Wastewater treatment plants (WWTPs) are known sources of contaminants of emerging concern (CECs) spreading into the environment, as well as, of unpleasant odors. CECs represent a potential hazard for ...human health and the environment being pharmaceutical or biologically active compounds and they are acquiring relevance in European directives. Similarly, the public concern about odour emissions from WWTPs is also increasing due to the decreasing distance between WWTP and residential areas. This study focuses on the effectiveness of the recently developed MULESL technology (MUch LEss SLudge; WO2019097463) in removing CECs and limiting odour emissions from WWTPs. MULESL technology has been developed for its ability to reduce up to 80% the sludge production from WWTPs. However, it is ought to evaluate if the benefits coming from sludge production reduction do not invalidate CECs removal or negatively affect odour emissions. Thus, the performances of a MULESL and a conventional WWTP (flow rate of 375 m3/d and 3600 m3/d, respectively) were compared while treating the same municipal sewage.
Whereas both plants succeeded in removing the traditional gross parameters characterizing wastewaters (e.g. chemical oxygen demand, nitrogen), the MULESL was much more effective than the conventional one in terms of CECs removal for about 60% of the identified compounds showing, however, the same or lower effectiveness for about 30% and 10% of them, respectively. This result was attributed to the high sludge retention time and biomass concentration in the MULESL (enabling enrichment of slow growing microorganisms and forcing biomass to use unusual substrates, respectively), and to the biomass feature to grow in the form of biofilm and granules (favoring micropollutants absorption on biomass).
Furthermore, odour impact analysis has shown that the MULESL was characterized by a much lower impact, i.e. 45% lower than that of primary and secondary treatments of the conventional WWTP.
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•An innovative wastewater treatment plant design, referred to as MULESL, is presented.•The MULESL showed higher stability in nitrogen removal than conventional plant.•The MULESL removed several emerging pollutants refractory to conventional treatments.•Odour emissions from the MULESL were 45% lower than from the conventional plant.
Sewage sludge reuse in agriculture is increasing, however it can be an important route for contaminants to enter the environment. The aim of this study was to evaluate earthworm Eisenia fetida ...capability to reduce heavy metal content in the sewage sludge (SS) amended soil and increase soil fertility in terms of soil nutrients content. Adult earthworms were introduced into aged SS amended soil (0–200 Mg ha-1) and left for 65 days. Earthworms have stabilized soil pH and accelerated organic matter mineralization. The concentrations of most heavy metals during the vermiremediation sharply decreased, K and Mg decreased to a moderate extent, whereas Ca content has increased. The highest removal efficiency was detected for Ni, Co and Mn (> 80%), bioconcentration factors were as follows Zn > Co > Cu > Ni > Mn > Cr. The content of major nutrients (S, P) was substantially higher compared to the initial values. The most efficient remediation and soil quality improvement was achieved under the doses of 25–50 Mg ha-1. Higher (≥ 100 Mg ha-1) doses might restrict this technique application because of earthworm mortality and retarded growth. Overall, the study shows that vermiremediation might be a sustainable technique for ecological stabilization of SS amended soil and converting to usable for agricultural needs.
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•Earthworms reduced toxic metals soil content and increased soil fertility.•Highest vermiremediation efficiency was in soils of low-moderate SS fertilization.•Vermiremediation is limited under high SS load due to impaired earthworm performance.
The fate of diverse antibiotic resistance genes (ARGs) in anaerobic digestion (AD) system under different temperature remains largely unknow. This study employed the shotgun metagenomic sequencing ...and 16S rRNA amplicon sequencing approaches and investigated the shifts of composition and abundance of more than 1360 ARGs, as well as microbial community, in a temperature-raising AD system (from 35 °C to 55 °C) treating municipal sewage sludge. Results suggested that the six ARGs, inlcuding macB, tetA(58), bcrA, evgS, mtrA, and oleC, were predominated in digested sludge. More than 407ARG subtypes (30%) could be largely reduced under high temperature condition. Thermophilic AD (55 °C) provided a better removal for tetracycline, macrolide, penam, fluoroquinolone, acridine dye, and peptide resistance genes when compared to mesophilic AD (35 °C). The removal rates of these genes reached 29.7%–32.3%. In addition, at the end of thermophilic digestion process, the relative abundance of Firmicutes increased (from 18.22% to 74.89%), while Proteobacteria and Chloroflexi both decreased, from 36.39% to 6.80% and 20.29%–2.64%. This study further proposed the underlying mechanisms of effective elimination of ARGs under high temperature by: (1) the reduction of genes encoding antibiotic efflux pump, (2) the promotion of sludge biomass degradation rate, (3) the loss of microbial community diversity in AD systems, and (4) the inactivation of multidrug-resistant bacteria. The significance of current study is in characterizing the fate of ARGs across AD process, which allows to correlate diverse genetic properties with digesters’ operational condition. Results provided an insight into the manipulation of AD technology (e.g. temperature) to efficiently remove ARGs from municipal sewage sludge.
•Fate of ARGs in a temperature-raising anaerobic digester was investigated.•More than 1360 ARG subtypes were identified by metagenomics approach.•Effective reduction of ARGs under thermophilic condition was confirmed.•Underlying mechanisms of ARGs removal were proposed.
The simultaneous partial nitrification, anammox and denitrification (SNAD) process has been widely used in domestic sewage biological denitrification technology because of its high efficiency and low ...consumption. However, the simultaneous removal of another important pollution element, phosphorus, has been difficult, and its C/N ratio limitation of the influent is strict. The start-up of the anaerobic hydrolysis acidification (ANHA)- simultaneous partial nitrification, anammox and denitrification (SNAD)/enhanced biological phosphorus removal (EBPR) coupling process achieves the treatment of urban sewage for carbon, nitrogen and phosphorus removal. Under optimal conditions, the final total nitrogen and total phosphorus removal rates reached 91.59% and 89.10%, respectively. High-throughput sequencing technology showed that the ANHA reactor was mainly Lactococcus. At the same time, the main bacteria in the SNAD/EBPR process were anammox bacteria (AnAOB, Candidatus_Kuenenia, Candidatus_Brocadia) primarily existing in biofilms, while the ammonium oxidizing bacteria (AOB, Nitrosomonas), denitrifying polyphosphate-accumulating organisms (DPAOs, Pseudomonas, Flavobacterium, Bdellovibrio) and Denitrifying bacteria (DNB, Thauera, Denitratisoma, Rhodobacteraceae).were mainly found in the suspended sludge. These conclusions provide valuable information for the full-scale treatment of domestic sewage.
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•SNAD/EBPR process was established in a single-stage reactor using micro-oxygen.•Energy-efficient removal of TN, TP and COD in municipal sewage.•Anammox, DPAOs, NOB and AOB coexisted in single reactor.
The discharge of municipal sewage has been increasing gradually, causing great harm to the ecological environment. The study of municipal sewage treatment has received increased attention. The recent ...research progress of municipal sewage detection, treatment and reuse methods, are reviewed. However, each method has its own limitations, such as incomplete treatment, high cost and secondary pollution. This review focus on the electrochemical methods and its applications in the treatment of municipal sewage, including contaminant detection, removal of organic matter, nitrogen, phosphorus, microbial, heavy metal, and degradation of drug residues. The results from the present review demonstrate that the electrochemical technology is an advanced method for municipal sewage treatment due to the advantages of easy-operating, environmental protection and strong universality. Moreover, various new electrode materials, such as graphene, precious metals and polymers are innovated continuously, which lay a good foundation for the application of electrochemical method in municipal sewage treatment. However, some problems still exist in the industrialization of technology, comprehensive treatment of pollutants and degradation capacity of individual pollutants. Herein, some suggestions are proposed for further work of electrochemical treatment in municipal wastewater.
With the increasing production of municipal sewage sludge (MSS) in China every year, the co-firing of MSS and pulverized coal is getting more and more widely applied in large coal-fired power plants. ...The co-firing of MSS and pulverized coal will produce a large amount of particulate matter (PM) emissions, especially submicron particles. In this paper, the formation characteristics of submicron particles in the co-firing process of coal and MSS were studied in a drop tube furnace. The influence of the furnace temperature and the addition ratio of sludge on the particle size distribution and element composition of submicron particles in MSS, pulverized coal combustion and co-firing was mainly studied. The experimental results show that the furnace temperature has an influence on the formation of PM0.4. For sludge combustion, increasing the furnace temperature will promote the formation of PM0.4. The main reason is that increasing the furnace temperature promotes the gasification of Si, S, Fe, and P to form the precursor of PM0.4 or PM0.4. At same furnace temperature, the volume concentration and mass concentration of PM0.4 produced from pulverized coal combustion are less than that of sludge. Different from sludge combustion, co-firing of pulverized coal and sludge has a synergistic effect on eliminating PM0.4 formation. Increasing the addition ratio of sludge can decrease the volume concentration and mass concentration of PM0.4. This is because that aluminosilicates formed during co-firing promotes the scavenge Si, Ca, Fe, thereby reducing the precursors of PM0.4 and the mass yield of PM0.4. Increasing the furnace temperature in co-firing can inhibit the formation of PM0.4. When the furnace temperature is between 1100 °C and 1300 °C, increasing the furnace temperature will reduce the Fe content and increase the content of Si, Ca, Na, K, and P in PM0.4. However, the reduction of Fe and the increase of Si, Ca, Na, K, and P in PM0.4 offset each other, resulting in an insensitive relationship between the mass yield of PM0.4 and the furnace temperature.
•The effect of temperature and addition ratio on the formation of PM0.4 were studied.•Increasing the temperature will help the formation of PM0.4 from sludge combustion.•There is a synergistic effect exists co-combustion of coal and sludge.•Increasing the temperature for co-firing can reduce the formation of PM0.4.
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•Sedum alfredii L. (SA) and sewage sludge (MS) were co-pyrolyzed.•Blending 25% MS with SA provides optimal synergism via TG and kinetic analysis.•Co-pyrolysis enhances the yield of ...pyrolysis gas and oil.•Reaction force field simulation was used to study the interaction mechanism.•Free radicals advance the decomposition of MS and enhance the decomposition of SA.
We co-pyrolyzed municipal sewage sludge (MS) and Sedum Alfredii L. (SA, a heavy metal hyperaccumulator plant) for the first time to solve their disposal issue. Experimental and simulation results show that synergistic effects exist during the co-pyrolysis process. The thermal decomposition mechanism, kinetics, and product distribution of MS and SA at different mixing ratios (1:0, 3:1, 1:1, 1:3, 0:1) were investigated by thermogravimetric analysis and co-pyrolysis experiments. According to thermogravimetric results, the decomposition of all feedstocks can be divided into three stages. FWO method and Master plot method were used to calculate the activation energy and determine the reaction mechanism. When the addition ratio of SA was 75 %, the difference between theoretical and practical activation energies was greatest, indicating that the best synergy could be achieved at this mixing ratio. Co-pyrolysis experiment shows that more bio-oil and gas were produced. The synergistic effect between MS and different fractions of SA was studied using Reaction Force Field simulation, revealing that the free radicals generated by MS and SA advance the MS decomposition time while increasing the decomposition degree of SA. In addition, we built an artificial neural network with a 3 × 21 × 1 structure to predict the degradation process of various mixtures, which exhibits a high agreement with the experimental results. This study can provide a new idea for the disposal of SA and MS, i.e., co-pyrolysis, by solving their disposal issue while obtaining valuable products.
This study demonstrated the utilization of municipal sewage for high biomass production at large scale and achieved highest biomass yield of 46.3 tons and the lipid yield of 13.7 metric tons per acre ...in a year. The extracted crude lipid was analyzed for biodiesel production, and the yield attained was 92.5 wt% with respect to initial lipid weight. Furthermore, the lipid extracted residue obtained from two different algal biomass such as Chlorella sp. and Sargassum sp. were explored for biochar production through a slow pyrolysis technique at 400 °C. The hematite iron ore reduction with algal biochar was performed non-isothermally at 1100 °C under nitrogen atmosphere. The metallic iron synthesis from hematite iron ore involves three major steps, and they were as follows (1) in this step the Fe3O4 was synthesized from Fe2O3 at the temperature of 350–450 °C; (2) this step contain the formation of FeO from Fe3O4 at the temperature of 700–850 °C; (3) finally the formation of metallic iron (Fe) was observed at higher temperature of 850–1100 °C. Herein, we established a novel low-cost microalgae-based biorefinery approach for the production of bioenergy and residue for metallic iron production from municipal waste.
•Chlorella sp. grown in municipal sewage produced 46.3 tons/acre/year of biomass.•Autoflocculation technique was adopted and harvested the biomass upto 91%.•Lipid extracted residues produced 41 wt% of biochar after pyrolysis at 400 °C.•Chlorella biochar found as a potential material for iron (Fe) conversion from hematite.
Thermogravimetric analysis and pyrolyzer-gas chromatography/mass spectrometry measurements were taken to examine the kinetic behavior and product distribution on the thermal and catalytic pyrolysis ...of different types of sewage sludge. Compared to livestock manure sewage sludge (LMSS), municipal sewage sludge (MSS) had larger ash (30.3%) and lower fixed carbon (7.9%) contents. The peak intensities for the 1st decomposition region (200–380 °C) on the derivative thermogravimetric curve of MSS were higher than those of LMSS. In contrast, the peak height in the 2nd temperature region (>380 °C) of MSS was lower than that of LMSS. The activation energy for the pyrolysis of MSS (Avg. 186.5 kJ/mol) was lower than that of LMSS (Avg. 263.4 kJ/mol) over the entire conversion range. MSS produced larger amounts of fatty acids and cholesterol than LMSS. The in-situ catalytic pyrolysis of MSS over HBeta using a pyrolyzer-gas chromatography/mass spectrometry also produced larger amounts of aromatic hydrocarbons than LMSS, suggesting that its better feedstock properties strongly influence the final product oil quality.
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•Pyrolysis of different kinds of sewage sludge was investigated.•Municipal sewage sludge had lower activation energy during pyrolysis.•Larger amount of toluene and oleic acid was produced from municipal sewage sludge.•Catalytic pyrolysis of municipal sewage sludge over HBeta produced aromatics.
In terms of low activation energy and production of a lot of valuable chemicals, municipal sewage sludge can be a better feedstock than livestock manure sewage sludge.
•The combination of FO, RO and AnMBR for sewage treatment was analysed.•The minimum treatment cost of FO-RO + AnMBR system was estimated at 0.81 € m−3.•The minimum water production cost of FO-RO was ...estimated at 0.80 € m−3.•FO recovery was the main driver of CAPEX and OPEX.•FO membrane fluxes of 10 LMH would make the FO-RO + AnMBR system more attractive.
The economic feasibility of combining forward osmosis (FO), reverse osmosis (RO) and anaerobic membrane bioreactor (AnMBR) technologies for municipal wastewater treatment with energy and water production was analysed. FO was used to pre-concentrate the AnMBR influent, RO for draw solution regeneration and water production, and AnMBR for wastewater treatment and energy production. The minimum wastewater treatment cost was estimated at 0.81 € m−3, achieved when limiting the FO recovery to 50% in a closed-loop scheme. However, the cost increased to 1.01 and 1.27 € m−3 for FO recoveries of 80% and 90%, respectively. The fresh water production cost was estimated at 0.80 and 1.16 € m−3 for an open-loop scheme maximising water production and a closed-loop scheme, respectively. The low FO membrane fluxes were identified as a limiting factor and a sensitivity analysis revealed that FO membrane fluxes of 10 LMH would significantly improve the competitiveness of FO-RO + AnMBR technology.
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