Maria Włodarczyk-Makuła

THE LOADS OF PAHS IN WASTEWATER AND SEWAGE SLUDGE OF MUNICIPAL TREATMENT PLANT

Abstract Sewage and sewage sludge from a municipal wastewater treatment plant were analyzed for 16 EPA-PAHs. This plant is a classic mechanical-biological treatment plant, consisting of activated sludge technology with additional chemical treatment for the removal of phosphorus compounds. The process of sewage sludge treatment is carried out in closed as well as open sludge digesters. Primary and mechanically thickened sludge are passed through the fermentation process. Digested sludge is dewatered on filter-press through addition of flocculent. The measurements were obtained to investigate the effect of different treatment stages on PAH content in wastewater and sewage sludge. The following wastewater samples were collected: crude ones and those after sand trap, primary sedimentation, biological treatment and secondary sedimentation. Sewage sludge samples were collected from: primary sludge, digested sludge and dewatered sludge. PAH load in influent, mechanically and biologically treated sewage, as well as in raw digested and dewatered sludge, were calculated. PAHs were extracted from wastewater and sludge samples, with cyclohexane, dichloromethane using an ultrasonic method. Gas chromatograph equipped with mass spectrometry was used for qualitative and quantitative determination of PAHs. Mechanical and biological treatment proved the removal of 83–85% of PAHs from the influent. Despite this its daily PAH load introduced into the environment was high and reached 27–37% of PAH load in influent. In sewage sludge it was 46–70 g/d of PAHs (carcinogenic PAHs content 4–12%). In waste sludge (filter pressed sludge and sand from detrirer) PAH total load reached 42–68 g/d with (10–17% of carcinogenic PAHs).

Effectiveness in the Removal of Polycyclic Aromatic Hydrocarbons From Industrial Wastewater by Ultrafiltration Technique

Abstract The paper presents the results of studies on the changes in the PAHs concentration during pre-filtration and ultrafiltration (UF) processes. In the study, biologically treated wastewater (after denitrification and nitrification processes), discharged from the biological treatment plant and used in coke plant, was used. A gas chromatography-mass spectrometry (GC-MS) was used in order to qualify and quantify the PAHs. Sixteen PAHs listed by EPA were determined. The wastewater samples were collected three fold and initially characterized for the concentration of nitrate nitrogen, ammonium nitrogen, COD, TOC and pH. In the first step, wastewater was filtrated on the sand bed. Total concentration of 16 PAHs in the treated wastewater before initial filtration was in the range of 44.8‒53.5 mg/L. During the process the decrease in the concentration of the most studied hydrocarbons was observed. Concentration of PAHs after initial filtration ranged from 21.9 to 38.3 μg/L. After the initial filtration process the wastewater flew to the ultrafiltration module and then was separated on the membrane (type ZW-10). The total concentration of 16 PAHs in the process of ultrafiltration was in the range of 8.9‒19.3 mg/L. The efficiency of removal of PAHs from coke wastewater in the process of ultrafiltration equaled 66.6%. Taking into account the initial filtration, the total degree of removal of PAHs reached 85%. The obtained results indicate the possibility of using the ultrafiltration process with the initial filtration as additional process in the coke wastewater treatment.

Application of UV-rays in removal of polycyclic aromatic hydrocarbons from treated wastewater.

This study was undertaken to investigate the removal of PAHs by UV-rays from treated wastewater. Samples of wastewater originating from a municipal treatment plant were taken twofold (series I and series II). The initial concentration of PAHs ranged: 0.8 μg/L (in series I) and 1.2 μg/L (in series II), respectively. A standard mixture of 16 compounds was added to the wastewater samples. The amount of individual hydrocarbons in the added mixture was equal to 40 μg/L, (in series I) and 50 μg/L, (in series II), respectively. The samples of wastewater without the added standard mixture were treated as a control samples. All samples of wastewater were exposed to UV-rays during 10, 20, 30 and 60 seconds, respectively. Afterwards, the PAHs concentration in both the wastewater samples containing the standard mixture and in the control samples was determined. Determinations of PAHs concentration in wastewater samples in each series were made in triplicates. A quantitative analysis of PAHs was provided by gas chromatography-mass spectrometry (GC-MS). It was found that exposition to ultraviolet rays resulted in the decrease in the concentration of PAHs in the wastewater samples without added standard mixture up to 65%. The efficiency of the removal of hydrocarbons grouped according to a number of rings was in the range of 0 (for 5- ring and 6-ring of PAHs) to 71% (for naphthalene). It was also found that exposure of wastewater samples to UV-rays resulted in a decrease of PAHs concentration in wastewater samples with the added standard mixture up to 84%. The efficiency of the removal of hydrocarbons grouped according to a number of rings differed significantly (to 94% for naphthalene).

Occurrence of heavy metals and PAHs in soil and plants after application of sewage sludge to soil

AbstractThe results of investigations on heavy metals and polycyclic aromatic hydrocarbons (PAHs) content in mixed soil fertilized with sewage sludge are presented. The concentration of these micropollutants in various parts of a basket willow Salix viminalis grown on this substratum was also analyzed. Aerobically stabilized, dewatered, and hygienized sewage sludge (a dose of 90 tons of dry matter per hectare) was used to fertilize the soil. S. viminalis was planted on the soil amended with sewage sludge. The samples for analyses were taken after five vegetatives; they were both soil samples and parts of plants (roots, stems, and leaves). The concentration of heavy metals and PAHs was analyzed in the samples. The concentration of heavy metals in soil after five seasons of fertilizing with sewage sludge was at most cases higher than defined in soil at the beginning of the experiment. The concentration of Cr in soil after five years of S. viminalis cultivation was, however, lower than at the outset. The ave...

Monitoring of Polycyclic Aromatic Hydrocarbons in Water during Preparation Processes

This article presents results on investigation of quantitative changes of polycyclic aromatic hydrocarbons (PAHs) during water treatment processes. PAHs constitute one of several classes of organic pollutants consisting of three or more fused benzene rings. Many of them are quite persistent and some are known to be carcinogens. That is why presentation of quantitative PAHs changes in water during preparation processes is very important. In Polish legislation and European Union law there are recommendations for PAHs concentration in drinking water. The limit value of the sum of 4 PAHs (benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, indeno[1,2,3-cd]pyrene) is 100 ng/L. Limit concentration of benzo[a]pyrene defined in regulations (Polish and UE) is 10 ng/L. The purpose of the present study was to determine changes of concentrations of PAHs in various stages of water treatment process and comparison the values of this index with the limits specified in valid Minister of Health Regulation and Council Directive 98/83/EC. A total concentration of 16 PAHs in the investigated water treatment processes was in the range of 39–204 ng/L. The maximum level was recorded for water after intermediate ozonation. In different water treatment processes were observed fluctuations in PAHs concentrations. Decreased values were recorded among others after pre-ozonation and coagulation and after sedimentation process. Increase of PAHs level occurred after filtration through sand filters. Concentrations of 4 PAHs in drinking water is much below the limit value defined in Polish and UE legislation. Concentration of 16 PAHs in water after final chlorine-disinfection also meets the requirements of the regulation for 4 PAHs.

The Use of Reverse Osmosis in the Removal of PAHs from Municipal Landfill Leachate

Polycyclic aromatic hydrocarbons (PAHs) are relatively well-known organic pollutants and due to their carcinogenic and mutagenic properties their presence in the environment still attracts a lot of attention. According to literature reports and own research, PAHs presence in wastewaters is common. It was confirmed that PAHs are the components of municipal landfill leachate. Membrane techniques are one of the most interesting ways of removing PAHs from leachate. The purpose of this article is to monitor PAHs concentration changes during the membrane (reverse osmosis - RO) leachate treatment processes. In the first stage of testing leachates were filtrated on the sand bed (pre-filtration). After the pre-filtration they were directed to the membrane module for the main filtration. Sixteen PAHs listed by EPA were analyzed. The results with information on PAHs concentration in leachate samples were presented using HPLC with fluorescence detection (FLD). The changes in PAHs concentration were determined in leachate samples before and after pre-filtration as well as after RO. The decrease of PAHs concentration in the samples was observed after these processes. The total concentration of 16 PAHs in raw municipal landfill leachates amounted to 23.64–26.95 μg/L. The research confirmed the high efficiency in removal of PAHs while using a reverse osmosis (59–72%). Including the pre-filtration, the overall level of removed PAHs reached 81–86%. The average PAHs concentration after pre-filtration and RO was in the 4.46–4.99 μg/L range. The municipal landfill leachate with a high concentration of PAHs should be cleaned before it is discharged into the environment.

Comparison of the retention of selected PAHs from municipal landfill leachate by RO and UF processes

AbstractThe aim of the conducted research was to compare the changes in the retention of polycyclic aromatic hydrocarbons (PAHs) during membrane filtration (ultrafiltration—UF and reverse osmosis—RO). In the study, municipal landfill leachate was used. In the first stage of testing, leachates were filtrated on the sand bed (prefiltration). After prefiltration, they were directed to the membrane module for main filtration. The ultrafiltration process was carried out at the transmembrane pressure of 0.1–0.2 MPa. The membrane separation process was based on a capillary membrane type ZW-10. The transmembrane pressure of the reverse osmosis stood at 2 MPa and for this process one nylon membrane (ADF) was used. The prepared samples of the municipal landfill leachates were subjected to extraction with applying 2-propanol. Extracts were cleared on octadecyl C18 columns, and then concentrated in the nitrogen stream. High-performance liquid chromatography HPLC with fluorescence detection (model HPLC THERMO) was use...

PAHs balance in solid and liquid phase of sewage sludge during fermentation process

The results of the quantitative and qualitative analysis of PAHs both in sewage sludge and in supernatants before, during, and after methane fermentation process are presented in this paper. The investigations were carried out under laboratory scale in two series. The sludge samples originated from a municipal treatment plant. The process of fermentation was conducted using batch tests (a one-off batch supplemented with sludges). The content of 16 PAHs, listed by the US EPA, was determined using GC–MS technique. The aim of this investigation was to study changes in contribution groups of hydrocarbons (2-, 3-, 4-, 5-, and 6-ring) in relation to total concentration in PAHs. The objective of these investigations was to follow the changes in the PAHs content not only in sewage sludge (drymass) but also in supernatants (in the liquid phase), and to follow changes in concentration of PAHs during the methane fermentation process as well. The balance of PAHs load in sewage sludge and supernatants mixture was also calculated. An approximate two-fold decrease in dry matter of sludge was observed during the methane fermentation process. During sewage sludge digestion process 3- and 4-ring compounds were released from a solid phase to supernatants.

Degradation of PCBs in sewage sludge during methane fermentation process concerning environmental management

AbstractThe aim of the investigation was degradation of polychlorinated biphenyls (PCBs) in sewage sludge and supernatants during the methane fermentation process. The mixture of municipal sewage sludge and industrial sewage sludge was incubated for 20 d at 37°C in the dark. The quantification of the PCBs was carried out simultaneously in both the solid and supernatant phases, the latter separated from the sludge during centrifugation. The prepared samples of sewage sludge and supernatants were subjected to extraction with the application of the organic solvents mixture. The qualitative–quantitative analysis of PCBs was done using the GC–MS system. After 20 d, the solid phase was observed to have its PCBs content reduced by 58% in the solid phase and 71% in supernatants. The percentage removal of PCBs was 49 and 75% in solid phase and in supernatants mixture of municipal and industrial sewage sludge, respectively.

Desorption of PAHs from solid phase into liquid phase during co-fermentation of municipal and coke sewage sludge

AbstractThe work presents the results of the study that determined the changes in the concentration of polycyclic aromatic hydrocarbons (PAHs) in the sewage sludge and supernatants during the co-fermentation of municipal and coke sewage sludge. The municipal sewage sludge served as a control sample, and the mixture of municipal and coke sewage sludge was used as a test sample. The sewage sludge was incubated for 20 d at 37°C in the dark. The quantification of the PAHs was carried out simultaneously in both the solid and supernatant phases, the latter separated from the sludge during centrifugation. After 20 d, the solid phase was observed to have its PAHs content reduced by 60% in the control sample and 64% in the analyzed one, respectively. The decline in the solid phase PAHs content was accompanied by a significant quantitative increase of the PAHs in the liquid phase, which proves the desorption of solid particles. The control supernatants showed the total concentration of 16 PAHs of 1.1 μg/L prior to ...