Half-Life of Carcinogenic Polycyclic Aromatic Hydrocarbons in Stored Sewage Sludge
In Poland, according to the statistical data, about 40% of sewage sludges originating from wastewater treatment plants are applied in the agriculture. The mentioned way of application of sewage sludges causes the hazard of contamination of environment with carcinogenic compounds due to the presence of some organic micropollutants, such as polycyclic aromatic hydrocarbons (PAHs). The proposal of changing UE Directive obligates control of organic pollutants (PAHs and others) in sewage sludges applied in the agriculture.
The aim of the investigations was to estimate the persistence of PAHs under stored conditions by determining half-life of their decomposition. Eight carcinogenic PAHs, among 16 compounds, listed by EPA were determined. In this study, the quantity changes in the concentration of PAHs in stored sewage sludges were investigated. Sewage sludges were stored under aerobic conditions for 16 weeks. At the same time the sewage sludges with sodium azide added, in order to deactivate the microorganisms (abiotic samples), were also stored. Gas chromatography-mass spectrometry was used to qualify and quantify PAHs in 2- and 4-week intervals. Sewage sludges were taken two fold from a municipal wastewater treatment plant. In practice, the sewage sludges are directed to the disposal site. The initial concentration of 16 PAHs in sewage sludge was equal to 582 μg/kg.d.m. The changes in the concentration of PAHs corresponded to exponential function. Values of correlation coefficients indicate a significant dependence of PAHs persistence and concentration on time exposition. Under experimental conditions the half-lives of individual compounds were diversed. In biotic samples half-life of hydrocarbons was in the range of 17 to 126 days. Half-life of PAHs in abiotic sewage sludges was in the range of 32 to 2048 days. The most persistent were benzo(a)pyrene and benzo(b) fluoranthene, respectively. A significant dependence of PAHs' decrease on the presence of microorganisms in sewage sludges after 10 weeks of storage was found.
This study focused on the sediment contamination with some organic micropollutants based on the monitoring data together with available literature in Poland. The following persistent organic pollutants (POPs): polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and chlorinated pesticides (CP) were characterized in sediments with respect to current legislations in force. Based on accessible data, higher PAHs, PCBs and CP concentrations were found in river sediments than in lake sediments. Especially, sediments of the Oder River and its tributary in the southern part of Poland, were highly polluted. In order to minimize the risk of the secondary pollution of surface waters, it is necessary to introduce consolidated management system with sediments proceeding. Furthermore, it is also of great importance to elaborate specific regulations concerning conditions of sediments management.
The article presents results on investigation of the removal efficiency of selected 5- and 6-ring polycyclic aromatic hydrocarbons (benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[j]fluoranthene, benzo[g,h,i]perylene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene) from water during coagulation and sedimentation process. Two pre-hydrolyzed aluminum coagulants: PAX XL 19H and FLOKOR 105V were chosen for research. Process was carried out at optimum process parameters: rapid-mixing - 3 min at the rotational speed of 200 rpm, slow mixing - 10 min at 30 rpm, sedimentation - 60 min. The removal effectiveness was dependant on coagulant type and its composition. Better results in the removal of 5-and 6-ring PAHs were obtained after application of FLOKOR 105V (lower aluminum content) than after using PAX XL 19H.
The aim of the investigations was to estimate the half-life of selected PAHs in sewage sludge. Five hydrocarbons selected from 16 PAHs- EPA were chosen. In this study, the quantity changes in the concentration 3- and 4-ring of PAHs in sewage sludges were investigated. Sewage sludges were stored under aerobic conditions for 12 weeks. At the same time the sewage sludges with the added sodium azide, in order to deactivate the microorganisms (abiotic samples), were also stored. Gas chromatography-mass spectrometry was used to qualify and quantify PAHs in 2-week intervals. Sewage sludges were taken from a municipal wastewater treatment plant. Under experimental conditions the half-lives of individual compounds were diversed. In biotic samples halflife of hydrocarbons was in the range of 19 to 368 days. Half-life of PAHs in abiotic sewage sludges was in the range of 31 to 2961 days. The most persistent were phenanthrene.
The aim of the paper was to determine the effectiveness of the removal of 4, 5and 6 - ring PAHs from coking wastewater using sodium percarbonate Na2CO3∙1,5 H2O2 and iron sulphate in acid condition. The samples were exposing to ultraviolet rays. The source of UV-C radiation was a lamp emitting a wave of light with a length of λ = 264 nm, placed directly above the layer of the samples wastewater. The sodium percarbonate Na2CO3 1.5 H2O2 doses were determined on the basis of stoichiometric calculation. Ratio of iron ions to the hydrogen peroxide released in reaction was: 0.5; 0.4; 0.3; 0.2; 0.1. Before and after the oxidation process, COD and TOC value were determined and as well as concentrations of selected PAHs. The total concentration of tested PAHs before oxidation reached the value of 995 μg/L. The average content of organic pollutants determined by the chemical oxygen demand (COD) was 538 mg/L, while the average content of Total organic carbon (TOC) was 180 mg/L. The use of sodium percarbonate caused the oxidation of organic pollutants and lowering of COD and TOC in the following ranges: 22-46% and 10-30%. For individual PAHs the degradation efficiency was in the ranged from 95% to 99.9%. The degradation efficiency of 4 ring hydrocarbons caused 98% and 5 and 6 ring of hydrocarbons was 98.7% and 99.4%, respectively.
At present many WWTPs are focused on increasing quantity of biogas generated during sewage sludge processing. Various disintegration methods can be used for this purpose - thermal heating, ultrasonic disintegration, chemical treatment. The limiting step in sewage sludge digestion is hydrolysis, increasing the rate of this process allows for shortening solids retention time in digester, increasing soluble COD concentration in the reject water and as a result also biogas production. In technical scale ultrasonic and thermal disintegration are used. The most effective are ultrasounds below 100 Hz. In thermal conditioning various technological parameters are applied (from 60 - 80 °C to even 250°C, retention times from 15 min. to 2 hours). Effectiveness of the processes can be increased by using combined processes, e.g. thermal treatment and chemical stabilization. Chemical methods are at present mainly applied in laboratory scale. They include alkaline and acidic pretreatment or advanced chemical oxidation methods.
Currently, organic halogen compounds (halogen derivatives) are often identified in water. The paper presents the problem of the presence of these newly formed compounds during water treatment processes and their occurrence in sewage. The general indicator determining the content of these compounds in aqueous solutions is the concentration of halogen derivatives of organic compounds adsorbed on activated carbon AOX, which is converted to the concentration of chlorides. The groups of derivatives of halogenated organic compounds containing chlorine and/or bromine in a molecule were characterized, and the precursors and potential for the formation of these compounds in water were described. Moreover, technological methods to prevent and remove them were described.
The aim of the investigations was to determine the effectiveness of the removal of 4, 5 - ring PAHs from coking wastewater using dihydrogen dioxide in the presence of a cobalt, platinum or titanium catalyst. A dose 7.4 mL of dihydrogen dioxide in the amount of and 14.8 mL/L of the analyzed sample were added to the samples. The samples were shaken and stored under laboratory conditions for 12 hours. The concentration of PAHs before and after the oxidation process were determined. The quantitative and qualitative chromatographic analysis was carried out using a gas chromatograph coupled with a mass spectrometer (GC-MS). The total concentration of 8 PAHs before oxidation reached the value of 9150 ng/L The concentration of 4-ring compounds and 5-ring PAHs were equal to 6390 ng/L and 2760 ng/L, respectively. The highest decrease (93%) the sum of 8 hydrocarbons using a dose of oxidizer 7.4 ml/L and in the presence of titanium catalyst was achieved.
This article describes the toxicity of organic micropollutants on tested microorganisms. Itis a current issue because organic micropollutants are identified in all elements of environmental (surface water, ground water, soils) and in food products. The organic micropollutants include: polychlorinated dibenzodioxyns PCDD, polychlorinated dibenzofurans PCDF, polychlorinated biphenyls PCB, polycyclic aromatic hydrocarbons PAH, halogenated compounds and by-products of water treatment. Some organic compounds cause hazard for health and human life due to their estrogenic biological activity, carcinogenic, mutagenic or teratogenic activity. The influence on organisms indicators of these compounds based on literature data were presented. The level of TEQ (toxic equivalency) in response to organic chlorine derivatives (PCDDs, PCDF, PCBs) is usually determined by toxic equivalency factor (TEF). The International Agency for Research on Cancer classifies organic micropollutants as carcinogenic to humans (Group 1), possibly carcinogenic (Group 2A) or probably carcinogenic to humans (Group 2B).
This paper presents the results of the possibility and effectiveness of PAHs removal from a model aqueous solution, during the sorption on the selected sorbents. Six PAHs (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene) listed by EPA for the analysis in the environmental samples were determined. Model aqueous solution was prepared with RESTEK 610 mix PAHs standard. After the sorption process, decrease in the concentration of individual hydrocarbons was observed. The removal percentage was dependent on the type of sorbent (quartz sand, mineral sorbent, activated carbon). The highest efficiency (98.1%) was observed for activated carbon.. The results shows that the sorption processes can be used in aqueous solutions treatment procedures.