Urban Discharges Research Articles

Environmental study of the alternatives for the sewer system of a small coastal community in the bay of biscay

Zumaia is a small tourist community on the northern coast of Spain, situated along the estuary of the Urola river. This ecosystem has been affected by urban discharges coming from the villages surrounding the estuary. According to the 91/271 European Community Directive, regarding wastewater treatment, this situation should be addressed in order to achieve the quality objectives established for the restoration of the natural values of the area. The local Water Authorities of the Basque Country (Spain) have adopted an integrated model for the design of the sewer system of this community. The model was developed specifically for the study of coastal sewerage under dominant wet weather conditions and includes: I) Establishment of the site specific statutory requirements and environmental objectives; 2) Design of sewer system components with specific reference to influences on marine water quality; 3) Development of monitoring programs. The construction of a sewer pipe alongside the river to collect the foul and the stormwater flow will prevent a large proportion of the discharges of contaminants into the receiving waters. However, the presence of overflows in the system during storms leads to the release of a great deal of pollutants into these waters. The main problems related to this type of discharge in the littoral zone arise from the bacteriological contamination of the bathing waters and from the oxygen depletion over the estuary, These two topics have been the predominant issues conditioning the consideration of different schemes of management of the sewer system. The aim of this paper is to analyze, from an environmental point of view, the structural and functional scheme considered for the sewage management of this community.

Organotin in the Tagus estuary

The tri(n-butyl)tin (TBT) moiety has been shown to have complex ecotoxicological effects on estuarine populations. In the Tagus the massive die-off of the Portuguese oyster (Crassostrea angulata Lmk), has been attributed to the introduction and use of this contaminant by shipyards. This paper reviews previous work by others and reassesses our results obtained in water and sediments of the Tagus estuary, as a contribution to the understanding of tin geochemistry and organotin speciation in this estuary. Contrary to earlier results, the latest surveys show that in the open waters of the Tagus measurable concentrations of all the three butyltin species occur, exhibiting peak concentrations at two locations that indicate two previously undetected sources of TBT. TBT also presents a peak concentration in sediments near the Lisnave shipyards, as previously suggested. The latest surveys still detected methylated forms of tin, particularly monomethyltin (Me Sn3+), in Tagus sediments, with maximum concentrations in the vicinity of urban effluent discharges. The concentrations for TBT and its degradation products found in the Tagus are potentially harmful to the populations of gastropods and endemic bivalves.

Optimised lamellae settling process for run off water treatment

Since the more stringent new french standard of the 3rd of January 1992 relating to water and embracing Urban Run Off Water Discharges during wet weather, some research works have been carried out to treat run off water. In particular, processes based on lamellae settler have been studied. The study presented in this paper describes optimal conditions achieved on a lamellae settler prototype and the results obtained. Parameters investigated were as follow:– injection of coagulant (ferric chloride) controlled by the Suspended Solids (SS) flow feeding the lamellae settler– energy input in the flocculator to improve flocs polymerisation– sludge scraped in the thickened area– optimum adjustment of extracted sludge. Sludge recirculation combined with on line monitoring of Suspended Solids in the flocculator allowed the maximum sludge loading to be established. Those optimisations were applied with an hydraulic load of 150 m.h−1. Removal efficiency were 70% for Suspended Solids and 60% for Chemical Oxygen Demand (COD). The concentration of extracted sludge was 30 g.l−1.

Monitoring organic pollution and eutrophication in the Grand River, Ontario, by means of diatoms

Diatom analysis discriminates between the impacts on river water quality of treated urban wastewaters and diffuse nutrient sources from farmland. Evaluation of organic pollution and trophic levels in the Grand River, Ontario, using two diatom indices shows a clear differentiation among 10 sampling sites over a distance of 214 km. Sites in the central reaches that are influenced by both urban discharges and agricultural runoff have the lowest water quality. The ranking of sites according to both diatom indices is consistently independent of substratum and seasonality. Ordination of samples by multivariate analysis results in a primary separation of the spring and summer communities and a secondary separation of upper, central, and lower reaches. Substratum differences are only apparent at the tertiary level, and mainly for midsummer samples from the upper reaches. Canonical correspondence analysis shows that the largest portion of the observed variability in species composition can be explained by a seasonal gradient related to temperature and by longitudinal gradients of nitrate-nitrogen, conductivity, and chloride. Differences in species composition between nutrient-rich sites and polluted sites are identified. Compared with a study conducted in the 1960s, the Grand River shows clear signs of increased eutrophication.

Coprostanol in the Intertidal sediments of Kuwait. case study on urban sewage contamination

The present study was conducted to assess the nature and degree of contamination by urban sewage discharge in the costal zone of Kuwait. Intertidal surface sediments were collected from the vicinity of coastal effluents and bathing beaches. The sediments were characterized for their sterol composition (coprostanol; cholesterol; campesterol; stigmasterol and β‐sitosterol) and total organic carbon content (TOC). The analyses revealed that the fecal biomarker coprostanol is present at levels ranging between 0.55–45.06 μg/g dry weight, which amounted to 9.9–49.45% of the total sedimentary sterols measured. The locus of highest impact is the southwestern edge of Kuwait Bay at Shuwaikh area. This probably resulted from the continuous sewage discharge from effluent, slow speed tidal currents and the nature of sediments. The overall patterns of distribution indicate that the sewage‐derived material discharged from coastal effluent is affected by the physical processes constraining the area. The prevailing tidal currents contribute to fecal contamination of bathing beaches. Significant correlations were found between organic sewage derived materials (coprostanol/total sterol) and TOC. The sterols composition, other than the fecal inputs indicates the contribution of both terrigenous and biogenic inputs to sedimentary organic matter.

Monitoring organic pollution and eutrophication in the Grand River, Ontario, by means of diatoms

Diatom analysis discriminates between the impacts on river water quality of treated urban wastewaters and diffuse nutrient sources from farmland. Evaluation of organic pollution and trophic levels in the Grand River, Ontario, using two diatom indices shows a clear differentiation among 10 sampling sites over a distance of 214 km. Sites in the central reaches that are influenced by both urban discharges and agricultural runoff have the lowest water quality. The ranking of sites according to both diatom indices is consistently independent of substratum and seasonality. Ordination of samples by multivariate analysis results in a primary separation of the spring and summer communities and a secondary separation of upper, central, and lower reaches. Substratum differences are only apparent at the tertiary level, and mainly for midsummer samples from the upper reaches. Canonical correspondence analysis shows that the largest portion of the observed variability in species composition can be explained by a seasonal gradient related to temperature and by longitudinal gradients of nitrate-nitrogen, conductivity, and chloride. Differences in species composition between nutrient-rich sites and polluted sites are identified. Compared with a study conducted in the 1960s, the Grand River shows clear signs of increased eutrophication.

Optimised lamellae settling process for run off water treatment

Since the more stringent new french standard of the 3 rd of January 1992 relating to water and embracing Urban Run Off Water Discharges during wet weather, some research works have been carried out to treat run off water. In particular, processes based on lamellae settler have been studied. The study presented in this paper describes optimal conditions achieved on a lamellae settler prototype and the results obtained. Parameters investigated were as follow: – injection of coagulant (ferric chloride) controlled by the Suspended Solids (SS) flow feeding the lamellae settler – energy input in the flocculator to improve flocs polymerisation – sludge scraped in the thickened area – optimum adjustment of extracted sludge. Sludge recirculation combined with on line monitoring of Suspended Solids in the flocculator allowed the maximum sludge loading to be established. Those optimisations were applied with an hydraulic load of 150 m.h −1 . Removal efficiency were 70% for Suspended Solids and 60% for Chemical Oxygen Demand (COD). The concentration of extracted sludge was 30 g.l −1 .

Detergents and Orthophosphates Inputs from Urban Discharges to Chetumal Bay, Quintana Roo, Mexico

Detergents and Orthophosphates Inputs from Urban Discharges to Chetumal Bay, Quintana Roo, Mexico

The impacts of urban discharges on the hydrology and water quality of an urban watercourse

This paper presents the findings of a study which has investigated the effects of urban discharges upon the hydrology and water quality of a small urban watercourse located in north London. A variety of hydrological variables and water quality parameters were monitored at a site downstream of two surface water outfalls (SWOs) and two combined sewer overflows (CSOs). Precipitation volume was found to be highly correlated with the total storm discharge (r2 = 0.91) and the duration of storm flow (r2 = 0.93). Precipitation intensity displayed a 0.67 level of correlation with peak discharge volume. Aqueous loadings of biochemical oxygen demand (BOD), nitrate, chloride, total ammonia, suspended solids and total and dissolved zinc, copper, cadmium and lead, increased during the five monitored storm events. The highest increases in pollutant loadings compared with dry weather values were associated with BOD and suspended solids.

Evaluation of the roach (Rutilus rutilus)and the perch(Perca fluviatilis)for the biomonitoring of metal pollution

Abstract The bioaccumulation of seven metal cations (Cd, Cr, Cu, Fe, Mn, Pb, Zn) by two species of fish, the roach (Rutilus rutilus) and the perch (Perca fluviatilis), was studied in two stations of the catchment basin of the Seine River. Metal concentrations were twice as high in fish downstream of urban discharges as upstream. The Cu, Fe, Mn and Pb contents were about 1.5 times as high in autumn as in spring. There was no relationship between the metal concentrations and the body size in either species. There was also no evidence of bioamplification revealed by the adjacent trophic levels of the two fish species. Likewise, the metal concentrations in the fish species studied were much lower than those found in a mollusk belonging to the Lamellibranchiates group: the Anodonta cygnea. The roach and the perch are thus reliable animals for the biomonitoring of metal pollution.

Chemical pollution from urban and industrial sewages in Augusta Bay (Sicily)

The Augusta Bay is a complex area where heavy industrialization and dense urbanization have promoted a very high state of degradation. This basin has already been studied for several years because of various eutrophication phenomena which induced a massive fish mortality. In order to deepen our knowledge on the state of chemical pollution due to Dissolved/Dispersed Petroleum Hydrocarbons (DDPH), detergents and N- and P-salts as well as on the eutrophication of the bay, three campaigns have been carried out. The results (from 0.0 to 96.6 μg/l in chrysene equivalents) have indicated that the distribution of DDPH is characterized by an extreme spatial and temporal variability linked to occasional localized spills and to the wind's action which influences the surface water circulation in the bay. The concentration of non ionic (BiAS) and ionic (ABS) detergents averages respectively 63 and 55 μg/l with a predominance of BiAS in the waters affected by the urban discharges, while high ABS values have been also measured in correspondence of a cooling water effluent. Finally, the PO4 (max 0.3 μ/l) and NO2 + NO3 (max 4 μl) levels were relatively low and constant in comparison with previous results, while NH4 remains at a high level (max 14.6 μ/l) with supplies located in the urban discharge as well as in the industrial ones, indicating that both types of effluents are equally responsible for eutrophication and the distrophic crisis observed in the bay.

Urban discharges during wet weather: what volumes have to be treated?

To treat urban wet weather discharges, storage tanks seem to be efficient tools. Using 17 French catchments with an average of one year of measurements, we have estimated the volumes required, at the outlet of the catchments and at the inlet of a tank, to intercept the suspended solids load discharged during several months and during the most polluted events. The results vary widely from one basin to another, between 30 and 150 m3/active ha to intercept 80% of the annual suspended solids load. This does not allow us to draw conclusions about the volumes required in an average situation because rainfall depths and return periods of the rainfall events are different between the catchments. These factors seem to have a big influence on the interception efficiency of the storage tanks. The results can only be seen as representative of the year during which the measurements were taken.

Continuous measurement of pollution due to urban effluents under wet conditions using optical systems

Optical sensors appear well adapted to the pollution measurement of urban discharges during wet weather: they allow a continuous and long time investigation of sudden and highly variable phenomena such as rainfall events. They may also be connected to remote monitoring and sanitary equipment automation systems. This paper deals with the measurement principles and use of this type of equipment: adjustment and calibration, sample collection, equipment maintenance and measurement validation. Taking into account the hydraulicity (flow rate or velocity) allows one to improve appreciably the calibration for runoff waters. Calibration at the laboratory seems better than calibration using registered data on the field, as it makes it possible to eliminate the Suspended Matter under-estimation resulting from sampling/analysis.

Urban discharges during wet weather: What volumes have to be treated?

To treat urban wet weather discharges, storage tanks seem to be efficient tools. Using 17 French catchments with an average of one year of measurements, we have estimated the volumes requited, at the outlet of the catchments and at the inlet of a tank, to intercept the suspended solids load discharged during several months and during the most polluted events. The results vary widely from one basin to another, between 30 and 150 m3/active ha to intercept 80% of the annual suspended solids load. This does not allow us to draw conclusions about the volumes required in an average situation because rainfall depths and return periods of the rainfall events are different between the catchments. These factors seem to have a big influence on the interception efficiency of the storage tanks. The results can only be seen as representative of the year during which the measurements were taken.

Continuous measurement of pollution due to urban effluents under wet conditions using optical systems

Optical sensors appear well adapted to the pollution measurement of urban discharges during wet weather: they allow a continuous and long time investigation of sudden and highly variable phenomena such as rainfall events. They may also be connected to remote monitoring and sanitary equipment automation systems. This paper deals with the measurement principles and use of this type of equipment adjustment and calibration, sample collection, equipment maintenance and measurement validation. Taking into account the hydraulicity (flow rate or velocity) allows one to improve appreciably the calibration for runoff waters. Calibration at the laboratory seems better than calibration using registered data on the field, as it makes it possible to eliminate the Suspended Matter under-estimation resulting from sampling/analysis.

MOUSETRAP — A DETERMINISTIC SEWER FLOW QUALITY MODEL

Recent research into the behaviour of sediments and associated pollutants in sewers has formed the foundation for a dynamic pollutograph-based sewer flow quality simulation model called MOUSETRAP. This is a new component to the MOUSE sewer system hydraulic modelling package. MOUSETRAP has been developed by an international consortium of sewer model developers and users to predict short term variations in sewer flow quality and sediment transport in response to storm events. MOUSETRAP is composed of a series of modules to represent: the quality of surface run off; sediment and pollutant transport, erosion and deposition within pipes; and the biological and chemical processes within the sewer system. By representing the current understanding of real sewer sediments, this new tool gives the user the capability to simulate storm event pollutographs incorporating first foul flush phenomena. The paper describes the basis of the new MOUSETRAP modules. Results of initial theoretical testing and pilot study applications are presented to illustrate the model's capabilities and potential for use in the management of urban wastewater discharges.

The distribution and abundance of urea in tropical estuarine waters in relation to hydrochemical parameters

A field study was conducted to determine the role of hydrochemical influence on the abundance and distribution of urea‐nitrogen in a tropical estuary. The dissolved urea exhibited prominent features of seasonal estuarine build‐up during low flow conditions. At times of high biological production, this parameter was correspondingly lower. The paper further studies the influence of physical factors like temperature and salinity (estuarine hydrography) as well as chemical factors like pH, DO, DOC and Chlorophyll‐a to bring out the associated features. The uptake of urea as a preferred nutrient during biological activity is also reported. Industrial or urban waste discharges did not contribute significantly to the abundance of urea for this part of the waterbody. The tropicality of nutrient cycling as revealed from urea‐nitrogen distribution signatures the phenomenal regional diversity.

Bioaccumulation of heavy metals in flora and fauna of Hooghly estuary, east coast of India

Spectroscopic determinations of Fe, Zn, Mn, Cu, Co and Ni were carried out in 23 organisms including seaweeds, zooplankters, molluscs and fishes from Hooghly estuary at the confluence of Bay of Bengal. Seaweeds and gastropods were more efficient in accumulating levels while zooplankters bivalves and fishes showed intermediate levels. Analyses were performed on the sediment, water and on the individual dissected organs of a mussel, oyster and teleost fish. Bioaccumulation of Fe, Zn, Mn and Cu in the soft body parts (gills, mantle, liver etc.) of the three species showed a high degree of organ specificity in some cases. Major sources of the micropollutants include natural weathering, catchment runoff, urban and industrial discharges that may pose an ecological risk to the local estuarine ecosystem.

Urban Wastewater Discharge and Bacteriological Quality of Receiving Coastal Waters: Processes and Modelling

The aim of this paper is to present some results of bacterial studies which were developed by IFREMER in coastal discharge areas of urban wastewaters; they are focused on the determination of bacterial inputs by wastewater treatment plants, the role of environmental factors on the enteric bacteria survival in the coastal zone, and the modelling of bacteria transport and disappearance in order to provide useful management information for minimizing faecal pollution in the coastal zone.

Variations of Environmental Parameters and Ecological Response in an Urban River

Water and sediment quality deterioration in an urban river was assessed during and after stormwater runoff and sewer overflow. Stormwater runoff bad a noticeable effect on continuous measurements of water quality in the urban river; oxygen sag and increased conductivity was a typical response. Sediment toxicity was found at sites directly exposed to urban runoff, while concentrations of copper and lead exceeded sediment quality criteria. The enzyme activity of the sediment-dwelling bacteria was found to be more sensitive with inhibition downstream and upstream of urban discharge.