Municipal Sewage Plant Research Articles

PHYSICOCHEMICAL CHANGES IN MUNICIPAL WASTEWATER TREATMENT PLANT

The physicochemical parameters comprise pH, temperature (T), chemical oxygen demand (COD), alkalinity, and ammonia NH3, . The results obtained in this study were as follows: temperature (21.6 -23.7ºC), pH (7.69 - 7.51), ammonia NH3 is in range 0 to 1.8 mg/L and Chemical oxygen demand (COD) is in range ( 13 – 620mg/L), and alkalinity (370-200 mg/L). . We conclude that these municipal sewage plants are important point sources of pollution in surface water with possible public health and ecological risks. The present paper comprises of the various Physico-Chemical parameters and technologies used in waste-water treatment, with emphasis on municipal waste-water.

Environmental Impact Analysis and Carbon Emission Reduction Pathways by Upgrading Wastewater Treatment Plant: A Case Study of Upgrading Project at a Wastewater Treatment Plant in Dongguan, China

The potential environmental impact and increased operational costs associated with the upgrading and renovation of sewage treatment plants are acknowledged. This study employs the upgrading and expansion project of a municipal sewage plant in Dongguan City, Guangdong Province, as a case study. Utilizing the principles and methods of the Life Cycle Assessment (LCA), a comprehensive assessment of the environmental benefits during the upgrading and renovation process of the sewage treatment plant, is conducted and targeted solutions are proposed. The research findings indicate that upgrading and renovating sewage treatment plants can significantly augment the adverse environmental effects of such facilities. Therefore, this study strategically proposes measures such as the utilization of clean energy, sludge resource utilization, and recycled water use as carbon emission reduction pathways. Through calculations, it is demonstrated that the utilization of clean energy and sludge resource can respectively reduce electricity consumption by 12.41% and 59.06%. Concurrently, recycled water use can lead to a reduction of 68.65% in carbon emissions, thereby markedly enhancing positive environmental outcomes.

Effect of Potassium Ferrate as a Dewatering Conditioner on Sludge Pyrolysis Characteristics and the Releasing Characteristics of Nitrogen, Sulfur, and Chlorine during Sewage Sludge Pyrolysis

Sludge pyrolysis is a promising method for treating excess sludge as a by-product of municipal sewage plants, allowing for energy self-sufficiency and resource recovery. Before sludge pyrolysis begins, a few conditioning agents are added to the sludge that promote sludge dewatering. Potassium ferrate (K2FeO4) is applied as a conditioning agent with both cracking and flocculation effects, but the effects of K2FeO4 on the release characteristics of nitrogen, sulfur, and chlorine during sludge pyrolysis have not been elucidated. In this study, we analyzed the sludge pyrolysis characteristics and chemical state changes of N, S, and Cl contaminants in the dewatered sludge after K2FeO4 conditioning before and after pyrolysis. Further, the release characteristics of condensable/noncondensable gases during pyrolysis were assessed using thermogravimetric mass spectrometry (TG-MS) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) analyses before and after conditioning. We found that potassium pertechnetate reduced the activation energy required for the sludge in the pyrolysis process. Noticeably this process made the sludge more susceptible to thermal decomposition leading to volatile production and also influenced the release of different contaminants generated by the pyrolysis process. Moreover, K2FeO4 promoted the release of C/H/O gases and reduced the release of N/S/Cl pollutant gases from the sludge. Overall, this study provides a theoretical basis for the selection of conditioning agents for the sludge conditioning and dewatering steps during the sludge pyrolysis process.

Systematic Evaluation of Low-carbon Operation of Typical A2O Processes in Municipal Sewage Plant

Under the "Carbon Peak, Carbon Neutral" goal, the systematic evaluation of the carbon emission equivalent (CO2eq) and its compositions of the typical A2O process has important guiding significance for the low-carbon operation of most municipal sewage plants in China. Based on the operational data on the first municipal sewage plant of Jiaozuo in 2020 and the methods presented in "2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, " a systematic evaluation of the CO2eq of the typical A2O process was established, including direct emissions that were built on the Arrhenius model introducing the water temperature factor and indirect emissions from the three aspects of electricity consumption, agent addition, and sludge transportation. The results showed that the daily emission intensities of CH4 and N2O were (115±56) kg·d-1 and (30±18) kg·d-1, respectively. Additionally, indirect carbon emissions from electricity consumption and agent addition accounted for 48.4% and 51.3% in the biochemical treatment section, respectively. In 2020, CO2eq amounts of total research plant and per unit sewage were 2.17×104 t and (0.63±0.07) kg·m-3, respectively. The magnitude of the proportion of different carbon emission compositions was as follows:sewage electricity (36.5%)>sewage agent (26.6%)>N2O direct (15.4%)>sludge agent (9.6%)>sludge electricity (6.7%)>CH4 direct (4.9%)>sludge transportation (0.3%). System import/export fluxes of carbon and nitrogen elements were calculated, followed by the carbon to nitrogen mass ratio in the sewage plant. Direct carbon emission characteristics of CH4 and N2O and their influencing factors were discussed, respectively. Based on the balance theory of carbon and nitrogen elements in the system, it is proposed that the selective introduction of industrial wastewater may become an important reference measure for the low-carbon operation of municipal sewage plants in the future.

Modeling and optimizing of an actual municipal sewage plant: A comparison of diverse multi-objective optimization methods

The activated sludge process of an actual municipal sewage treatment plant was systematically modeled, calibrated, and verified in this study. Identified multi-objective optimization (MOO) methods were employed to optimize the process parameters of the validated model, and the optimal MOO algorithm was obtained by comparing Pareto solution sets. The optimization model consisted of three key evaluation indicators (objective functions), which are the average effluent quality (AEQ), overall cost index (OCI), and total volume (TV) of the biochemical tank, along with 12 more process parameters (decision variables). Three optimization algorithms, i.e., adaptive non-dominated sorting genetic algorithm III (ANSGA-III), non-dominated sorting genetic algorithm II (NSGA-II), and particle swarm algorithm (PSO), were adopted using MATLAB. The comparison of these algorithms demonstrated that the ANSGA-III algorithm had better Pareto solution sets under the triple objective optimization, and the effluent quality of COD, TN, NH4+-N, and TP after optimization decreased by 2.22, 0.47, 0.13, and 0.02 mg/L, respectively. Additionally, the simulated AEQ was reduced by 13% compared to the original effluent, and the OCI and TV decreased from 21,023 kWh d−1 and 17,065 m3 to 20,226 kWh d−1 and 16,530 m3, respectively. The reported ANSGA-III algorithm and the proposed multi-objective method have a promising ability for energy conservation, emission reduction, and upgrading of municipal sewage treatment plants.

Pollution Characteristics and Risk Assessment of DBPs in Typical Drinking Water Sources in Wuhan Under the COVID-19 Pandemic

In order to reveal the pollution characteristics and risk levels of DBPs in typical drinking water sources in Wuhan under the COVID-19 pandemic, 26 sampling sites were selected in typical drinking water sources in Wuhan. N,N-diethyl-1,4-phenylenediamine spectrophotometry and gas chromatograph-micro-cell electron capture detector (GC-μECD) methods were used to detect residual chlorine disinfectants and DBPs in water, respectively, and their health and ecology risks were assessed. The results showed that free chlorine or total residual chlorine were detected in 16 of the 26 water samples, and the maximum concentration was 0.04 mg·L-1, which exceeded the limit of the surface water standard in China. The concentration of residual chlorine was higher in sampling sites near the outfall of a municipal sewage plant. There were 34 types of DBPs measured in 10 sampling sites, and 24 types of substances were detected with the detection rate of 10.00%-100.00%. The ρ (total DBPs) was in the range of 0.11-104.73 μg·L-1, with an average value of 7.26 μg·L-1. The concentration of chloroform was the highest among all the DBPs, ranging from 9.98 μg·L-1 to 11.15 μg·L-1, with an average value of 10.47 μg·L-1. The concentration of 2-bromo-2-iodoacetamide was the lowest, ranging from ND-0.11 μg·L-1, with an average value of 0.01 μg·L-1. The overall detection level of the DBPs area was low in this study area, and the result of the health risk assessment showed that the DBPs had no carcinogenic or non-carcinogenic health risks to human body. However, the results of the ecological risk assessment showed that chloroform presented a high ecological risk to aquatic organisms.

Antifouling membranes employing a 2D planar nanobiocatalyst of crosslinked glucose oxidase aggregates wrapping extra-large graphene oxide

This paper presents highly effective antimicrobial surfaces employing a 2D structured nanobiocatalyst composed of graphene oxide (GO) and glucose oxidase (GOD). Enzyme molecules are immobilized onto extra-large GO pieces with a plane dimension of approximately 100 μm via an enzyme adsorption, precipitation, and crosslinking (EAPC) approach. This enables the effective wrapping of extra-large GO pieces by a matrix of crosslinked enzyme aggregates, which improves the enzyme loading. Consequently, the measured GOD activities of the EAPC sample via 50% (w/v) ammonium sulfate precipitation are 4,940 and 3,820 times higher than those of the control samples, i.e, the enzyme adsorption (EA) and enzyme adsorption/crosslinking (EAC) samples, respectively. The preservation of the planar GO geometry with an extra-large surface also allows the effective binding of EAPC onto a commercial membrane filter via a polydopamine coating, thus yielding a biocatalytic EAPC membrane. Compared to the commercial membrane with no bound EAPC, the in situ generation of H2O2via the EAPC-catalyzed oxidation of glucose on the membrane surface demonstrated enhanced filterability against a mixed bacterial population of activated sludge obtained from a municipal sewage plant as well as two model bacteria: gram-negative Pseudomonas aeruginosa and gram-positive Staphylococcus aureus. The bacterial decontamination of the EAPC-bound membrane surface can also be activated on demand by simply adding glucose to the bulk solution. This newly proposed mechanism of antifouling surfaces employing a localized nanobiocatalytic conversion of nontoxic glucose to bactericidal H2O2 can provide insights for biofouling control via a highly effective and environment-friendly approach.

Adsorptive removal of plasticizer (dimethyl phthalate) and antibiotic (sulfamethazine) from municipal wastewater by magnetic carbon nanotubes

In this study, the adsorptive removal of plasticizer (dimethyl phthalate, DMP) and antibiotic (sulfamethazine, SMT) from synthetic and municipal wastewater was studied using multi-wall carbon nanotubes (MWCNTs) and magnetic (Fe3O4) MWCNTs. The competition of SMT and DMP for the adsorptive sites was examined. The adsorption kinetics, isotherms, thermodynamics, as well as the effect of initial pH and competitive adsorption of DMP and SMT were determined. Results showed that both adsorption processes were endothermic, and the maximum adsorption capacity for DMP was calculated to be 196.85 mg g−1 (MWCNTs) and 136.99 mg g−1 (Fe3O4/MWCNTs) at 303 K according to the Langmuir model. The second-order kinetic model and the Freundlich isotherm model could fit the experimental data. In addition, there was a competitive relationship between SMT and DMP for the adsorptive sites of Fe3O4/MWCNTs and MWCNTs, and DMP had obvious competitive effect on the SMT adsorption by Fe3O4/MWCNTs, possibly due to the electrostatic interaction. The adsorption capacity for SMT or DMP decreased in the influent and effluent of municipal sewage plant than that in the deionized water and tap water. Both adsorbents were effective in removal of COD/TOC and targeted pollutants.

Biodegradation of lincomycin in wastewater by two-level bio-treatment using chloroperoxidase and activated sludge: Degradation route and eco-toxicity evaluation

Abstract Lincomycin, which has been found in wastewater treatment plants and groundwater, could cause potential environmental problems due to their adverse effects on people and aquatic environments. At present, conventional physical or chemical methods cannot efficiently remove this drug from effluent. In this study, a rapid and effective method of enzymatic degradation of lincomycin with the use of chloroperoxidase (CPO) is proposed. By using 1.5 × 10−8 mol ⋅ L−1 CPO, a lincomycin degradation efficiency of 90.16 % was achieved in 20 min at pH 3.0. The degraded products were detected by HPLC-MS, which indicated that lincomycin was decomposed into two fragments. The eco-toxicity evaluation by 72 h EC 50 determination with the use of Chlorella pyrenoidosa as indicator showed that the degraded lincomycin was less toxic than the original lincomycin molecule. Moreover, it was found that when this method of enzymatic degradation by CPO was followed by activated sludge treatment, the COD removal of lincomycin effluent could be significantly enhanced. Thus, the proposed two-level bio-treatment of lincomycin may have potential application in municipal sewage plant s for the complete removal of this drug. The immobilization of CPO on a dendritic mesoporous silica particle improved its application effectively.

Potential of Lemnoideae Species for Phytoremediation of Fresh Water with Elevated Manganese Concentration

Background . Wastewater treatment using physical, chemical, and biological methods is primary solution for the reduction of water pollution that reaching the critical thresholds. The members of subfamily Lemnoideae , commonly called duckweed, are considered the most efficient aquatic plants for wastewater remediation. Although properties of duckweed to survive in water with high concentration of heavy metal ions such as chromium, cobalt, lead, nickel and cuprum are well documented, the growth of duckweed in water with high concentrations of manganese and the efficiency of retention of manganese from water by these species has not been estimated. Objective . Four duckweed species ( Spirodela polyrhiza , Landoltia punctata , Lemna aequinoctialis , and L. turionifera ) were used for establishment of influence Mn on their vitality and growth and for studying their potential for phytoremediation of fresh water with elevated manganese concentration. Methods . Duckweed collected in Eastern China was introduced in tissue culture in vitro by surface sterilization. The identification of the collected duckweed species was determined by DNA barcoding using primers specific for chloroplast intergenic spacers atpF - atpH (ATP) and psbK - psbL (PSB). The experiments for establishment of influence Mn on duckweed growth carried out in aseptic condition. To determinate concentration of Mn, the samples of different water type (Hongze Lake, ponds around Hongze Lake, Huaian local municipal sewage plant and industrial sewage plant) were analyzed by the Inductively Coupled Plasma Optical Emission Spectrometry. Results . The most sensitive duckweed to Mn was S. polyzhiza , the first characteristic symptoms of toxicity like brown spots have appeared when concentration of Mn was 40 mg/L, the concentration 200 mg/L Mn resulted in chlorosis and death of fronds. L . aequinoctialis and L. turionifera had similar effects in SH medium supplemented with 650 mg/L and 975 mg/L Mn, respectively. L . punctata was the most tolerant duckweed to Mn plants continued to grow even at concentration 975 mg/L. Response of duckweed on Mn was dependent on availability of nitrogen in nutrient medium. Using four duckweed species for treatment of water containing 4.12 mg/L Mn allowed to reduce concentration until safe level of standard (0.1 mg/L Mn). Conclusions . All investigated duckweed species ( S. polyrhiza, L. punctata , L. aequinoctialis , and L. turionifera ) were characterized by a high level of resistance to manganese, especially L. punctata. Response of duckweed on Mn was dependent on availability of nitrogen in nutrient medium. The tested species of subfamily Lemnoideae were high effective for phytoremediation of water with elevated manganese concentration.

Performance of constructed wetlands with different substrates for the treated effluent from municipal sewage plants

Abstract Constructed wetlands (CWs) are effective as an advanced treatment process for the treated effluent of municipal wastewater plants. An appropriate substrate, suitable macrophytes, and proper operation are crucial for pollutant abatement. In this research, three subsurface flow CWs with various substrates were investigated. Pollutants abatement efficiency under various operational schemes were analyzed. The results showed that the satisfactory hydraulic loading rate was 0.25 m3/(m2·d). When the C/N ratio of influent was adjusted to 5.87 by adding a carbon source, the denitrification and dephosphorization efficiency would be improved, with 7–8 mg/L for total nitrogen (TN) and 0.4 mg/L for total phosphorus (TP) in the effluent, which can achieve the Class 1A Discharge Standard for discharge to natural waterways in China. A greater depth of submersion for the substrate layer resulted in a more conducive environment for the abatement of nitrogen substances. However, a 40-cm depth of submersion in CWs results in better removal efficiency of TN and TP. A plastic ring substrate (PRS) contains biological enzyme promoter formula, which was conducive to nitrifying and denitrifying bacteria. The biofilm affinity and coordination with plants made the PRS more effective than the other two substrates, especially for NO3–-N and TN abatement efficiency.

Rapid and efficient enzymatic degradation of metsulfuron-methyl and its removal by bio-cascade treatment

Metsulfuron methyl is typical sulfonylurea herbicides. The degradation of metsulfuron-methyl has aroused research interests because it was mobile in natural media, and raising environmental concerns about contamination of metsulfuron-methyl to surface water. However, conventional methods cannot remove these herbicides from water efficiently. This work proposed a rapid and efficient enzymatic degradation of metsulfuron-methyl by chloroperoxidase (CPO). The effect of reaction conditions, including pH, concentration of oxidant and enzyme, and degradation time on the degradation efficiency (η) were studied and accordingly optimized. The optimum η of 93.2% for 16.7 μmol·L−1 metsulfuron-methyl was achieved after 10 min at 25 °C and weakly acidic pH. The required CPO is only 0.06 μmol·L−1. The degraded products of metsulfuron-methyl were identified by HPLC-MS. The results indicated that metsulfuron-methyl molecule was decomposed, and five smaller molecular fragments were detected. Moreover, it was found that if this enzymatic degradation was combined with following activated sludge treatment, then, this bio-cascade treatment was more effective in removal of metsulfuron-methyl in wastewater than by activated sludge alone (which was used in most municipal sewage plant). The COD removal increased from 12.09% to 74.27%. Ecotoxicity tests of 72 h EC50 for degraded solution using a green alga, Chlorella pyrenoidosa, as eco-indicator demonstrated the enzymatic degraded products had lower eco-toxicity than metsulfuron-methyl itself. Application of this bio-cascade treatment to real water sample and artificial wastewater containing metsulfuron-methyl was effectively.

Preparation of low-cost sludge-based mesoporous carbon and its adsorption of tetracycline antibiotics.

Preparation of sludge-derived mesoporous carbon materials (SMCs) through pyrolysis of excess activated sludge from urban municipal sewage plants is an effective means of reducing pollution and utilizing a waste resource. This paper presented a method of SMC preparation in which calcium oxide (CaO), polyacrylamide (PAM), and chitosan (CAS) flocculating agents were used as pore-forming additives. Physical and chemical characterizations of the prepared SMCs were conducted by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The prepared SMCs were used to adsorb a tetracycline (TC) antibiotic pollutant. The influences of pH, adsorption time, temperature, and pollutant concentration on TC adsorption capacity were determined. The experiments demonstrated that weakly acidic conditions were conducive to TC adsorption, which mainly occurs via electrostatic and π-π interactions. The TC adsorption process by SMCs conformed better to the pseudo-second-order models, indicating that chemical adsorption was the dominant adsorption process. The isothermal adsorption of TC by the SMCs conformed to the Freundlich model. This implied that TC easily adhered onto the SMC surfaces via multilayer homogeneous adsorption. Thermodynamic studies revealed that the adsorption of TC onto SMCs was spontaneous and endothermic.

Antibiotic resistance gene profiles at various treatment stages of a full-scale municipal sewage plant

Antibiotic resistance gene profiles at various treatment stages of a full-scale municipal sewage plant

Sewage Management Changes in the North-eastern Poland After Accession to the European Union

Poland's accession to the European Union contributed to the infrastructure development of the whole country. One of the elements of the modernized infrastructure is the sewage network and facilities on this network, as well as facilities for waste water treatment and disposal of sludge. A wide stream of funds flowing to the country, and consequently also to the north-eastern polish voivodeships (Podlaskie, Warmian-Masurian, Lublin), allowed modernization, organize, and sometimes to build a new sewage management of this part of the country. The main factors and parameters that allow us to evaluate the development of the sewage management in north-eastern Poland are included: percentage of population using sewage treatment plants, number of municipal sewage plants with the division of their type, number of industrial plants, number of septic tanks, amount of sewage purified in a year, amount of sludge produced in the year, design capacity of sewage treatment plant, size of plant in population equivalent (PE). From a number of investments in the field of wastewater management carried out in the discussed area in the period after Poland's accession to the European Union, 9 investments were considered the most important, 3 from each of the voivodeships.

Integration of Upscaled Microbial Fuel Cells in Real Municipal Sewage Plants

Microbial fuel cells (MFC) are a promising technology to enhance the power-efficiency of municipal sewage plants. Therefore, the possibilities of MFC implementation on municipal sewage treatment plants are analyzed in this contribution. A newly developed up-scaled cell design is described, each with an active area of 6,200 square centimeters respectively. The cell design integrates a double-sided graphite/polymer composite anode between two oxygen reducing cathodes, to enlarge the active surface area. Furthermore, the new design integrates in-situ electrode potential measurement by a reference electrode and biofilm flushing by nitrogen purge. To reach a uniform anolyte overflow, novel anodic flow patterns are described, evaluated by computational fluid dynamics. In addition to the technical cell design, the first prototype is presented. All cell elements are manufactured in an economical serial production, as well as high performance catalytic active cathodes, which are produced in-house by a semi-automatic production line.

Evaluation of potential E. coli transport from on-site sewage facilities in a Texas watershed

Potential E. coli contamination in surface waters from on-site sewage facilities was investigated in the Dickinson Bayou watershed, Texas. This watershed is listed as impaired due to bacteria by the Texas Commission on Environmental Quality. Two water quality monitoring stations, with flow meters and automatic water samplers, were installed in the watershed to assess E. coli concentrations in surface runoff. One monitoring station was installed in a neighborhood that solely used an on-site sewage facility (OSSF) and the second monitoring station, the control site, was installed in a neighborhood connected to a municipal sewage plant. For 16 runoff events at the OSSF site, the combined geometric mean E. coli concentration was 639 colony forming units (CFU)/100milliters while the geometric mean E. coli concentration for 13 runoff events at the control site was 371 CFU/100milliliters. The E. coli concentrations from the 2 sites were not statistically different, suggesting that OSSFs may not be the major cause of bacterial contamination in the Dickinson Bayou watershed. In addition, a bacterial source tracking method was employed, which concluded that a portion of the E. coli from both sites were of human origin. Citation: Morrison D, Karthikeyan R, Munster C, Jacob J, Gentry T. 2017. Evaluation of potential E. coli transport from on-site sewage facilities in a Texas watershed. Texas Water Journal. 8(1):18-28. Available from: https://doi.org/10.21423/twj.v8i1.7041.

Integration of Upscaled Microbial Fuel Cells in Real Municipal Sewage Plants

In search for appropriate processes to enhance the efficiency of municipal sewage plants, microbial fuel cells (MFC) have moved into research focus. Due to the MFC characteristic, which is able to treat wastewater while generating power simultaneously, it is also a promising approach to change the energy balance of sewage plants – switching from the biggest municipal energy consumer to an energy producer. Owing to the small power density of MFCs in comparison to chemical fuel cells, large active surface areas and therefore low-cost cell constructions, electrodes and catalysts are necessary. Challenges in MFC upscaling have been overcome and a functional and less price intensive cell design for integration in existing aeration tanks of municipal wastewater treatment plants has been developed (figure left). The new cell design integrates a double-sided graphite/polymer composite anode between two cathodes, to enlarge the surface area. It allows online half-cell potential measurement and biofilm flushing by nitrogen (figure right), among other options. High performance catalytic active cathodes are used, which are produced in-house by a semi-automatic production line. A fuel cell stack of up to fifty MFCs, each with an active area of 6000 square centimeters respectively, has successfully started operation with real municipal wastewater at the wastewater treatment plant in Goslar, Germany. In addition to the technical cell design, the wastewater parameters strongly affect the electrochemical performance of microbial fuel cells. Therefore the influences of process parameters (temperature, pH, O2, TOC etc.) were measured to determine optimized operating points when fed by real wastewater. Additionally cathodic catalysts influence the MFC performance considerably, so the electrode-performance of the scaled up microbial fuel cells were investigated by half-cell measurements. Figure 1

Chemoautotrophic denitrification based on ferrous iron oxidation: Reactor performance and sludge characteristics

Aiming at treatment of wastewaters with low C/N ratio, a novel ferrous iron-based chemoautotrophic denitrification (Fe-CAD) reactor was developed with inoculum sludge from a municipal sewage plant in Hangzhou, China. The efficiency of the Fe-CAD reactor was remarkable. The volumetric loading rate (VLR) and volumetric removal rate (VRR) of NO3− were 0.26±0.01kg-N/(m3·d) and 0.09±0.03kg-N/(m3·d), while the VLR and VRR of Fe2+ were 3.10±0.24kg-Fe/(m3·d) and 1.69±0.26kg-Fe/(m3·d), respectively. By means of next generation sequencing, the Fe-CAD sludge was found to be rich in ferrous iron-oxidizing nitrate-reducing bacteria including Rhodanobacter, Mizugakiibacter, Sulfuricella, Comamonas and Gallionella. Reaction dynamics of the Fe-CAD sludge were determined by batch experiments. After fitted by Haldane Model, the maximum specific activity (μmax), the saturation concentration (Ki) and the half inhibition concentration (Ks) of NO3− to the Fe-CAD sludge were calculated as 0.24mg-N/(h·gVSS), 72.82mg-N/L and 2722.97mg-N/L, while the μmax, Ki, Ks of Fe2+ were 2.28mg-Fe/(h·gVSS), 203.09mg-Fe/L and 229159.38mg-Fe/L, respectively. The produced ferric iron formed an brilliant yellow iron-encrustation with irregular shape around the functional microorganisms, and the iron-encrustation resulted in a dropped specific activity of the Fe-CAD sludge. Removal or prevention of the iron-encrustation around microbial cells were suggested to be the key to improve the performance of the Fe-CAD reactor.

Content of PAHs, activities of γ-radionuclides and ecotoxicological assessment in biochars

Abstract The aim of this research was to determine the effect of thermal conversion temperature and plant material addition to sewage sludge on the PAHs content and the activity of selected γ-radionuclides in biochars, and to conduct an ecotoxicological assessment. The pyrolysis of the mixtures of sewage sludge and plant materials at 300°C and such temperature caused an increase in the contents of 2- and 3-ring hydrocarbons. During the pyrolysis of organic materials at 600°C, the amount of the following compounds was reduced in biochars: benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3c,d]pyrene, dibenzo[a,h]anthracene, and benzo[g,h,i]perylene. Among γ-radioisotopes of the elements, natural radiogenic isotopes were dominant. 137Cs was the only artificial radioactive isotope. The pyrolysis of the mixtures of municipal sewage sludge and plant materials revealed that isotope 40K had the highest radioactive activity. In the case of other analysed nuclides, activities of 212Pb, 214Pb, 214Bi, and 137Cs were determined after the sample pyrolysis. The extracts from the mixtures of sewage sludge and plant materials were non-toxic to Vibrio fischeri.