Search

The effects of pollutants in runoff on the environment have forced the development of several water treatment systems with the aim of reducing this kind of pollution before its final discharge. Nevertheless, many of these systems do not behave satisfactorily and, additionally, there is a low level of confidence in the treatment performance. This paper introduces the results of research on the long-term performance of a laboratory prototype of a system for catchment, pretreatment, and treatment (SCPT) designed to deal with the polluted runoff water. Solid and oil treatment efficiency were the focus of the study. After 14 consecutive simulated rain events, the treatment efficiency levels achieved by the prototype are higher than 80% of solids and 90% of oils. DOI: 10.1061/(ASCE)EE.1943-7870.0000279 CE Database subject headings: Nonpoint pollution; Runoff; Best Management Practice; Water quality; Catchments. Author keywords: Nonpoint pollution; Runoff; Best management practice; Water quality.

In this research we investigated the ability of cress seeds (Lepidium sativum L.) to grow in an aqueous media with metal toxicities. The toxicity of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn ions were examined in blank, nitrate (N-N[O.sub.3])- , phosphate (K[H.sub.2]P[O.sub.4])-, and saline (NaC1)--contaminated media. The acute toxicity of the tested metal ions in the blank media according to their IC50 (50% inhibitory concentration) values increased on the order of Pb DOI: 10.1061/(ASCE)EE.1943-7870.0000264 CE Database subject headings: Water pollution; Toxicity; Heavy metals. Author keywords: Water toxicity; IC50; Metal ion; Cress seed; Lepidium sativum L.; Root length inhibition.

This paper addresses the issue of contaminated water evacuation as part of the response process in cases of intentional or accidental contamination of drinking water distribution systems (DWDSs). Following a previous study which addressed contaminant isolation, an original flushing procedure (FP) is introduced. Through a heuristic set of rules, the FP defines unidirectional flushing (UDF) strategies in a safe, structured, and efficient manner. In addition to the rather theoretical considerations related to hydraulics modeling, the FP also takes into account the operational issues of UDF implementation. Compared to other similar studies, the latter aspect establishes the main contribution of this paper. The FP has been applied to two real-world networks and application of the heuristic rules is demonstrated with the aid of a detailed example. General results suggest possible improvements to existing network configurations and to the design of projected networks to better support contamination response planning. DOI: 10.1061/(ASCE)WR.1943-5452.0000085 CE Database subject headings: Drinking water; Water distribution systems; Security; Water pollution; Risk management; Flushing. Author keywords: Potable water; Water distribution systems; Security; Contamination; Consequence management; Unidirectional flushing.

A method for optimizing sensor locations to effectively and efficiently detect contamination in a water distribution network is presented here. The problem is formulated and solved as a twin-objective optimization problem with the objectives being the minimization of the number of sensors and minimization of the risk of contamination. Unlike past approaches, the risk of contamination is explicitly evaluated as the product of the likelihood that a set of sensors fails to detect contaminant intrusion and the consequence of that failure (expressed as volume of polluted water consumed prior to detection). A novel importance-based sampling method is developed and used to effectively determine the relative importance of contamination events, thus reducing the overall computation time. The above problem is solved by using the nondominated sorting genetic algorithm II. The methodology is tested on a case study involving the water distribution system of Almelo (The Netherlands) and the potential intrusion of E. coli bacteria. The results obtained show that the algorithm is capable of efficiently solving the above problem. The estimated Pareto front suggests that a reasonable level of contaminant protection can be achieved using a small number of strategically located sensors. DOI: 10.1061/(ASCE)WR.1943-5452.0000073 CE Database subject headings: Optimization; Sampling; Water distribution systems; Water pollution; Risk management. Author keywords: Optimization; Sampling; Water distribution systems; Contamination; Risk analysis.

We compared stable nitrogen isotope ([delta][sup.15]N) values from the common Caribbean sea fan Gorgonia ventalina, collected from a developed and undeveloped coastline, to test the hypothesis that sewage-derived nitrogen (N) inputs are detectable and more severe in developed areas along the Mesoamerican barrier reef of Mexico. The Akumal coast was selected as the developed site since this area is inhabited by thousands of local residents and has a significant flux of tourists; it was compared to a relatively undeveloped shoreline south of Mahahual, a small town with a few hundred residents and sewage treatment infrastructure. Gorgonians sampled from Akumal were relatively enriched in [delta][sup.15]N (as high as 7.7[per thousand] nearshore) and were ~ 3.5[per thousand] greater than sea fans from Mahahual collected at similar depths. While previous work has shown that water column N concentrations are uniform around Akumal, [delta][sup.15]N values of sea fans sampled parallel to shore were variable, indicating that sewage- derived N inputs are spotty along the coast, [delta][sup.15]N values were positively correlated with fecal Enterococcus counts from seawater, confirming that these enrichments are associated with sewage and not denitrification. We suggest that the data from Mahahual can be used as an isotopic baseline for monitoring the Mesoamerican barrier reef at sites where increased development is planned or underway. doi: 10.4319/lo.2010.55.5.2139

If a chemical or biological agent is released into a water distribution system, sensors that are installed in the pipe network may detect the contamination as it travels through the system. To minimize the adverse impact of the contaminant release, the source must be characterized to determine the extent of the contamination and to remediate the contaminated area. We present a backward modeling approach that uses the data collected by the sensors to obtain probability density functions that describe the random time in the past that the observed contamination was at a particular upgradient position. These probability density functions can be used to identify the source node and release time. The approach is developed for steady flow conditions with known system demands and for a single, instantaneous source of contamination. Using a hypothetical water distribution system and release scenario, we demonstrate that the backward model is an efficient and effective approach for identifying the source node and the release time. DOI: 10.1061/(ASCE)WR.1943-5452.0000057 CE Database subject headings: Water distribution systems; Probability; Water pollution; Mathematical models. Author keywords: Water distribution system; Probability density function; Water pollution; Mathematical models.

Groundwater is water present below the surface of the earth in underground streams and aquifers. It is the main source of water supply in arid and semi-arid regions of northwestern China. Studies, in recent years have reported increased cases of aquifer contamination due to different factors such as rapid urbanization and industrialization. Using DRASTIC model, this study attempts to measure vulnerability of ground water to contamination in the Datong Basin, located in Northern China. To reduce subjectivity, a sensitivity analysis was performed to evaluate the influence of a single parameter on aquifer vulnerability. The results show that 32.5% of the total study area is under a 'highly vulnerable zone'. In addition the most sensitive parameter to contamination is aquifer media (A), followed in importance by hydraulic conductivity (C), topography (T), depth to water (D), soil media (S), and impact of vadose zone (I). Net recharge (R) is the least sensitive parameter to pollution. Aquifer vulnerability maps developed in this study are valuable tools for environmental planning and predictive groundwater management. Keywords: Groundwater vulnerability, DRASTIC, GIS, Sensitivity analysis, 1. Introduction Groundwater is the most important source of water supply in arid and semi-arid regions of northwestern China. In recent years, the use of groundwater for water supply in [...]

Problem statement: Debris from construction or demolition/deconstruction processes have no significant impact on the environment as they are res-usable and inert. This has been also long admitted for solid waste generated by the demolition of damaged cities following violent earthquakes. Approach: This study is a contribution to the assessment of actual impact on the quality of groundwater of buried demolition debris from the city of Boumerdes, in the North of Algeria 5 years after the May 21st 2003 earthquake hit the region. The public discharge of Boumerdes city has been used as a temporary landfill. It is located about 5 km downtown of Boumerdes at the Tidjelabine site which is marly-calcareous formation. Leachate from the landfill was directly rejected in the receiving environment, where the soil is marly-calcareous type with cracks giving a variable permeability ([10.sup.-2] m [sec.sup.-1] to nearly [10.sup.-1] m [sec.sup.-1]) that facilitates infiltration of potential pollutants to the groundwater. The slope character (from 5-10%) of the field contributes to pollutants movement and may accentuate water quality deterioration. Three domestic wells (designated S1, S2 and S3) were selected in the vicinity of the landfill and served as piezometers. Leachate samples were taken from the landfill and evaluated. Results: Leachate analysis indicated organic matter with relatively high COD (1136 mg [L.sup.-1] [O.sub.2]) and [BOD.sub.5] (200 mg [L.sup.-1] [O.sub.2]); whereas the pH yielded 7.65 thus indicating fermentation phase of the landfill. Heavy metal contents were beyond national standard limits except for Pb with 0.51 mg [L.sup.-1] which is slightly higher than limit value of 0.5 mg [L.sup.-1]. More than five years after the creation of this landfill and despite its predominant C&D nature, these results showed that it was following a typical urban wastes decomposition scheme. Same analysis carried on water samples drawn from the piezometers yielded following results: acidic pH (6.88), acceptable values of target heavy metals concentrations except for Zn with 0.779 mg [L.sup.-1]. Additionally bacteriological cross analysis (membrane filter and multi-tube methods) showed groundwater contamination by total coliforms (1100/100 mL), fecal coliforms (11/100 mL) and fecal streptococci (1100/100 mL). Conclusion: These results proved that leachate had reached the first aquifer horizon about 10 m beneath soil surface. Prior to any remediation program, Management of Boumerdes Municipality is called to quickly implement a reuse and recycling program of the demolition debris in order to stop water reservoirs contamination source. Key words: Demolition debris, landfill, leachate, heavy metals, groundwater, infiltration, INTRODUCTION The solid waste management is governed by standards the user must respect otherwise they expose themselves to pollution that may follows. For instance, it is common sense, that water [...]