Kurzzeit-Toxizitätstests zur Messung der Toxizität von Chemikalien gegenüber Belebtschlamm

Short-term Toxicity Tests for the Measurement of Toxicity of Chemicals Towards Activated Sludge. To avoid severe damage to the activated sludge of a wastewater treatment plant it is necessary to control the sludge activity by means of biological test systems. Especially the short-term respiration assay and the dehydrogenase assay with resazurin as a redox-dye seem to be appropriate for this monitoring program. The practical performance of both test systems was optimized in some essential points. With the help of several reference substances both monitoring systems were tested for practical use as short-term toxicity tests. The results of the investigations showed that the inhibitory concentrations measured in both test systems were partially very different. In monitoring experiments with laboratory-scale wastewater treatment plants it could be shown that a positive correlation between respiration activity and dehydrogenase activity is not always given. Furthermore, a pH-dependent toxicity could be demonstrated for several substituted phenols.     

Anwendung von biologischen Testverfahren an Abwässern der Textilindustrie

Testing Effluents of the Textile Refining Industry with Biological Methods The environmental problems caused by the manufacture of finished textiles involve a long chain of individual processes. This “textile chain” includes very diverse enterprises of varied size and structure. The textile refiners occupy a key position in the “textile chain”. On the one hand, this is due to their use of an obscurely large number of chemicals which can end up in the wastewater as well as in the textile products. On the other hand, this key role of the textile refining industry is based on their central position between the preproduction stage and the consumers. This study dealt with the textile refining industry's wastewater. As measured by volume and contents of its wastewater, this industry can be counted among the major industrial plants which discharge into municipal wastewater treatment plants. German wastewater legislation includes the provision that substances which are toxic, persistent, capable of accumulating, carcinogenic, fetotoxic or mutagenic be kept out of natural waters as well as technically possible (Wasserhaushaltsgesetz WHG). Several biotest methods for examining the effect of the substances contained in the wastewater were incorporated into the appendix of the German wastewater regulation (Rahmenabwasser-Verwaltungsvorschrift based on § 7a WHG). The aim of this study was to show, with the aid of biotest methods, how strongly the wastewater of textile refining companies is polluted as compared to other known industrial branches and to what degree the pollution of these wastewaters is eliminated by the treatment in wastewater treatment plants. Finally, we experimented to find out which biotest methods were suited for the examination of these wastewaters. The study's results show that the ecotoxicity of the textile refining industry's wastewater was only extraordinary high in isolated cases as compared to other examined branches of industry. The textile wastewaters exhibit values of G_L = 3 to G_L = 96 in the luminescent bacteria test, G_D = 1 to G_D = 192 (with one exception of G_D > 30000) in the daphnia test and G_F < = 2 to G_F = 32 in the fish test. It turned out though, that a large number of the samples from the textile refining companies (27%) reacted mutagenically in the Ames test in their native state. Consecutive tests for chromosomal aberrations (V79 hamster cell test) also showed mutagenic potential in five out of nine native samples. The employed testing methods with fish, daphnia and luminescent bacteria demonstrate a higher sensitivity of the luminescent bacteria and/or the daphnia as opposed to the fish in most cases. As the fish test is controversial anyway on the grounds of animal protection, a replacement of the fish test by these other tests should be aimed at: on account of the different end points of the luminescent bacteria and the daphnia test, a combination of these tests appears most sensible.     

Fate of polycyclic aromatic hydrocarbon (PAH) contamination in a mangrove swamp in Hong Kong following an oil spill

The fate of polycyclic aromatic hydrocarbon (PAH) contamination in a mangrove swamp (Yi O) in Hong Kong after an oil spill accident was investigated. The concentrations and profiles of PAHs in surface sediments collected from five quadrats (each of 10 m×10 m) covering different degrees of oil contamination and the most contaminated mangrove leaves were examined in December 2000 (30 days after the accident) and March 2001 (126 days later). The concentrations of total PAHs in surface sediments ranged from 138 to 2135 ng g⁻¹, and PAHs concentrations decreased with time. In the most contaminated sediments, total PAHs dropped from 2135 (30 days) to 1196 ng g⁻¹ (120 days), and the decrease was smaller in less contaminated sediments. The percentage reduction in sediment PAHs over three months (44%) was less significant than that in contaminated leaves (85%), indicating PAH in or on leaves disappeared more rapidly. The PAH profiles were very similar in sediments collected from quadrats Q1 and Q2 with benzo[a]anthracene and pyrene being the most abundant PAH compounds, but were different in the other three quadrats. The proportion of the light molecular weight PAHs to total PAHs increased after three months, especially phenanthrene. Results suggest that physical and photo-chemical weathering (tidal washing and photo-oxidation) of crude oil in surface sediments and on plant leaves were important processes in the first few months after the oil spill. The PAH contamination in Yi O swamp came from both petrogenic and pyrolytic sources. The petrogenic characteristic in the most contaminated sediment was confirmed with high values of phenanthrene to anthracene ratio (>10) and low values of fluoranthene to pyrene ratio (0.3–0.4).     

Aliphatic and aromatic hydrocarbons in marine biota and coastal sediments from the Gulf and the Gulf of Oman

The composition and spatial distribution of aliphatic and polycyclic aromatic hydrocarbons (PAHs) were investigated in biota and coastal sediments from four countries surrounding the Gulf (Bahrain, Qatar, United Arab Emirates and Oman). The levels of total petroleum hydrocarbons (TPH), aliphatic unresolved mixture and PAHs in sediments and biota were relatively low compared to world-wide locations reported to be chronically contaminated by oil. Only in the case of the sediments collected near the BAPCO oil refinery in Bahrain, having concentrations of 779 μg g⁻¹ total petroleum hydrocarbon equivalents and 6.6 μg g⁻¹ ∑PAHs, can they be categorized as chronically contaminated. Some evidence of oil contamination was also apparent in sediments and bivalves around Akkah Head and Abu Dhabi in the UAE, and near Mirbat in Oman. Contaminant patterns in sediments and biota indicated that the PAHs were mainly from fossil sources, with the exception of the high PAH concentrations in sediments near the BAPCO refinery that contained substantial concentrations of carcinogenic PAH combustion products.     

Removal of Aromatic Volatile Organic Compounds in the Sequencing Batch Reactor of Petroleum Refinery Wastewater Treatment Plant

This paper presents a field investigation of aromatic volatile organic compounds (AVOCs) emissions from a sequence batch reactor (SBR) with powdered activated carbon (PAC) to treat the wastewater in a large petroleum refinery plant. AVOC with high Henry's constant preferred to transfer from liquid‐phase into air‐phase so that might cause the emission and odor problem. During SBR operation, AVOC concentrations and distributions in wastewater, sludge and off‐gas were analyzed. The total AVOC removal from wastewater was >99% under the kinetic parameters of SBR operated. Batch experiments were carried out in the laboratory to obtain the adsorptive characteristic of AVOC onto PAC, but the results showed that bio‐degradation was the main removal mechanism (85%). Nevertheless, off‐gas emission (<1%) and AVOC in the sludge (<0.1%) remained a stable level. Oxidation/reduction potential (ORP) was correlated to the logarithm of the dissolved oxygen (DO) concentration in a linear relationship so that ORP profile could indirectly reflect the DO and biomass concentrations. Since the influent AVOC concentration was varied and difficultly to measure, ORP could be used as real‐time parameter for optimizing SBR operation. The results provided useful information for future evaluation of AVOC emissions from wastewater treatment plants.     

Rhizofiltration of a Heavy Metal (Lead) Containing Wastewater Using the Wetland Plant Carex pendula

Rhizofiltration is a subset technique of phytoremediation which refers to the approach of using plant biomass for removing contaminants, primarily toxic metals, from polluted water. The effective implementation of this in situ remediation technology requires experimental as well as conceptual insight of plant–water interactions that control the extraction of targeted metal from polluted water resources. Therefore, pot and simulation experiments are used in this study to investigate the rhizofiltration of a lead containing wastewater using plants of Carex pendula, a common wetland plant found in Europe. The metal contaminant extraction along with plant growth and water uptake rates from a wastewater having varying Pb concentration is studied experimentally for 2 wk. The temporal distribution of the metal concentration in the wastewater and the accumulated metal in different compartments of C. pendula at the end are analyzed using atomic absorption spectrometry. Parameters of the metal uptake kinetics are deduced experimentally for predicting the metal removal by root biomass. Further, mass balance equations coupled with the characterized metal uptake kinetics are used for simulating the metal partitioning from the wastewater to its accumulation in the plant biomass. The simulated metal content in wastewater and plant biomass is compared with the observed data showing a good agreement with the later. Results show that C. pendula accumulates considerable amounts of lead, particularly in root biomass, and can be considered for the cleanup of lead contaminated wastewaters in combination with proper biomass disposal alternatives. Also, the findings can be used for performing further non‐hydroponics experiment to mimic the real wetland conditions more closely.     

Comparative Assessment of Sludge Pre‐Treatment Techniques to Enhance Sludge Dewaterability and Biogas Production

Effectiveness of ultrasonication, microwave technologies, and enzyme addition prior to anaerobic digestion is investigated using sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant to improve methane production, enhance dewaterability characteristics of the sludge, and to reduce excess sludge. Microwave pre‐treatment (1500 W, 10 min at 175 °C) results in better extra digester performance (compared to the control reactor) in terms of methane production (25 m³ ton^?1 suspended solids (SS)) than ultrasound (no improvement) and enzyme pre‐treatment (11 m³ ton^?1 SS). While methane production is not improved as a result of ultrasonication pre‐treatment (15 000 kJ kg^?1 SS), a noticeable increase (19%) is observed in the case of microwave pre‐treatment. Higher compactibility values are obtained after ultrasonication and microwave application compared to the control (i.e., from 7.1 to 8.7 and 9.2%, respectively) before anaerobic digestion. Although ultrasonication and microwave application decrease the dewaterability of the raw sludge (capillary suction time (CST) from 827 to 1364 and 2290 s, respectively), similar dewaterability results are obtained at the end of the anaerobic digestion process for all pre‐treated sludge samples. An economic assessment of this study shows that pre‐treatment with microwave results in more than 10‐fold less net cost compared to the enzyme application.     

Waste Activated Sludge Disintegration in an Ultrasonic Batch Reactor

The production of excess sludge is one of the most serious challenges in biological wastewater treatment. In the present work, disintegration is added as a new additional unit operation in a wastewater treatment plant, and the main objective is to reduce the amount of excess sludge. The use of high power ultrasound can effectively disintegrate the bacterial cells, and thereby, enhance the subsequent biodegradation during digestion. In the study, attempts are made to determine the disintegration capacity of waste activated sludge that has different total solids (TS) concentrations with low ultrasound frequency (20 kHz) and a fixed amplitude value (50%). The results show that in terms of soluble chemical oxygen demand (SCOD) release, sludge disintegration was primarily governed by ultrasonic density (W mL^–1), whereas specific energy input appears to be more critical for protein release. A SCOD release of about 329 mg SCOD gTS^–1 was obtained at a TS content of 2% and specific energy input of 5 kWs gTS^–1. The SCOD release decreased to 248.5 and 124.2 mgSCOD gTS^–1 at TS contents of 4 and 6%, respectively. The highest protein release of 80.7 mg gTS^–1 was obtained at a TS content of 2% and a specific energy input of 10 kWs g^–1. The sludge disintegration efficiency declined significantly at higher TS content.     

Behavior of Steroid Hormones and Conjugates During Wastewater Treatment – A Comparison of Three Sewage Treatment Plants

The fate of the steroid hormones 17 β‐estradiol, estrone, estriol, 16 α‐hydroxyestrone, and β‐estradiol 17‐acetate, the hormone‐conjugates β‐estradiol 3‐sulfate and estrone 3‐sulfate, and the oral contraceptives 17 α‐ethinylestradiol and mestranol were studied during wastewater treatment as wastewater treatment plants are the major source contamination of urban surface waters with steroid hormones. The elimination efficiencies of three different concepts of WWTPs, i. e., activated sludge versus trickling filter, were compared over four weeks at different weather conditions. While larger WWTPs operating on activated sludge eliminated hormones more constantly than smaller WWTPs, heavy rainfall events led to a collapse of the elimination efficiency. By using trickling filter techniques for the treatment of wastewater an elimination of the steroid hormones could not be observed. Additionally, mass flows on a per person basis are compared. In the three experiments, which ran continuously for four weeks each, it turned out that the concentrations of ethinylestradiol and mestranol were below 6 ng/L in all samples. The inflow concentrations were 70 to 82 ng/L (estrone), 17 to 44 ng/L (estradiol), 61 to 130 ng/L (hydroxyestrone), 189 to 255 ng/L (estriol), 10 to 17 ng/L (estrone‐3‐sulfate) and about 28 ng/L (estradiol‐3‐ sulfate). While in the activated sludge treatment plants the elimination of estrone was 90 and 50%, respectively, estrone was formed from precursors in the trickling filter plant. A similar situation occurred for 17β‐estradiol, estrone 3‐sulfate, and estradiol 3‐sulfate. Hydroxyestrone was eliminated with similar efficiencies in all wastewater treatment plants (64 to 82%), as well as estriol (34 to 69%). Accordingly, the emissions of the wastewater treatment plants differed largely and were not attributed to the size of the respective plant, only.     

Occurrence of Phthalates in Sewage Sludge from Three Wastewater Treatment Plants in Istanbul,Turkey

Phthalates are considered priority pollutants because of their potential adverse effects on ecosystems and human health. The objectives of this study were to determine the occurrence of five phthalates (DMP, DEP, DBP, BBP, and DEHP) in sewage sludge and to determine the seasonal variability of these contaminants at three (Bahçe?ehir, Pa?aköy, and Tuzla) full‐scale municipal and domestic wastewater treatment plants (WWTP) in Istanbul, Turkey. Mass balance was also calculated for DEHP at Tuzla WWTP sludge treatment units. DMP, DEP, DBP, BBP, and DEHP concentrations in sewage sludge ranged from 1.4 to 2.7 mg/kg dry weight (dw), 1.1 to 2.8, 0.6 to 4.6, 2.8 to 6.2, 18 to 490 mg/kg dw, respectively. Phthalate concentrations from the Bahçe?ehir and Pa?aköy WWTPs met the limit (100 mg/kg dw) of Turkey national sludge regulation and the Europe Union draft of sludge directive for land application, whereas phthalate concentrations from Tuzla WWTP exceeded the maximum permissible concentration. Phthalate concentrations did not show seasonal variations for Bahçe?ehir and Pa?aköy WWTPs, which receive mainly household wastewater while some fluctuations were observed DEP, DBP, and DEHP at Tuzla WWTP which has a lot of industrial wastewater contribution. The mass balance showed that approximately 17% of DEHP in the primary and secondary sludge was removed by anaerobic digestion, while 43% returned back to the beginning of the WWTP and 40% remained in the dewatered sludge. This study suggests that phthalates in sludge from WWTPs with industrial wastewater contribution may limit the use of sludge for land application.     

Flocculation–Sedimentation Combined with Chemical Oxidation Process

Flocculation and sedimentation of particles are essential to many environmental and industrial processes. Solid–liquid separation in olive‐oil mill wastewater treatment by means of Fenton system is the key to work continuously and maintain a constant outlet flow of clarified water at the end of the oxidation process. Natural sedimentation is not capable to eliminate the sludge formed. The efficiency of flocculation operation using different flocculants as QG‐2001, QG‐2002, DQGALFLOC‐130H, and Nalco‐77171 was investigated. The optimum dosage of each flocculant, 150, 2.5, 66, and 6 mg dm^?3, respectively, was determined. The results revealed that the best flocculant was Nalco‐77171, which determined 13.5% v/v final sludge separation and 86.5% v/v final clarified water obtained. Kinetics of sludge removal in the transition zone was adjusted to power law, v/v₀ = Kt^ε, where the exponent, ε, varied in the range 0.141–0.670.     

Grundlagen für die Dimensionierung der Belüftung bei Belebtschlammanlagen

Summary The generally accepted theory for the calculation of the oxygen consumption caused by the microbes in an aeration basin assumes that the total of oxygen utilizedq _g is the sum of the endogenous respiration of the sludgeq _e plus a quantity for substrate respirationq _s . This theory—though physiologically probably not quite correct—, is very convenient because it allows a causal calculation of the necessary oxygen input into an activated sludge plant. Extensive data on endogenous respiration of activated sludge are presented (Table 1 and 5) and are correlated with sludge load and sludge age (Fig. 4 and 5). The term substrate respiration is discussed and a calculation method, based on the removal of organic C by the mixed liquor, is proposed. In view of the fact that nitrification is an inevitable reaction in activated sludge treatment (its extent being strictly a function of the operation parameters of a plant), oxygen consumption for the oxidation of ammonia has to be included into the term of substrate respiration. The amount of this oxygen fraction has to be predicted from the degree of nitrification to be expected at the desired operation conditions. The following formula for the calculation of the oxygen input into a completely mixed aeration basin is proposed (explanations of symbols see annex): or This same calculation method may be applied stepwise for aeration basins of the tubular reactor type (longitudinal flow basins) considering the concentration decrease of the substrates along the length profile of the basin (the term for endogenous respiration can be assumed constant for the entire aeration time).

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Evaluation of Sludge Digester Effluent as Feeding Solution for the Enrichment of Anammox Bacteria

The aim of this study is to evaluate the feasibility of sludge digester effluent as feeding solution to enrich anaerobic ammonium oxidation (anammox) bacteria. The performance of the two parallel pilot scale‐upflow packed bed anammox reactors (UPBAn1 and UPBAn2) are examined in terms of the enrichment of anammox bacteria. The control experiment is set up conducting synthetic wastewater as feeding solution in the UPBAn1 reactor whereas, the sludge digester effluent is fed to the nitritation reactor and then the partially nitrated digester effluent to the UPBAn2 reactor. Anammox activities are evaluated by mass balances based on ammonium (NH₄⁺), nitrite (NO₂^?), and nitrate (NO₃^?) analysis and NRR. Microbial community of anammox bacteria is analyzed using real‐time polymerase chain reaction (PCR). The results demonstrate that UPBAn 1 and UPBAn2 reactors are successfully enriched on days 64 and 40 with NRRs of 19.54 and 19.43 g N m^?3 per day, respectively. This study reveals that both synthetic wastewater and digester effluent are suitable for the enrichment of anammox bacteria; however, digester effluent as feeding solution for enrichment of anammox bacteria based on the ease of process control and process stability is more advisable.     

Treatment of Synthetic Olefin Plant Wastewater at Various Salt Concentrations in a Membrane Bioreactor

The objective of this study was to investigate the effect of salt concentration on performance of a membrane bioreactor (MBR) for treating an olefin plant wastewater. For this purpose, a lab‐scale submerged MBR with a flat‐sheet ultrafiltration membrane was used for treatment of synthetic wastewater according to oxidation and neutralization unit of olefin plant. The synthetic wastewater was adjusted to have 500 mg/L chemical oxygen demand (COD). Trials on different concentrations of sodium sulfate (Na₂SO₄) (0–20 000 ppm) in the feed were conducted under aerobic conditions in the MBR. The results showed that increasing the salt concentrations causes an increase in the effluent COD, phenol, and oil concentrations. These results are due to reduction of the membrane filtration efficiency and also decline in the microbial activity that it is indicated by decreasing the sOUR in MBR. But in all the trials, the effluent COD and oil concentration was well within the local discharge limit of 100 and 10 mg/L, respectively. These results indicate that the MBR system is highly efficient for treating the olefin plant wastewater, and although high salt concentrations decreased organic contaminant removal rates in the MBR, the effluent still met the discharge limits for treating the olefin plant wastewater.     

Role of a moderately halophilic bacterial consortium in the biodegradation of polyaromatic hydrocarbons

Polycyclic aromatic hydrocarbons are ubiquitous pollutants in the environment, and most high molecular weight PAHs cause mutagenic, teratogenic and potentially carcinogenic effects. While several strains have been identified that degrade PAHs, the present study is focused on the degradation of PAHs in a marine environment by a moderately halophilic bacterial consortium. The bacterial consortium was isolated from a mixture of marine water samples collected from seven different sites in Chennai, India. The low molecular weight (LMW) PAHs phenanthrene and fluorine, and the high molecular weight (HMW) PAHs pyrene and benzo(e)pyrene were selected for the degradation study. The consortium metabolized both LMW and HMW PAHs. The consortium was also able to degrade PAHs present in crude oil-contaminated saline wastewater. The bacterial consortium was able to degrade 80% of HMW PAHs and 100% of LMW PAHs in the saline wastewater. The strains present in the consortium were identified as Ochrobactrum sp., Enterobacter cloacae and Stenotrophomonas maltophilia. This study reveals that these bacteria have the potential to degrade different PAHs in saline wastewater.     

Vorkommen und Bewertung polyzyklischer aromatischer Kohlenwasserstoffe in einem mit kommunalen und industriellen Abwässern belasteten Fließgewässer

The river with a catchment of 5,400 km² is investigated over a length of 230 km at seven stations for the total concentration of six polycyclic aromatic hydrocarbons (PAH) and the total of three carcinogenic polycyclic substances (CPS) in the water by means of thin-layer chromatography. The maximum load occurs in the lower course downstream of large industrial wastewater introduction points with 5.1 μg/l polycyclic aromatic hydrocarbons, whereas in the upper course the maxima are at 2 … 3 μg/l polycyclic aromatic hydrocarbons for a mainly municipal pollution. The average daily load increases from 0.146 kg/d PAH and 0.048 kg/d CPS to 4.168 and 1.401 kg/d, respectively. In the flowing water there cannot be observed any self-purification concerning these substances, by an interconnected storage reservoir seston is reduced and thus also the PAC-concentrations are reduced by 50 … 60%. The PAH-concentration shows a significant positive correlation with the COD-Mn and the ammonium concentration. There is also a good agreement between the concentrations measured and the concentrations calculated from the wastewater load in the longitudinal section of the river.     

Using Na/K Ratios to Identify the Potential Impacts of Sewage Effluent on Groundwater Quality in Sohag,Egypt

Improper disposal of wastewater is an important source of groundwater contamination, as it poses serious threats to the environment and human health. In this case study, 18 groundwater and 3 sewage effluent samples were collected from the area adjacent to a wastewater treatment plant in Sohag, Egypt. These samples were subjected to detailed chemical and bacteriological analyses to quantify the potential impact of sewage effluent on the groundwater quality using geochemical indicators. The groundwater aquifer in the study area is represented by the highly permeable Qena Sands that are composed of sands and gravels. The bacteriological analyses indicated the presence of fecal coliform in groundwater at wells nearby the wastewater ponds and farm lands. NH₄ concentration of the contaminated groundwater samples ranged from 0.36 to 5.70 mg/L (78% of the samples > 1.20 mg/L) and the NH₄ in the non‐impacted samples ranged from 0.40 to 2.23 mg/L (22% > 1.20 mg/L). Variations in NH₄ concentrations are due to the transformation processes occurring in the aquifer. The groundwater samples were categorized based on the Na/K ratio into two classes. The first class shows the Na/K ratios vary from 2.52 to 12.19 for sewage effluent and contaminated samples, while in the second class they range from 12.85 to 31.60 for non‐impacted samples. As a result, the Na/K ratio in combination with other chemical and microbiological indicators is a useful screening tool for assessing possible sewage influence on shallow groundwater from shallow wells.     

Optimierung des Belebungsverfahrens durch Minimierung des Volumens von Belebungs- und Nachklärbecken

The separate examination of the processes of the settling and thickening of activated sludge allows us to minimize the volumes of aeration tanks and final clarification tanks. The following initial quantities are given: wastewater quantity, inflow and outflow concentrations of BOD₅, wastewater temperature and reflux ratio of activated sludge and, in addition, three parameters of the thickening behaviour of activated sludge as well as a parameter for the bioactivity of sludge, which are to be determined in an experimental plant. From this, the optimum concentration of the activated sludge in the aeration tank is calculated at which the total of volumes for aeration tank and final clarification tank becomes a minimum. The process is carried out numerically by an example.     

Simultaneous Organic Matter and Nitrogen Removal from Piggery Slaughterhouse Wastewater Using Bioaugmented Gaslift Membrane Bioreactor

A single bioaugmentation reactor and a side-stream gaslift membrane bioreactor combined with bioaugmentation are conducted to treat real wastewater from a centralized piggery slaughterhouse in Vietnam. The bioaugmented reactor is inoculated with heterotrophic microorganisms (Bacillus sp.) isolated from piggery slaughterhouse wastewater. The results of a single bioaugmentation experiment show high removal efficiency of chemical oxygen demand (COD) (84.8%–97.5%) and total nitrogen (TN) (69.9%–87.2%) at loading rates of 1.28–3.89 and 0.14–0.37 kg m⁻³ d⁻¹, respectively. The combined system demonstrates a significantly higher TN removal efficiency (89.0%–96.1%) (p < 0.001), more stable flux (36.0–38.4 L m⁻² h⁻¹), and transmembrane pressure (0.95–1.05 bar), and better capacity of separation of solid–liquid phases compared to the single bioaugmentation. High COD and TN removal efficiency is possibly due to assimilation and simultaneous nitrification and denitrification processes. The results of this study also indicate the feasibility and propitious efficiency of the bioaugmented gaslift membrane bioreactor for piggery slaughterhouse wastewater treatment.     

Investigation on the Levels of Heavy Metals,Polycyclic Aromatic Hydrocarbons,and Polychlorinated Biphenyls in Sewage Sludge Samples and Ecotoxicological Testing

This article reports the levels of heavy metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in sewage sludges taken from two wastewater treatment plants (WWTPs) in Konya (Turkey) as well as their toxicity. The concentrations of heavy metals, including Cd, Cr, Cu, Ni, Pb, Zn in sludge samples from plant #2 did not exceed the limits described in both Turkish and European Union (EU) regulations. The similar result was observed in samples obtained from plant #1, except for sludge taken in May 2010. The ΣPAHs concentration ranging from 960 to 7680 µg/kg dry matter shows that sewage sludges from plant #1 could be used for agricultural purpose. However, sewage sludges from plant #2 (ΣPAHs: 1077–17 509 µg/kg dry matter) was not suitable for using in agriculture. The concentrations of ΣPCBs in all investigated sludges from plant #1 (7.46–709.36 µg/kg dry matter) and plant #2 (14.12–788.47 µg/kg dry matter) were lower than the limits reported in Turkish and EU regulations. The probable sources of PAHs and PCBs in sludges were also determined. The ecotoxicological tests examined on Vibrio fischeri and Lepidium sativum organisms showed that sludges from plant #1 had no significant toxic effect, while sludges from plant #2 had acute toxic property. Finally, all the results showed that sewage sludges from plant #1 had potential for being used in agriculture.