Contribution of different sources to the pollution of wet weather flows in combined sewers

Experiments performed on "Marais" catchment, in central Paris, aimed to follow up the quality of wet weather flows from the entry to the exit of a combined sewer network. SS, VSS, COD, BOD5, Cd, Cu, Pb, Zn concentrations were measured for an important number of rain events in roof, yard, street runoff, as well as in dry and wet weather flows at the catchment outlet. Mass entry-exit totals, at the scale of the catchment, were calculated over 31 rain events in order to evaluate the contribution of different types of runoff, of sanitary sewage and of sewer sediments to the total wet weather pollutant loads at the catchment outlet. The erosion of in-sewer pollutant stocks was found to be the main source of particles and of organic matter in wet weather flows, whereas heavy metal loads mainly originated from roof runoff, due to the corrosion of metallic roofs. Particles eroded inside the sewer during rain events were found to be quite different from the particles constituting the main part of sewer sediments: they are organic and biodegradable, with rather important settling velocities and seem to accumulate during dry weather periods. A change of the chemical form of heavy metals was noticed during the transport in the sewer and it is suspected that a fraction of the dissolved metals from the runoff is adsorbed on sewer sediments.     

Trace element carriers in combined sewer during dry and wet weather: an electron microscope investigation

The nature of trace element carriers contained in sewage and combined sewer overflow (CSO) was investigated by TEM-EDX-Electron diffraction and SEM-EDX. During dry weather, chalcophile elements were found to accumulate in sewer sediments as early diagenetic sulfide phases. The sulfurization of some metal alloys was also evidenced. Other heavy metal carriers detected in sewage include metal alloys, some iron oxihydroxide phases and neoformed phosphate minerals such as anapaite. During rain events, the detailed characterization of individual mineral species allowed to differentiate the contributions from various specific sources. Metal plating particles, barite from automobile brake, or rare earth oxides from catalytic exhaust pipes, originate from road runoff, whereas PbSn alloys and lead carbonates are attributed to zinc-works from roofs and paint from building siding. Soil contribution can be traced by the presence of clay minerals, iron oxihydroxides, zircons and rare earth phosphates. However, the most abundant heavy metal carriers in CSO samples were the sulfide particles eroded from sewer sediments. The evolution of relative abundances of trace element carriers during a single storm event, suggests that the pollution due to the "first flush" effect principally results from the sewer stock of sulfides and previously deposited metal alloys, rather than from urban surface runoff.     

An inventory of heavy metals inputs to agricultural soils in England and Wales

An inventory of heavy metal inputs (Zn, Cu, Ni, Pb, Cd, Cr, As and Hg) to agricultural soils in England and Wales in 2000 is presented, accounting for major sources including atmospheric deposition, sewage sludge, livestock manures, inorganic fertilisers and lime, agrochemicals, irrigation water, industrial by-product 'wastes' and composts. Across the whole agricultural land area, atmospheric deposition was the main source of most metals, ranging from 25 to 85% of total inputs. Livestock manures and sewage sludge were also important sources, responsible for an estimated 37-40 and 8-17% of total Zn and Cu inputs, respectively. However, at the individual field scale sewage sludge, livestock manures and industrial wastes could be the major source of many metals where these materials are applied. This work will assist in developing strategies for reducing heavy metal inputs to agricultural land and effectively targeting policies to protect soils from long-term heavy metal accumulation.     

Preliminary Analysis Of Heavy Metals In The Kahrizak Landfill Leachate: A Conceptual Approach

No data have been published on the leachate quality for the Kahrizak landfill site, including heavy metal concentrations. Therefore concentrations of Cu, Zn, Pb, Cd, Ni, Co, Fe and Mn were measured in four fresh and older leachate samples during a 10 months period. Conceptually, heavy metals can be considered to be present in three phases: ( a ) Dissolved; ( b ) adsorbed onto suspended solids; and ( c ) adsorbed onto the suspended solids with particle sizes less than 0.45 w m. A method is proposed in this paper to measure the concentrations of heavy metals in each of the three phases. Other samples were analyzed for phases ( a ) and ( b ). Fresh leachate samples with lower pH values had higher dissolved concentrations of heavy metals than the older leachate samples with higher pH values. Particulate heavy metal concentrations were slightly lower at higher pH values.     

The relation between heavy metals and particle size fractions within the severn estuary (U.K.) inter-tidal sediments

Samples of Severn Estuary (U.K.) inter-tidal sediments were fractionated into a range of particle sizes. The heavy metal concentrations in the non-residual portion (acid leach) of the sediment increased with decreasing particle size. However, the general trend was upset by a large proportion of coal particles from the adjacent S. Wales coalfield, within one specific fraction causing an enhanced heavy metal concentration. There were significant (99% confidence level) correlations between the amount of less than 20 μm material in the sediment and the concentration of Fe, Pb, Cu and Mn; lower, but still significant correlations (95% confidence level) were found for Zn, Cd, Ni and Cr. No significant correlation was found for Co. The ratio of heavy metal associated with the less than 20-μm fraction of the sediment to the metal associated with the unfractionated sediment increased for Cu, Pb, Cd and Zn in the lower part of the estuary.     

Heavy metal removal from waste water from wet lime(stone)—gypsum flue gas desulfurization plants

Waste water from wet lime(stone) gypsum flue gas desulfurization processes for coal-fired boilers contains suspended solids (gypsum, silica, hydroxides of iron and aluminum) and soluble salts (chlorides and sulfates of calcium, sodium and magnesium). Furthermore, small amounts of heavy metals such as As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se and Zn are present in these waste water streams. A treatment method has been developed to remove these heavy metals very efficiently. This method has been based on coprecipitation of metal hydroxides and sulfides. The hydroxide and sulfide precipitates are removed by a coagulation/flocculation technique followed by gravity settling. The coprecipitation can be carried out with sodium hydroxide or with lime. Both cases were investigated in two different pilot plants with synthetically composed waste water and with actual waste water from three different types of wet lime(stone)—gypsum flue gas desulfurization plants (lime—gypsum FGD plants without a prescrubber, one using seawater and another using river water as process water; a limestone—gypsum FGD plant with a prescrubber using river water as process water).     

Cu, Pb and Zn contamination in Nuuanu watershed, Oahu, Hawaii

Trace metal contamination in urban aquatic ecosystems in Hawaii is a significant problem, especially in terms of Cu, Pb, and Zn. These trace metals are linked to automobile usage. An in-depth study was designed to determine the influence of road sediments and storm sewers on bioavailable (0.5 M HCl) trace metal concentrations in bed sediments of Nuuanu stream, Oahu. Lead was the most enriched trace metal in the watershed. Compared to baseline Pb concentrations of <3 mg/kg, road sediments averaged 186 mg/kg, with a maximum value of 3140 mg/kg. Stream bed sediments had average Pb values of 122 mg/kg, with a maximum of 323 mg/kg. Al-normalized enrichment ratios (ERs) for the <63 microm fraction indicated that the watershed was significantly polluted in the lower, urbanized reaches, with maximum ER values of 560 and 94 for Pb in road sediments and stream sediments, respectively. Median ER values for Cu, Pb, and Zn in stream sediments were 2, 36, and 5, respectively. Rainfall events prior to sediment sampling masked any influence that storm sewer outlets might have had on the localized spatial distribution of metals associated with bed sediments. However, there was a general pattern of increasing trace metal concentrations downstream as the fluvial network traversed residential areas and commercial, highly trafficked areas in the lower portions of the watershed.     

Heavy metal pollution profiles of dated sediment cores from hebe haven, Hong Kong

Eight sediment cores from Hebe Haven were collected and studied for metals including Cd, Cr, Cu, Fe, Ni, Pb, Zn and Ca. ²¹⁰Pb and ¹³⁷Cs activities were determined to date the time of deposition of the sediment. Hebe Haven is a yacht area and is close to the urbanized coast with several dyeing factories. Except Cd, the greatest enrichment was found at locations closest to the Ho Chung Stream which carried domestic and industrial wastewater to Hebe Haven. Concentrations as high as 0.930, 120, 131, 42.3 and 50.9 mg/kg were found for Cd, Cr, Zn, Cu and Pb, respectively. The corresponding enrichment factors are 13(Cd), 7.0(Cr), 2.9(Zn), 5.2(Cu) and 2.4(Pb). The extent of pollution diminishes from the riverine source. Cr is a typical example because its enrichment was mostly attributed to the nearby dyeing operation. The distribution of Cd appears more complicated. A maximum concentration of 3.60 mg/kg was found at a location far from Ho Chung Stream and with no nearby municipal or industrial activity. No significant Fe and Ni enrichment was found in the area. Ca in all cores decreases towards the sediment-water interface. It is probable that the abundance of shellfish has decreased as a result of excessive exploitation as seafood and pollution. ²¹⁰Pb activity and heavy metal concentrations of surficial layers have been “diluted” by excessive deposition of Fe-deficient particles. This likely indicates the rapid deposition of coarser and sandy particles during the construction of a nearby large housing estate. Some ²¹⁰Pb activity profiles have periodic low values in deeper layers, which should correspond to events of rapid deposition of erosion during heavy typhoons and rainstorms. Overall, the sedimentation rates calculated were in the range of 0.351–0.561 cm/yr. In one site (Core S4) close to the riverine source and with the best available dating data, the recent anthropogenic fluxes of heavy metals in μg cm⁻² yr⁻¹ are estimated as: 0.081(Cd), 22(Cr), 20(Zn), 6.4(Cu) and 7.4(Pb).     

Modeling heavy metal uptake by sludge particulates in the presence of dissolved organic matter

The uptake of the seven heavy metal ions Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) by sludge particulates in single-metal systems was investigated. Results showed that under acidic and neutral pH conditions, the uptake of all heavy metals by sludge particulates increases with the increase of pH. However, in the alkaline pH region, the uptake of Cu(II), Ni(II), and Co(II) decreases with the increase of pH, primarily due to the high dissolved organic matter (DOM) concentration in high pH conditions. Based on chemical reactions among heavy metal, sludge solids, and DOM, a mathematical model describing metal uptake as functions of DOM and pH was developed. The stability constants of metal–sludge and metal–DOM complexes can be determined using this model in conjunction with experimental metal uptake data. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on March 1997, the stability constants of Cu(II)–sludge complex (log K_S) and Cu(II)–DOM complex (log K_L) are 5.3±0.2 and 4.7±0.3, respectively; for Ni(II), they are 4.0±0.2 and 3.9±0.2, respectively. Results also showed that under neutral and low pH conditions (pH<8), the DOM effects on metal uptake for all heavy metals are insignificant. Therefore, the DOM term in the model can be ignored. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on December 1996, the estimated log K_S values of metal–sludge complexes for Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) are, respectively, 3.6±0.2, 3.0±0.1, 5.5±0.1, 4.8±0.1, 3.1±0.1, 5.1±0.1, and 4.4±0.3.     

Anthropogenic contamination and risk assessment of heavy metals in stream sediments influenced by acid mine drainage from a northeast coalfield,India

The total concentrations and chemical partitioning of heavy metals in streambed sediments, collected around the Jaintia Hills coal deposit of northeast India, were studied using pollution indices and multivariate techniques to evaluate the risk and contamination levels from heavy metals and their possible origins. Results show that sediments close to mining sites have low pH (<4), high organic carbon, and contain significant amounts of Fe-oxyhydroxide phases (mainly, goethite and schwertmannite), which implies direct impact of coal mine drainage. The average concentrations of Fe, Cu, Co, Cd, Cr, and Zn exceeded the World average, and in some cases, Cd, Cu, Ni, and Cr concentrations exceeded the threshold effects level, which suggests they will be toxic to aquatic biota. Contamination factors (CF) show that the sediments are low to highly contaminated with Cd, Cu, Mn, Pb, Fe, and Zn and low to moderately contaminated with Co, Cr and Ni. The pollution load index (PLI), degree of contamination index (C _deg) and Nemerow integrated pollution index (NIPI) show that the sediments are moderately to highly contaminated, with the extent of pollution greatest nearest to the collieries. The potential ecological risk index (RI) shows low to considerable ecological risk from heavy metals in the sediments, with Cd having the high potential of risk, which also agrees with the risk assessment code (RAC). Multivariate statistical analysis suggests that the concentrations of the heavy metals in stream sediments are strongly influenced by Fe-oxyhydroxide phases and organic carbon derived from anthropogenic sources, mainly coal mining activities. Although a significant proportion of the Cd, Mn, and Ni in the sediments are partitioned into exchangeable and organic fractions, a sizable amount of metals are also found in the Fe–Mn fraction, suggesting that Fe-oxyhydroxides play a dominant role in controlling metal mobility in these stream sediments.     

Concentrations of heavy metals and plant nutrients in water, sediments and aquatic macrophytes of anthropogenic lakes (former open cut brown coal mines) differing in stage of acidification.

Concentration of heavy metals (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn) as well as macronutrients (N, P, K, Ca, Mg, S) were measured in water, bottom sediments and plants from anthropogenic lakes in West Poland. The collected plants were: Phragmites australis, Potamogeton natans, Iris pseudoacorus, Juncus effusus, Drepanocladus aduncus, Juncus bulbosus, Phalaris arundinacea, Carex remota and Calamagrostis epigeios. Two reference lakes were sampled for Nymphaea alba, Phragmites australis, Schoenoplectus lacustris, Typha angustifolia and Polygonum hydropiper. These plants contained elevated levels of Cd, Co, Cr, Cu and Mn, and part of the plants contained in addition elevated levels of Mn, Fe, Pb, Ni and Zn. Analyses of water indicated pollution with sulfates, Cd, Co, Ni. Zn, Pb and Cu, and bottom sediments indicated that some of the examined lakes were polluted with Cd, Co and Cr. Strong positive correlations were found between concentrations of Co in water and in plants and between Zn in sediments and plants, indicating the potential of plants for pollution monitoring for this metal. Heavy metal accumulation seemed to be directly associated with the exclusion of Ca and Mg.     

A survey of heavy metals in municipal wastewater in combined sewer systems during wet and dry weather periods

During wet weather, combined sewer system overflows affect the quality of water in watercourses. For planning overflows, the lowest possible load of priority substances according to Directive 2008/105/EC is crucial and the knowledge of variability in concentrations of elements in the sewer system is necessary. The behaviour of heavy metals in a sewer system was observed in the course of dry weather flow (DWF) and wet weather flow (WWF). We found, from the comparison of concentration medians for the WWF and DWF that during wet weather periods, an increase in the concentrations of As, Cr, Cd, Pb, Mn and Fe occurs in the sewer system and the effect of nonpoint sources manifests itself. Zn, Cu and Ni concentrations decreased during wet weather periods, and Hg concentrations did not significantly change. During the WWF period, a considerable nonhomogeneity of the sewage system was demonstrated.     

Total metal concentrations and partitioning of Cd, Cr, Cu, Fe, Ni and Zn in sewage sludge

Application of the BCR three-step sequential extraction procedure to sewage sludge samples collected at an urban wastewater treatment plant (Dom ale, Slovenia) is reported. The total concentrations of Cd, Cr, Cu, Fe, Ni and Zn and their concentrations in fractions after extraction were determined by flame or electrothermal atomic absorption spectrometry (FAAS, ETAAS) under optimised measurement conditions. Total acid digestion including hydrofluoric acid (HF) treatment and aqua regia extraction were compared in order to estimate the efficiency of aqua regia extraction for determination of total metal concentrations in sewage sludge. It was found experimentally that aqua regia quantitatively leached these heavy metals from the sewage sludge and could therefore be applied in analysis of total heavy metal concentrations. The total concentrations of 856 mg kg⁻¹ Cr, 621 mg kg⁻¹ Ni and 2032 mg kg⁻¹ Zn were higher than those set by Slovenian legislation for sludge to be used in agriculture. Total concentrations of 2.78 mg kg⁻¹ Cd, 433 mg kg⁻¹ Cu and 126 mg kg⁻¹ Pb were below those permitted in the relevant legislation. CRM 146R reference material was used to follow the quality of the analytical process. The results of the BCR three-step sequential extraction procedure indicate high Ni and Zn mobility in the sludge analysed. The other heavy metals were primarily in sparingly soluble fractions and hence poorly mobile. Due to the high total Ni concentration and its high mobility the investigated sewage sludge could not be used in agriculture.     

Heavy metal behaviour during the activated sludge process I. Extent of soluble and insoluble metal removal

The extent of removal of Ag, Bi, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Tl and Zn and their distribution between the soluble and insoluble phases in the influent, and effluent of the activated sludge process has been studied using a pilot-scale plant operated at sludge ages of 3, 6, 9 and 12 days. Molybdenum, Tl, Co, Mn and Ni were >50% soluble in the influent settled sewage. The mean removals of the former two metals were <3% and the latter three were 35 and 50%. Silver, Bi, Cd, Cr, Cu, Pb and Zn were all <35% soluble in the influent and had substantial removals of >75%. Solubilities were greater in the effluent than the influent with the exception of Mn. The observed overall removals of Ag, Bi, Co, Ni, Pb, Tl and Zn were almost entirely due to insoluble metal removal; Cd, Cr and Cu removals had a significant contribution from soluble metal removal. Overall Mn removal appeared to be solely due to soluble metal removal.     

The chemical phase changes in heavy metals with drying and oxidation of the lake sediments

In order to understand the effects of oxidation on heavy metal behavior in sediments, the changes in chemical phase distributions of heavy metals with oxidation of sediments from Lake Teganuma were investigated using a sequential chemical extraction procedure for heavy metals.The exposure of sediments from the lake bottom to atmosphere caused the increase of Eh and the decrease of acid volatile-S in sediments. Most of the cadmium is expected to exist as relatively stable forms such as sulfides in original reduced sediments prior to exposure to the atmosphere. With the oxidation of sediments, Cd in the sulfidic/organic fraction were transformed to forms in the exchangeable and the reducible fractions which are easily dissolved. The chemical phase changes of Cu, Pb and Zn in sediments were less drastic than the case of Cd. Cadmium distinctly affected by the change in redox potential in sediments, and its behavior in the oxidized state is most mobile. Compared to Cd, the behavior of Cu and Pb are not so remarkably affected by the change in redox condition of sediments.     

Comparison of sediments and organisms in identifying sources of biologically available trace metal contamination

Sediments and an indicator organism (Macoma balthica, a deposit-feeding bivalve) were used to assess the relative importance of secondary sewage, urban runoff, a landfill containing metal-enriched ash wastes and a yacht harbor in contributing to Ag, Cu and Zn enrichment in South San Francisco Bay. Spatial gradients in sediments and organisms showed Cu and Ag enrichment originated from sewage discharge, whereas Zn enrichment originated from both sewage and urban runoff. Elevated concentrations of Cu in the sediments of the yacht harbor resulted from a high abundance of fine particles. The biological availability of Cu, Ag and Zn did not coincide with metal enrichment in sediments. The availability of Cu and Ag was greatest nearest the sewage outfall and greater in winter and spring than in summer. The availability of Zn in urban runoff appeared to be lower than the availability of Zn associated with sewage.     

Source apportionment of pollutants and flows of combined sewer wastewater

To reduce the combined sewer overflows (CSOs) and improve surface water quality in the Greater Milwaukee area, construction of a 19.5-mile (31.4 km) inline storage system (ISS) was completed in 1994 to capture and convey sanitary sewage and stormwater for treatment. However, one to six overflows per year still occur. Chemical mass balance (CMB) and positive matrix factorization (PMF) modeling was done in order to find origins of flows and pollutants in CSOs. Based on overflow events from 2000 to 2006 (CMB) and 2004 to 2006 (PMF), we found that between 27% and 56% of the total overflow is from sanitary sewage and most of the remaining from stormwater with possible minor contribution (< or = 8%) from groundwater. Most total suspended solids and metals (Cd, Cr, Cu, Pb, Ni, Hg, and Zn) are from stormwater, while sanitary sewage carries large contributions (> or = 28%) of BOD5, NH3, and total phosphorus. The fraction of NH3 is especially high, i.e., > or = 58%. Implications for a possible future sewer separation in combined sewer areas into separate sanitary and storm sewers are discussed.     

Mobilization of heavy metals from Le An River sediment

The release of sediment-bound heavy metals can have a significant influence on river water quality. Generally speaking, variations of pH and oxygen are among the most important chemical factors that affect the mobility of sediment-bound metals. Recent research has indicated that sulfide, measured as acid-volatile sulfide (AVS), is an important partitioning component of heavy metals. We determined the metal release potential of sediments from the Le An River which receives drainage from a major copper mining operation. We found that the in-situ Cu, Pb, Zn, Cd and As concentrations of the Le An River sediments below the mine are much higher than are the global background values, but that Ni was not elevated. There is potential for mobilization of bound metals to the overlying water, the order of metal release ratio in terms of pH dependencies is Zn > Cu > Cd approximately Pb. Sulfide is not a major binding component for metals in Le An River sediment. It is more likely that the iron and manganese oxides are the most important metal binding components in the sediments of the Le An River.     

Heavy metal content of oysters from the Lynher Estuary,U.K.

The concentrations of As, Cd, Cu, Hg, Pb and Zn have been determined in oysters and sediments from the Lynher Estuary, U.K. The sediments contained high levels of Cu, Fe, Pb and Zn probably associated with run off from a metalliferous catchment area and high Hg associated with a local sewage input. In contrast, the analyses of the oyster tissue showed that only Cu and Zn were concentrated in the flesh. The majority of samples contained coliform bacteria in excess of 1000 organisms per ml of tissue. It is concluded that the quality of the oysters from this fishery was limited by the bacteriological cleanliness rather than toxic metal content.     

微波萃取法用于污泥重金属形态的区分

采用Tessier五步萃取法分析城市污水厂污泥中重金属的形态分布,将其分为交换态、碳酸盐态、Fe-Mn氧化态、有机态和残渣态。在前四个阶段将传统的Tessier方式进行了修改,在每一步骤采用微波加热以减少运行时间。在前三态中,Zn、Pb、Ba、Ni以微波方式萃取的结果与传统方式比较接近,但Ni在Fe-Mn氧化态的结果稍微偏低(回收率为81. 24% );Pb在碳酸盐态的结果偏高(回收率为192. 19% );Ba在交换态的结果偏低(回收率为80. 94% );Zn在交换态的结果偏高(回收率为125. 50% )。Cu和Mn在所有形态中的结果都偏低。有机态不同于前三态,萃取效率与传统方法有很大差异。综合考虑各元素在样品中的形态分布情况和总体重金属含量,可知Ni、Ba和Cu在外界环境中活性较小,Mn、Pb和Zn则活性较大。