonella/microsome assay for 10 sampling periods and the microscreen phage-induction assay for 15 samplings. The percentage of mutagenic activity was higher at the sites sampled in front of the petrochemical complex in both periods, but there were more significant mutagenic responses in the first assessment. However, comparing the percentages of samples with mutagenic and cytotoxic activity observed during the two periods it becomes clear that there are more cytotoxic samples during the second period throughout the area studied. The genotoxic activity analyzed by the microscreen phage-induction assay was constant in the second period. Chronic toxicity studies with the microcrustacean Daphnia magna confirm the toxic effects observed. The mortality of individuals was higher at the site most influenced by the petrochemical complex, followed by the station located upstream from this area, while the formation of ephippial eggs was uniform at all stations. The rise in the toxic potential of the region detected by cytotoxic and chronic toxicity may interfere and probably impair the use of the Salmonella/microsome assay to determine the potential of the area, showing the importance of assay association to evaluate potentially contaminated areas.     

Analysis of photosynthetic activity in the most polluted stretch of river Ganga

As a result of the increasing anthropogenic activities in the gangetic plain, Ganga water quantity as well as quality has declined over the years. A major effort to clean Ganga, named Ganga Action Plan (GAP) was instituted by the Government of India in 1984. The emphasis in GAP was on the reduction of organic load on the river through interception, diversion and treatment of wastewater reaching the river, thus maintaining the biochemical oxygen demand (BOD) and dissolved oxygen (DO) levels of river within the acceptable limits. A major criticism of GAP is that the significance of river ecology has not been addressed adequately during its conception and implementation. One of the important aspects from this perspective is the photosynthetic activity in the river Ganga. It has been postulated that photosynthetic activity plays an important role in maintaining high levels of DO in Ganga, and as a result the river can assimilate high organic loads without appreciable depletion in dissolved oxygen levels. Objective of the present study was to assess the photosynthetic activity and oxygen production rates in the river and correlate these values with various water quality parameters. Most polluted stretch of Ganga, which is known as the Kannauj-Kanpur stretch was chosen for this study. Based on the results of the study, it was concluded that despite implementation of phase I of GAP, and consequent diversion and reduction of organic loading to the river, both BOD and DO levels in the river has increased in the entire Kannauj-Kanpur stretch, except at Jajmau, where anaerobically treated effluent is discharged to the river. The nitrogen levels have also increased in the entire Kannauj-Kanpur stretch. Dissolved oxygen (DO) and alkalinity in the river water vary diurnally at all sites. Chlorophyll-a levels and oxygen production rates due to photosynthesis appear to be positively influenced by phosphate levels in the river water. Chlorophyll-a levels appear to be negatively correlated to the Ammonical and total Total Kjeldahl Nitrogen (TKN) content in the river water, suggesting the possibility of release of nutrients due to algal death and decomposition under certain circumstances.     

Environmental risk of dissolved oxygen depletion of diverted flood waters in river polder systems - A quasi-2D flood modelling approach

River polders are retention basins contained by levees alongside rivers into which water from the main river channel is diverted during extreme floods in order to cap the peak discharge of the flood hydrograph and to alleviate downstream flood risk by reducing the water levels. The retained water, however, is stagnant and the organic material in the water and the bottom sediments imposes a strong oxygen demand on the water. This paper presents a quasi two-dimensional computer-based methodology to assess the environmental risk exhibited by the operation of polders with which the concentration of dissolved oxygen in river and polder water can be simulated. A Monte-Carlo analysis allows the probability distribution of all the outcomes of the minimum dissolved oxygen levels in the water to be derived. From this analysis, the environmental risk of the dissolved oxygen concentrations in the polder water falling below 2 mg O₂/L (the level considered critical for aquatic ecosystems) can be determined.The August 2002 extreme flood event on the Elbe River, Germany, with a proposed polder system variant was used to calibrate the model. A daily time step was used to for the simulations for a time frame 12-21 August 2008. The results show plausible spatial and temporal variations in the dissolved oxygen concentrations within the polders. The quasi-2D approach was successful in simulating the spatial distribution of water quality constituents in the polder system. There is up to approximately 20% risk that dissolved oxygen levels fall below 2 mg/L in the polders. This risk can potentially increase if sediment oxygen demand increases due to crop residue and water temperatures in polders increase. High nutrient transport in the river during flooding can cause a spurt of phytoplankton growth in the polders.     

Evaluating river water quality through land use analysis and N budget approaches in livestock farming areas

This study was carried out to evaluate the quality of river water by analysis of land use in drainage basins and by estimating the N budgets. The drainage basins of Shibetsu River (Shibetsu area) and Bekkanbeushi River (Akkeshi area) in eastern Hokkaido, Japan were selected for a case study, and the evaluation of water quality was up-scaled to the regional level in Hokkaido by using the Arcview/GIS and statistical information. Water sampling was carried out in August 2001 and May 2002 in the Shibetsu and Akkeshi areas, respectively. The proportions of major land uses in drainage basins such as upland field, forest, urban area, wetland and wasteland for each sampling site were estimated by using topographic maps scaled at 1:25,000. The linear regression results showed that the correlation between NO3-N concentration and the proportion of upland in the drainage basins was highly and positively significant for both the Shibetsu area (r = 0.84, n = 57) and the Akkeshi area (r = 0.71, n = 73) at < 0.001 significance level. The regression coefficients or impact factors of river water quality were 0.015 and 0.0052 for the Shibetsu and Akkeshi areas, respectively. A comparison of these results with that of the previous study results in Hokkaido indicated that the impact factors were highest for intensive livestock farming areas (0.040), medium for mixed agriculture and livestock farming (0.020-0.030), and the lowest for grassland-based dairy cattle and horse farming areas (0.0052-0.015). The results of a simple regression analysis showed that the impact factors had a significant positive correlation with the cropland surplus N (r = 0.93, P < 0.01), chemical fertilizer N (r = 0.82, P < 0.05), and manure fertilizer N (r = 0.76, P < 0.05), which were estimated by using the N budget approach. Using the best-correlated regression model, impact factors for all cities, towns and villages of the Hokkaido region were estimated. The NO3-N concentrations for all major rivers in Hokkaido were predicted by multiplying the estimated impact factors by the proportion of uplands. The regression analysis indicated that the predicted NO3-N concentrations were significantly correlated (r = 0.62, P < 0.001, n = 203) with the measured NO3-N concentrations, reported previously. It can be concluded that estimating the proportions of upland fields in drainage basins, and calculating cropland surplus N enables us to predict river water quality with respect to NO3-N concentration.     

NOM degradation during river infiltration: Effects of the climate variables temperature and discharge

Most peri-alpine shallow aquifers fed by rivers are oxic and the drinking water derived by riverbank filtration is generally of excellent quality. However, observations during past heat waves suggest that water quality may be affected by climate change due to effects on redox processes such as aerobic respiration, denitrification, reductive dissolution of manganese(III/IV)- and iron(III)(hydr)oxides that occur during river infiltration. To assess the dependence of these redox processes on the climate-related variables temperature and discharge, we performed periodic and targeted (summer and winter) field sampling campaigns at the Thur River, Switzerland, and laboratory column experiments simulating the field conditions. Typical summer and winter field conditions could be successfully simulated by the column experiments. Dissolved organic matter (DOM) was found not to be a major electron donor for aerobic respiration in summer and the DOM consumption did not reveal a significant correlation with temperature and discharge. It is hypothesized that under summer conditions, organic matter associated with the aquifer material (particulate organic matter, POM) is responsible for most of the consumption of dissolved oxygen (DO), which was the most important electron acceptor in both the field and the column system. For typical summer conditions at temperatures >20 °C, complete depletion of DO was observed in the column system and in a piezometer located only a few metres from the river. Both in the field system and the column experiments, nitrate acted as a redox buffer preventing the release of manganese(II) and iron(II). For periodic field observations over five years, DO consumption showed a pronounced temperature dependence (correlation coefficient r = 0.74) and therefore a seasonal pattern, which seemed to be mostly explained by the temperature dependence of the calculated POM consumption (r = 0.7). The river discharge was found to be highly and positively correlated with DO consumption (r = 0.85), suggesting an enhanced POM input during flood events. This high correlation could only be observed for the low-temperature range (T < 15 °C). For temperatures >15 °C, DO consumption was already high (almost complete) and the impact of discharge could not be resolved. Based on our results, we estimate the risk for similar river-infiltration systems to release manganese(II) and iron(II) to be low during future average summer conditions. However, long-lasting heat waves might lead to a consumption of the nitrate buffer, inducing a mobilization of manganese and iron.     

潮河流域水质分析研究

指出潮河是密云水库支柱水源，潮河的水质关系到北京人民的身体健康，采用“水质综合评价法”对潮河水质进行了分析，结果表明潮河上游水质状况良好，适合作为城市水源地水源。     

长江与黄河两大流域水生态问题剖析

对流域水生态的研究由传统单一的水质评价逐渐转变为河流生态质量的评价,基于河流健康保障的流域生态保护与发展已成为国际性趋势。长江、黄河两大流域内的生态保护与发展也是重大国家战略。以长江、黄河两大流域为研究对象,对两大流域水生态环境问题进行分区概述,并从河流湖库问题治理的关键是注重流域的整体性的角度,分析为维系两大流域水生态健康可开展的研究工作,最后将生态修复与景观设计结合考虑,提出注重景观价值的流域生态保护策略。     

Interactive fuzzy optimization for an economic and environmental balance in a river system

An interactive fuzzy approach is applied to develop a water quality management plan in a river basin for solving multi-objective optimization problems involving vague and imprecise information related to data, model formulation, and the decision maker's preferences. This approach, originally proposed by Sakawa in 1983, is modified and presented as a sustainable water quality management strategy in which the decision makers and the environmental analysts put forward their views on three major economic and environmental factors: river water quality, assimilative capacity, and treatment cost of wastewater. This methodology is illustrated in a case study of multi-objective water quality management in the Tou-Chen River Basin in northern Taiwan. The incorporation of these three economic and environmental factors demonstrates the capability of the fuzzy interactive multi-objective optimization approach and also works suitably in water quality management in a river basin by the trade-off procedures.     

Algal diversity in relation to water quality in an Indian river

The application of the two diversity indices (Shannon's index of diversity and Margalef s index of diversity) has been critically analysed for water pollution monitoring in the tropical polluted river Khan. These two indices can be usefully employed for the biological assessment of water quality in tropical polluted rivers.     

Parameter optimization of the QUAL2K model for a multiple-reach river using an influence coefficient algorithm

An influence coefficient algorithm and a genetic algorithm (GA) were introduced to develop an automatic calibration model for QUAL2K, the latest version of the QUAL2E river and stream water-quality model. The influence coefficient algorithm was used for the parameter optimization in unsteady state, open channel flow. The GA, used in solving the optimization problem, is very simple and comprehensible yet still applicable to any complicated mathematical problem, where it can find the global-optimum solution quickly and effectively. The previously established model QUAL2Kw was used for the automatic calibration of the QUAL2K. The parameter-optimization method using the influence coefficient and genetic algorithm (POMIG) developed in this study and QUAL2Kw were each applied to the Gangneung Namdaecheon River, which has multiple reaches, and the results of the two models were compared. In the modeling, the river reach was divided into two parts based on considerations of the water quality and hydraulic characteristics. The calibration results by POMIG showed a good correspondence between the calculated and observed values for most of water-quality variables. In the application of POMIG and QUAL2Kw, relatively large errors were generated between the observed and predicted values in the case of the dissolved oxygen (DO) and chlorophyll-a (Chl-a) in the lowest part of the river; therefore, two weighting factors (1 and 5) were applied for DO and Chl-a in the lower river. The sums of the errors for DO and Chl-a with a weighting factor of 5 were slightly lower compared with the application of a factor of 1. However, with a weighting factor of 5 the sums of errors for other water-quality variables were slightly increased in comparison to the case with a factor of 1. Generally, the results of the POMIG were slightly better than those of the QUAL2Kw.     

An advanced modelling tool for simulating complex river systems

The present paper describes MOHID River Network (MRN), a 1D hydrodynamic model for river networks as part of MOHID Water Modelling System, which is a modular system for the simulation of water bodies (hydrodynamics and water constituents). MRN is capable of simulating water quality in the aquatic and benthic phase and its development was especially focused on the reproduction of processes occurring in temporary river networks (flush events, pools formation, and transmission losses). Further, unlike many other models, it allows the quantification of settled materials at the channel bed also over periods when the river falls dry. These features are very important to secure mass conservation in highly varying flows of temporary rivers. The water quality models existing in MOHID are base on well-known ecological models, such as WASP and ERSEM, the latter allowing explicit parameterization of C, N, P, Si, and O cycles. MRN can be coupled to the basin model, MOHID Land, with computes runoff and porous media transport, allowing for the dynamic exchange of water and materials between the river and surroundings, or it can be used as a standalone model, receiving discharges at any specified nodes (ASCII files of time series with arbitrary time step). These features account for spatial gradients in precipitation which can be significant in Mediterranean-like basins. An interface has been already developed for SWAT basin model.     

Empirical evaluation of river basin sustainability affected by inter‐basin water transfer using composite indicators

In this study, a practical approach to evaluate the sustainability of river basins subjected to an inter‐basin water transfer project is developed. Selection of appropriate evaluation indicators is pivotal to such approach. To make use of huge amount of data, composite indicators of sustainability (CIS) should be utilised. The proposed approach relies on 15 sustainability indicators (SI) that cover three major criteria namely (economic, social and environmental), and aggregates them into eight different types of sustainability indices for a more robust outcome. Two scenarios were considered within the source and recipient basins. Furthermore, multivariate principal component analysis (PCA) was applied to determine principal and non‐principal indicators for the two river basins. The ability of CIS and PCA methods were verified via correlation and simple regression methods respectively. The results demonstrated that inter‐basin water transfer may improve sustainability, provided that a proper water resource management is enforced.     

Selecting analytical target pesticides in monitoring: Sensitivity analysis and scoring

Measuring river water concentrations of all pesticides applied in a catchment area is a daunting task. This study aims to develop new score tables for selecting analytical target pesticides. Sensitivity analyses were conducted using a diffuse pollution hydrologic model to quantitatively evaluate the influence of pesticide properties (e.g., log K_OC, degradability [half-life]) on concentrations of rice-farming pesticides in river water. Using the results of the analyses, score tables were systematically designed for the pesticide properties such that the sum of the scores for a particular pesticide, designated as the contamination index, was proportional to the expected/predicted concentration of that pesticide in river water. The contamination indexes for pesticides applied in three river basins were calculated and compared with the corresponding observed pesticide concentrations. Correlations between contamination indexes and observed concentrations were fairly good. Pesticides were ranked according to the quotients obtained by dividing the pesticide concentrations predicted from the contamination indexes by the corresponding drinking-water quality guideline values, and pesticide candidates to be monitored were successfully selected on the basis of a threshold quotient.     

Direct measurement of oxygen in river substrates

A study was conducted to establish if river substratum dissolved oxygen (DO) could be measured directly. Hitherto, such measurements have been carried out by proxy and indirect methods or by direct methods following installation of cores/tubes into the streambed. Redox potential (Eh) readings were also taken at most of the sites for comparison. The overall conclusion is that a reliable, off‐the‐shelf instrumental method of directly measuring DO in river substrates has been tested in laboratory and field conditions. The Eh meter, per contra, did give aberrant results for some measurements particularly in the field but had the advantage of a slimmer probe for easier penetration into substrata. The measurement technique, to determine river interstitial sediment O₂, is a simple and quick direct in situ method that produces reliable results.     

A model for predicting chloride concentrations in river water in a relatively unpolluted catchment in north-east Scotland

The River Dee is an oligotrophic soft water system, in the NE of Scotland, with a catchment area of approximately 2100 km2. The river rises in the Cairngorm Mountains and enters the North Sea at Aberdeen, approximately 140 km from its source. Water chemical quality data was collected every 2 weeks over 12 months for 59 sites distributed throughout the catchment. River water chloride concentrations increased significantly from west to east. In depth investigation of the relationship with distance from the coast revealed the significant difference in spatial distribution of river water chloride concentrations between upland and lowland/agricultural areas, suggesting the possible importance of agricultural practices to streamwater chloride concentrations. Thirty of the sample sites are independent and have been used to develop a simple model for prediction of streamwater Cl- concentration throughout the catchment. The model has been validated using data from the remaining sub-catchments. The model shows that mean Cl- concentration may be reliably predicted from distance from the coast and the percentage of improved grassland and arable land cover in each sub-catchment (r2 = 0.98). It is postulated that the land use effects may be partly due to the evolved link between landuse and catchment altitude characteristics, rather than just the direct effect of applied potassium chloride fertiliser on agricultural land. It was noted that there was insufficient forestry within the River Dee Catchment to reliably include % forest cover in the model.     

Deoxygenation in a mobile-bed river—II. Model calibration and post-audit

Benthic metabolism accounts for over 90% of oxygen uptake in the Tarawera, a mobile-bed river receiving treated pulp mill effluent. A steady-state DO model was developed in 1984 which uses zero-order kinetics for benthic metabolism. During calibration a strong linear relationship was identified between the river deoxygenation rate (benthic oxygen uptake rate) and the river BOD concentration just below the main outfall. When tested against non-steady monitoring data the model successfully predicted monthly-average DO concentrations but tended to “overshoot” when waste loads varied. This suggests that the mobile-bed communities have some ability to attenuate the effects of varying waste loads. A post-audit of the model using recent monitoring data shows that the model can predict day-to-day variations of DO under average waste loading conditions but not when there are sudden large changes of waste load. It can be inferred that there are two different time scales operating: surface microbial communities respond quickly (1–2 days) to variations in waste load, but following a major reduction in waste load, reworking of deeper sediments depresses river DO for several weeks. There is a need to develop “biofilm” type models of mobile-bed rivers in order to refine predictions of DO under non-steady waste loadings.