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This study evaluated the influence of the type and dose of coagulants on the removal of 16 polycyclic aromatic hydrocarbons (PAHs) in the coagulation process. The effects of coagulant type and dose in reducing water turbidity, colour, and the total content of organic compounds were also assessed. The surface water samples had the turbidity of 9.3–11.2 NTU and colour of 25–35 mg/L. The content of organic compounds determined with total organic carbon (TOC) was 9.2–12.5 mg/L. For the coagulation process, pre-hydrolyzed polyaluminium chloride (PACl) coagulants with basicity values of 41%, 65%, and 85% were used. This shows that water purification performance increased as the basicity of the coagulant increased. When the coagulant with the highest basicity and a dose of 3 mg Al per litre was used, a removal efficiency of 83% in the concentration of benzo(a)pyrene was achieved, and efficiencies for the remaining 15 PAHs ranged from 80% to 91%. These values were 4%–9% higher than those achieved using other coagulants. The removal efficiencies of turbidity, colour, and TOC were 80%, 60%, and 35%, respectively. The water purification performance, including PAH removal, was improved with the increased coagulant dose. Increasing the coagulant dose had more pronounced effects on PAH removal than on the reduction of turbidity and TOC.

The aim of the study was to evaluate the effectiveness of the reduction of surface water pollution level in the coagulation process with polyaluminum chloride and coagulation supported by ozonation process. The effectiveness of these processes was evaluated in relation to the decrease in turbidity and color of water, the content of organic compounds (determined by total organic carbon (TOC) and dissolved organic carbon, oxidizability (OXI), ultraviolet absorbance) and the potential for the formation of THM-FP trihalomethanes. The use of pre-ozonation and coagulation with polyaluminum chloride allowed for a reduction in the content of organic matter determined by TOC, OXI, absorbance UV by 28%–38%, 39%–54%, and 48%–73%, respectively. Compared to the effects obtained using only the coagulation process, this was an increase of 4%–8%, 6%–12%, and 10%–18%, for TOC, OXI, and absorbance UV, respectively. The effectiveness of water purification depended on the quality of raw water, month and location of water collection. The potential for THM formation in treated water in the coagulation process was by 50%–56% lower than in untreated surface water after chlorination. The application of additional pre-ozonation resulted in an additional reduction of THM-FP by 1%–10%.

Application of coagulation process in surface water treatment allows for decrease in turbidity and colour of water, as well as organic matter content. The aim of this study was to evaluate the effectiveness of the coagulation process using pre-hydrolyzed salts, polyaluminium chlorides (general formula Aln(OH)mCl3n–m) with different basicity, in reducing the level of pollution of surface water with organic substances. Apart from the typical indicators used to evaluate the content of organic compounds (total organic carbon [TOC], oxidisability [OXI], ultraviolet absorbance [UV254]), the potential for trihalomethanes formation (THM-FP) was also determined. Under the conditions of the coagulation (pH 7.5–7.9, temperature of 20°C–22°C), the best results were obtained using highly alkaline polyaluminium chlorides, decrease in TOC, OXI and UV254by 32%–61% and slightly worse 24%–45% using medium alkaline. Using the low alkaline coagulant, 25%–46% removal of organic matter was obtained. Significant removal of organic compounds in the coagulation process resulted in a decrease in THM-FP value during water chlorination. THM-FP in purified waters was by 41%–65% lower than in untreated surface water subjected to chlorination. The concentration of CHCl3accounted for 86%–94% of the total THM content in the analyzed waters.

AbstractSuitability of powdered activated carbon CWZ-30 for enhancing the coagulation process used for the removal of contaminants from surface water was evaluated. Aluminium sulphate, aluminium chloride and pre-hydrolysed polyaluminium chloride (PAX18 and PAX-XL1905) were used as coagulants, and the following parameters were analysed in water sampled from the Kozłowa Góra dam reservoir (Poland): concentrations of heavy metals (Cu, Cd, Ni, Pb) and indicator PCBs (28, 52, 101, 118, 138, 153, 180). The highest reduction in heavy metal concentration was obtained with the use of PAX-XL1905. It amounted, in case of copper, cadmium, nickel and lead, to 64, 39, 18 and 85%, respectively. Enhancement of coagulation with powdered activated carbon CWZ-30 in the amount of 30 mg L−1, increased the efficiency of these metals removal up to 79, 53, 26 and 95%, respectively. The best results for total PCB concentration removal were obtained with the use of PAX18. Application of powdered activated carbon also allowed to obtain better effects of PCB removal from water. Therefore, the coagulation process enhanced with powdered activated carbon had crucial impact on the reduction of analysed heavy metals concentration and indicator PCBs.

Suitability of powdered activated carbon CWZ-30 for enhancing the coagulation process used for the removal of contaminants from surface water was evaluated. Aluminium sulphate, aluminium chloride and pre-hydrolysed polyaluminium chloride (PAX18 and PAX-XL1905) were used as coagulants, and the following parameters were analysed in water sampled from the Kozłowa Góra dam reservoir (Poland): concentrations of heavy metals (Cu, Cd, Ni, Pb) and indicator PCBs (28, 52, 101, 118, 138, 153, 180). The highest reduction in heavy metal concentration was obtained with the use of PAX-XL1905. It amounted, in case of copper, cadmium, nickel and lead, to 64, 39, 18 and 85%, respectively. Enhancement of coagulation with powdered activated carbon CWZ-30 in the amount of 30 mg L−1, increased the efficiency of these metals removal up to 79, 53, 26 and 95%, respectively. The best results for total PCB concentration removal were obtained with the use of PAX18. Application of powdered activated carbon also allowed to obtain better effects of PCB removal from water. Therefore, the coagulation process enhanced with powdered activated carbon had crucial impact on the reduction of analysed heavy metals concentration and indicator PCBs.

Bottom sediments originating from the Mitręga water reservoir were studied. It was assayed, in what chemical forms heavy metals (zinc, copper, nickel, cadmium and lead) occur in sediments, using the method of sequential extraction BCR. According to the geochemical criteria with respect to the content of Zn, Cu and Ni, the sediments in all measuring points were classified as uncontaminated, however because of the Cd content - as moderately contaminated. The highest Cu and Ni content was found in the sediment collected in the southern part of the reservoir, 15 and 11 mg/kg d.m, respectively. In the case of Zn, Pb and Cd, the sediment collected at the outflow of the Mitręga river was the most contaminated; metal content amounted to 136; 35; 3 mg/kg d.m., respectively. Based on the conducted fractionation of heavy metals, it was found that the potential mobility of metals, hence the possibility of secondary pollution of the reservoir open water, are arranged in the following order: Zn> Cd> Ni> Cu ~ Pb.

AbstractThe aim of the research work was to evaluate the capability of pre-hydrolysed aluminium salts to reduce turbidity, colour and organic matter from surface water. The coagulants used in the study were Al2(SO4)3and hydrolysed polyaluminium chlorides: PAX18, PAX-XL3, PAX-XL10, PAX-XL 19F, PAX-XL1905, PAX-XL61 and PAX-XL69. Using pre-hydrolysed salts—polyaluminium chlorides—made it possible to obtain better effects of surface water treatment compared with the results accomplished with non-hydrolysed aluminium salt (aluminium sulphate). At a dose of 3 mg Al L−1the best effects of turbidity, colour and organic matter removal were obtained using PAX-XL1905, which is polyaluminium chloride of high alkalinity. Under these conditions, 89% reduction in turbidity and 50% in colour was achieved. Moreover, the total organic carbon (TOC) value decreased by 26%. When pH was decreased from 8.2 to 6.2 the effectiveness of TOC removal increased (upto 37%). The addition of powdered activated carbon to water during coagulation did not significantly affect the effectiveness of organic compounds removal.

AbstractTwo digestion processes were conducted: the mesophilic one (as reference system) and the mesophilic one preceded by thermophilic hydrolysis. The production of biogas (methane), was evaluated, as well as the changes in the content of chlorinated biphenyls with codes: 28, 52, 101, 118, 138, 153, and 180, and the changes of heavy metal forms (Zn, Cu, Ni, Pb, Cd, and Cr) in sewage sludge. Higher biogas production, amounted to 1.15 L g−1of removed dry organic matter was obtained during thermophilic–mesophilic digestion, whereas during mesophilic digestion it amounted to 0.78 L g−1; quantity of methane in biogas during both digestions maintained within the range of 61–65%. Sludge hydrolysis accelerated transitions of polychlorinated biphenyls during the mesophilic methane digestion. Twenty-five percent reduction in the indicator polychlorinated biphenyls (PCB) content after the mesophilic digestion was obtained, whereas after digestion preceded by thermophilic hydrolysis—93% decrease in PCB concentration. Lower chlorinated congeners were dominant in fermented sludge. Proceeding sludge digestion promoted the creation of stable chemical forms of heavy metals. Regardless of applied stabilization process, the highest increase in zinc, copper, nickel, cadmium, and chromium content was demonstrated in organic–sulfide fraction, whereas for lead—in the residue fraction.

Two digestion processes were conducted: the mesophilic one (as reference system) and the mesophilic one preceded by thermophilic hydrolysis. The production of biogas (methane), was evaluated, as well as the changes in the content of chlorinated biphenyls with codes: 28, 52, 101, 118, 138, 153, and 180, and the changes of heavy metal forms (Zn, Cu, Ni, Pb, Cd, and Cr) in sewage sludge. Higher biogas production, amounted to 1.15 L g−1of removed dry organic matter was obtained during thermophilic–mesophilic digestion, whereas during mesophilic digestion it amounted to 0.78 L g−1; quantity of methane in biogas during both digestions maintained within the range of 61–65%. Sludge hydrolysis accelerated transitions of polychlorinated biphenyls during the mesophilic methane digestion. Twenty-five percent reduction in the indicator polychlorinated biphenyls (PCB) content after the mesophilic digestion was obtained, whereas after digestion preceded by thermophilic hydrolysis—93% decrease in PCB concentration. Lower chlorinated congeners were dominant in fermented sludge. Proceeding sludge digestion promoted the creation of stable chemical forms of heavy metals. Regardless of applied stabilization process, the highest increase in zinc, copper, nickel, cadmium, and chromium content was demonstrated in organic–sulfide fraction, whereas for lead—in the residue fraction.

The aim of the research work was to evaluate the capability of pre-hydrolysed aluminium salts to reduce turbidity, colour and organic matter from surface water. The coagulants used in the study were Al2(SO4)3and hydrolysed polyaluminium chlorides: PAX18, PAX-XL3, PAX-XL10, PAX-XL 19F, PAX-XL1905, PAX-XL61 and PAX-XL69. Using pre-hydrolysed salts—polyaluminium chlorides—made it possible to obtain better effects of surface water treatment compared with the results accomplished with non-hydrolysed aluminium salt (aluminium sulphate). At a dose of 3 mg Al L−1the best effects of turbidity, colour and organic matter removal were obtained using PAX-XL1905, which is polyaluminium chloride of high alkalinity. Under these conditions, 89% reduction in turbidity and 50% in colour was achieved. Moreover, the total organic carbon (TOC) value decreased by 26%. When pH was decreased from 8.2 to 6.2 the effectiveness of TOC removal increased (upto 37%). The addition of powdered activated carbon to water during coagulation did not significantly affect the effectiveness of organic compounds removal.

AbstractThe aim of this study was to investigate if the combustion of sewage sludge at 600°C (removal of organic matter) can influence the formation of immobile chemical forms of heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr) in ash. Dried sewage sludge samples were collected at two different mechanical–biological wastewater treatment plants. For sewage sludge and residue on ignition (ash) heavy metal speciation analysis according to BCR procedure was conducted. It was demonstrated that metals found in sludge are mainly bound to organic/sulfide fraction. Zinc was present in significant amounts in hydrated iron and manganese oxide fractions, nickel and cadmium in exchangeable-carbonate fraction, and lead in residue fraction. In the ash obtained after calcination at the temperature of 600°C, mainly metal enrichment of nearly insoluble compound fraction (residual fraction) occurred. The content of lead in this fraction was 93–96%. The residual fraction is considered to be chemically stable and biologically inactive. For other metals: zinc, copper, nickel, cadmium, and chromium, their content in the residual fraction was 48–62; 50–68; 69–92; 44–48; and 91–97%, respectively. Metal accumulation in this non-mobile fraction is advantageous with respect to soil–water environment protection.

The aim of this study was to investigate if the combustion of sewage sludge at 600°C (removal of organic matter) can influence the formation of immobile chemical forms of heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr) in ash. Dried sewage sludge samples were collected at two different mechanical–biological wastewater treatment plants. For sewage sludge and residue on ignition (ash) heavy metal speciation analysis according to BCR procedure was conducted. It was demonstrated that metals found in sludge are mainly bound to organic/sulfide fraction. Zinc was present in significant amounts in hydrated iron and manganese oxide fractions, nickel and cadmium in exchangeable-carbonate fraction, and lead in residue fraction. In the ash obtained after calcination at the temperature of 600°C, mainly metal enrichment of nearly insoluble compound fraction (residual fraction) occurred. The content of lead in this fraction was 93–96%. The residual fraction is considered to be chemically stable and biologically inactive. For other metals: zinc, copper, nickel, cadmium, and chromium, their content in the residual fraction was 48–62; 50–68; 69–92; 44–48; and 91–97%, respectively. Metal accumulation in this non-mobile fraction is advantageous with respect to soil–water environment protection.

The aim of the presented research work was to analyze the pollution in the Kozłowa Góra Dam Reservoir (Poland) with indicative Polychlorinated biphenyls (PCBs) (28, 52, 101, 118, 138, 153, 180) and heavy metals (Zn, Cu, Ni, Cd, Pb, Cr). Aluminum sulfate and pre-hydrolyzed polyaluminium chloride (PAX-XL1, PAX-XL19) were used as coagulants, and the following parameters were analyzed in the water samples from the Kozłowa Góra Dam Reservoir: turbidity, color, and concentrations of PCBs and heavy metals (Ni, Cd, Pb). The concentrations of Zn, Cu, Ni, Cd, Pb, and Cr in the water were as follows: 0.022; 0.012; 0.015; 0.01; 0.014; <0.01 mg L-1. The total concentration of PCBs in the water amounted to 6.0 ng L-1. The highest concentration was shown for PCB 28 (1.6 ng L-1), while the lowest concentration was shown for PCB 180 (0.5 ng L-1). After the application of PAX19, polyaluminum chloride with the highest alkalinity, the best results (among the investigated coagulants) for the chosen contaminants’ removal were obtained; 98% decrease of turbidity and 86% lead concentration were acquired. The highest removal rates for the indicator PCBs were obtained using aluminum sulfate. The total concentration of PCBs was reduced by 71%. The removal efficiency for particular congeners ranged from 57% (PCB 28) to 90% (PCB 153).

AbstractThe aim of the presented research work was to analyze the pollution in the Kozłowa Góra Dam Reservoir (Poland) with indicative Polychlorinated biphenyls (PCBs) (28, 52, 101, 118, 138, 153, 180) and heavy metals (Zn, Cu, Ni, Cd, Pb, Cr). Aluminum sulfate and pre-hydrolyzed polyaluminium chloride (PAX-XL1, PAX-XL19) were used as coagulants, and the following parameters were analyzed in the water samples from the Kozłowa Góra Dam Reservoir: turbidity, color, and concentrations of PCBs and heavy metals (Ni, Cd, Pb). The concentrations of Zn, Cu, Ni, Cd, Pb, and Cr in the water were as follows: 0.022; 0.012; 0.015; 0.01; 0.014; <0.01 mg L−1. The total concentration of PCBs in the water amounted to 6.0 ng L−1. The highest concentration was shown for PCB 28 (1.6 ng L−1), while the lowest concentration was shown for PCB 180 (0.5 ng L−1). After the application of PAX19, polyaluminum chloride with the highest alkalinity, the best results (among the investigated coagulants) for the chosen contaminants’ removal were obtained; 98% decrease of turbidity and 86% lead concentration were acquired. The highest removal rates for the indicator PCBs were obtained using aluminum sulfate. The total concentration of PCBs was reduced by 71%. The removal efficiency for particular congeners ranged from 57% (PCB 28) to 90% (PCB 153).

Two types of sewage sludge anaerobic digestion were carried out: mesophilic and thermophilic. Metal speciation analysis was performed revealing some changes in the chemical form of the metals during the stabilization process of sludge. After both methane fermentation processes, a comparable level of organic matter distribution was obtained (≈ 40 %). The amount of produced methane during thermophilic and mesophilic digestion was 560 mL of CH4 and 580 mL of CH4 from 1 g of removed organic matter, respectively. Low concentration of heavy metal ions in the liquid phase of sludge was observed. Metal ions precipitated and remained bound throughout the stabilization process. No accumulation of heavy metals in the mobile fractions of sludge (exchangeable and carbonate) was observed for either digestion process. The highest increase of zinc, copper, nickel, cadmium, and chromium concentration was observed in the organic-sulfide fraction, whereas the highest increase of lead was found in the residual fraction.