Conventional Sewage Treatment Plant Research Articles

Performance Evaluation of conventional Sewage Treatment Plant, Iraq

One of the most pressing challenges facing contemporary health is the purification of drinking water and wastewater. Pollutants in wastewater are among the most widespread in the environment, and there is a broad spectrum of detrimental impacts associated with untreated or badly treated wastewater. The current research assessed the efficacy of the Al Rumaitha wastewater treatment facility in Muthanna province, Iraq, in eliminating municipal pollutants according to national standards. Pollutant characteristics were measured using samples taken both from the plant’s raw wastewater intake and its finished treated water output. These parameters are the Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Suspended Solids(TSS), Ammonia (NH3), Phosphorus (PO4), and the quantitative measure of the acidity or basicity (pH). According to the results, all analyses of collected samples of the plant’s effluent met the Iraqi water quality standards(IWQS) for pH, COD, BOD5, and TSS, whereas the values of NH3 and PO4 did not reach the (IWQS) in all months. where mean monthly removal efficiencies of 86% for BOD5, 80% for COD, 93% for TSS, 39% for PO4, and 27% for NH3 were achieved. Briefly, it can be said that the Al-Rumaitha WWTP has an acceptable level of efficacy in treating wastewater for some of the examined parameters and providing water in line with Iraqi environmental regulations, but not for others.

Infilling missing data and outliers for a conventional sewage treatment plant using a self-organizing map: a case study of Kauma Sewage Treatment Plant in Lilongwe, Malawi

Abstract Data availability is key for modeling of wastewater treatment processes. However, process data are characterized by missing values and outliers. This study applied a self-organizing map (SOM) to fill in missing values and replace outliers in wastewater treatment data from Kauma Sewage Treatment Plant in Lilongwe, Malawi. We used primary and secondary wastewater data and executed the SOM algorithm to fill missing values and replace outliers in effluent pH, biochemical oxygen demand, and dissolved oxygen. The results suggest that the SOM algorithm is reliable in filling gaps in wastewater time series data with less than 50% missing values with correlation coefficient (R) values of >0.90. The SOM algorithm failed to reliably fill gaps and replace outliers in time series data with >50% missing values. For instance, high mean square error (MSE) values of 3,655.57, 10.62, and 2,153.34 for pH, DO, and BOD, respectively, were registered in datasets with more than 50% missing values, while very small MSE values (MSE ≈ 0) were associated with effluent pH, BOD, and DO data with missing values of >50%. Practitioners can use this approach to improve the planning and management of wastewater treatment facilities where available data records are riddled with missing observations.

Design of 50KLD MBBR based Sewage Treatment for Hostel Building, Nagpur

Abstract: Sewage water recovery is the treatment or processing of Sewage water to make it applicable. This paper shows the design of various component of conventional sewage treatment plant using Moving Bed Biofilm Reactor technique at College Hostel, Nagpur. The project consisting of the design of complete Sewage Treatment Plant components consist of Bar Screen Chamber, Equalization Tank, Aeration Tank, Clarifier Tank, Pressure Sand filter, Activated Carbon Filter and Treated Water Tank. Among the available technologies for waste water treatment, MBBR sewage treatment is most suitable. It is a leading technology in waste water treatment as this system can operate at lower vestiges and give advanced efficiency of treatment. It’s compact and effective option for domestic waste treatment. In duly designed MBBR, the whole reactor volume is active, with no dead space or short circuiting. This paper demonstrates the detailed procedure for the design of a MBBR grounded sewage treatment plant of 50 KLD capacity for an educational lot.

Environmental sustainability assessment of captive conventional sewage treatment plant designs

Environmental sustainability assessment of captive conventional sewage treatment plant designs

Feasibility of a Novel (SHEFROL) Technology in Pre-Treating Eatery Wastewater at Pilot Scale

The wastewater ensuing from public eateries is higher in its chemical and biological oxygen demand (COD and BOD) as also its oil, grease, and protein content than sewage. For this reason such wastewater is much harder to treat; its content of fats, proteinaceous material, and xenobiotics mounting major challenges. But in most of the developing world about 80% of such wastewater is discharged untreated and the remaining is mixed with sewage going to the treatment plants. This happens due to the prohibitively high cost of treatment that is entailed if these wastewaters are to be treated by conventional activated sludge processes (ASPs) or a combination of anaerobic digestion and ASPs. The practice of allowing eatery wastewater to join sewage en route sewage treatment plants increases the load on the latter, especially due to the high fat and protein content of the former. The present work describes attempts to use the recently developed and patented SHEFROL® technology in affecting treatment of wastewater coming from a typical eatery. After establishing feasibility at bench scale, the process was tested in a case study at pilot plant scale for treating 12,000 litres/day (LPD) of wastewater being generated by the eateries situated in the campus of Pondicherry University, India. The capacity of the pilot plant was then expanded to 30,000 LPD. Despite operating the units at a very low hydraulic retention time (HRT) of 2 ± 0.5 h, due to the limitations of land availability, which translates to a rate about three times faster than a typical ASP, over 50% removal of COD and BOD, and similarly substantial removal of other pollutants was consistently achieved. Given that the SHEFROL units can be set up at a negligible cost, the findings indicate that SHEFROL technology can be used to significantly yet inexpensively pre-treat eatery wastewaters before either sending them for further treatment to conventional sewage treatment plants, higher-end SHEFROL units, or discharging them directly if neither of the other two options is available.

Enhanced biological nitrogen and phosphorus removal from sewage driven by fermented glycerol: comparative assessment between sequencing batch- and continuously fed-structured fixed bed reactor.

The nutrient biological removal from sewage, especially from anaerobic reactor effluents, still represents a major challenge in conventional sewage treatment plants. In this work, the nitrogen and phosphorus removal from anaerobic pre-treated domestic sewage in an up-flow anaerobic sludge blanket (UASB) reactor was assessed in a structured fixed bed reactor (SFBR) operated in a continuous and in a batch mode using polyurethane foam as material support for biomass and fermented glycerol as the exogenous carbon source. The SFBR was operated as a sequencing batch reactor with cycles of 90, 120, and 150min under anaerobic, oxic, and anoxic conditions, respectively, reaching average efficiencies for total nitrogen and phosphorus removal of 88% and 56%, respectively. Fermented glycerol was added during the non-aerated periods. Under continuous feeding, the SFBR was operated with aeration/non-aeration periods of 2/1 (h) and 3/1 (h), hydraulic retention time of 12h, and a recirculation ratio of 3. Without fermented glycerol addition, the maximum removal of total nitrogen (TN) reached 42%, while adding glycerol in the non-aerated period improved TN removal to 64.9% (2/1h) and 69.5% (3/1h). During continuous operation, no phosphorus removal was observed, which was released during the non-aerated period, remaining in the effluent. Optical microscopy analyses confirmed the presence of polyphosphate granules and of the phosphorus accumulating organisms in the reactor biofilm. It was concluded that the batch feeding method was determinant for phosphorus removal. The structured fixed bed reactor with polyurethane foam proved to be feasible in the removal of organic matter and nutrients remaining in the UASB reactor effluent.

Comparative evaluation of the macrophytes in the constructed wetlands for the treatment of combined wastewater (greywater and septic tank effluent) in a sub-tropical region

The role of macrophytes in constructed wetlands (CW) has been studied extensively in the last three decades. The remediating effect of macrophytes in CWs depends on whether the species is suitable for the given climatic and operational conditions and on the morphological traits of the species. This study experimentally investigated and compared the contribution of three macrophytes, namely Phragmites karka, Iris kashmiriana, and Sagittaria latifolia in removing pollutants from combined wastewater (greywater and septic effluent) using horizontal sub-surface flow type constructed wetlands (HSSF-CW) under sub-tropical conditions. The study monitored the standard wastewater parameters (COD, Nitrogen, Phosphorus, and Solids) in the inlet and outlet of the CW microcosms, the fate of nutrients through the planted microcosms, and the growth rate of the selected species. Phragmites karka showed better removal efficiencies than the other two species, with organic loading removal rates of 10 ± 1.3 gm−2d−1, nitrogen removal rates of 2.6 ± 0.4 gm−2d−1, phosphorus removal rates of 1.3 ± 0.2 gm−2d−1, and solids removal rates of 3.6 ± 1.2 gm−2d−1. Mass balance showed that the nutrient uptake by species Sagittaria latifolia (TP – 9.3 g and TN – 48.2 g) was the most, followed by Phragmites karka (TP – 8.6 g and TN – 47.9 g) and Iris kashmiriana (TP – 4.4 g and TN – 29.1 g). Biomass analysis revealed that Phragmites karka had the maximum biomass growth rate with an increment of 1383 gm−2: 524 gm−2 in the above-ground: below ground dry biomass weight, while as Sagittaria latifolia and Iris kashmiriana showed an increase of 1299 gm−2: 866 gm−2 and 663 gm−2: 1312 gm−2, respectively. The macrophytes with well-developed root systems (Phragmites karka) had a better pollutant remediating effect. The nutrient uptake by macrophytes depended on the total dry biomass increase and the nutrient content of the biomass. The CW beds of the three macrophytes need nutrient pre- or post-treatment to comply with the irrigation reuse and conventional sewage treatment plant (STP) discharge regulations in India.

Evaluation of the occurrence of antibiotics at different treatment stages of decentralised and conventional sewage treatment plants

Evaluation of the occurrence of antibiotics at different treatment stages of decentralised and conventional sewage treatment plants

Metoprolol and Its Degradation and Transformation Products Using AOPs-Assessment of Aquatic Ecotoxicity Using QSAR.

Pharmaceuticals are found in waterbodies worldwide. Conventional sewage treatment plants are often not able to eliminate these micropollutants. Hence, Advanced Oxidation Processes (AOPs) have been heavily investigated. Here, metoprolol is exposed to UV irradiation, hydrogen peroxide, and ozonation. Degradation was analyzed using chemical kinetics both for initial and secondary products. Photo-induced irradiation enhanced by hydrogen peroxide addition accelerated degradation more than ozonation, leading to complete elimination. Degradation and transformation products were identified by high-performance liquid-chromatography coupled to high-resolution higher-order mass spectrometry. The proposed structures allowed to apply Quantitative Structure-Activity Relationship (QSAR) analysis to predict ecotoxicity. Degradation products were generally associated with a lower ecotoxicological hazard to the aquatic environment according to OECD QSAR toolbox and VEGA. Comparison of potential structural isomers suggested forecasts may become more reliable with larger databases in the future.

Enhancing Microplastics Removal from Wastewater Using Electro-Coagulation and Granule-Activated Carbon with Thermal Regeneration

Discharge from sewage treatment plants (STPs) is a significant pathway of entry for microplastics (MPs) to the environment. Therefore, STPs should be considered as an important barrier to the distribution and circulation of MPs in the aquatic environment. In this study, the fate and material-specific properties of MPs were investigated in an STP-equipped and granule-activated carbon (GAC) tower with a thermal regeneration system. This system functioned with a tertiary treatment unit. The GAC with thermal regeneration removed 92.8% of MPs and was useful for removing MPs with a specific gravity less than that of water and with a size of 20–50 µm, which had negligible removal in the conventional STP process. In addition, a lab-scale electric-coagulation experiment was conducted to examine its potential utility as a pretreatment process for further enhancing the removal efficiency of MPs by GAC. After 30 min of electro-coagulation using aluminum electrodes, 90% of MPs were converted into separable flocs by centrifugation. These flocs may be effectively removed by GAC or other tertiary treatment steps. This study demonstrates that GAC with thermal regeneration is a tertiary process that can efficiently prohibit the release of MPs from STPs and circulation of MPs in the natural environment.

Removal of two cytostatic drugs: bleomycin and vincristine by white-rot fungi \u2013 a sorption study

PurposeCytostatic drugs cannot be easily removed by conventional sewage treatment plants, resulting in their ultimate release into aquatic systems where they become a threat. Thus, new technologies which can be used to eliminate these drugs more effectively before they enter the environment are increasingly important. Fungal treatment of wastewaters is a promising and environmentally friendly technology for pharmaceutical remediation. The aim of this work is to examine the biosorption of two cytostatics, bleomycin and vincristine, in the aqueous solution by fungal biomass.MethodsFive white-rot fungi were used in this study: Fomes fomentarius (CB13), Hypholoma fasciculare (CB15), Phyllotopsis nidulans (CB14), Pleurotus ostreatus (BWPH), and Trametes versicolor (CB8). Tests were conducted on different types of biomass (alive and dead – autoclaved) and in various physico-chemical conditions: varied drug concentrations (5, 10 and 15 mg/L), temperatures (from 15.4 to 29.6 °C), and pH (from 3.2 to 8.8).ResultsThe results showed that among alive biomass, T. versicolor (CB8) had the greatest sorption ability for bleomycin and P. nidulans (CB14) worked best for vincristine. The tested sorption process could be described by a pseudo-second order kinetics model. Sorption equilibrium studies demonstrated that for bleomycin Redlich-Peterson, while for vincristine Langmuir model fitted best. The thermodynamic studies showed that the sorption process was endothermic chemisorption for bleomycin, and exothermic physisorption for vincristine. For both drugs the sorption ability increased with an increase of the pH value.ConclusionThe biosorption on fungal biomass is a favorable alternative to conventional wastewater treatment processes for anticancer drug removal.

SDG Implementation through Technology? Governing Food-Water-Technology Nexus Challenges in Urban Agriculture

The 2030 Agenda for Sustainable Development emphasizes the importance of technology as a pillar for the implementation of the Sustainable Development Goals (SDGs). Technology innovation promises benefits especially for the implementation of SDG 2 to end hunger, achieve food security and improved nutrition, and promote sustainable agriculture. Contributing to current debates on SDG implementation, technology innovation, and cross-sectoral governance, we argue that technology innovation carries both the potential to contribute to global goal implementation and the risk of posing new governance challenges. Applying a food-water-technology nexus (FWTN) perspective, we conduct a case study on an emerging technology in urban agricultural production in Germany. The technology connects the wastewater treatment system and the agricultural production system and projects the transformation of a conventional sewage treatment plant into a ‘NEWtrient®-Center,’ which draws the essential resources for urban hydroponic plant cultivation from municipal wastewater. Building on qualitative and participatory research methods, the study provides deeper insights into the governance implications of FWTN issues stemming from the emerging technology. The analysis shows that this technology has the potential to facilitate SDG implementation, but simultaneously fuels new sector interlinkages between water and food and policy demands that substantiate the need for more integrated policymaking to ensure the smart use of technology to reach the SDGs.

Upgradation of conventional MBBR into Aerobic/Anoxic/Aerobic configuration: A case study of carbon and nitrogen removal based sewage treatment plant

The thrust of this study was to assess the upgradation of an existing 3.5 million liters per day (MLD) full-scale conventional MBBR-based sewage treatment plant (STP) into Aerobic/Anoxic/Aerobic configuration. Initially, the plant was designed and constructed for achieving BOD and TSS to <30 mg/L and <50 mg/L, respectively. Recently, due to the advent of stringent effluent standards for BOD (Biological Oxygen Demand), TSS (Total Suspended Solids), and TN (Total Nitrogen) to <10 mg/L, with a strong emphasis on non-potable re-use of treated effluent, the existing system needed intensive upgradation. The upgraded STP was modified from two hours to five hours of hydraulic retention time (HRT). The upgraded plant was examined by removing organic carbon and nitrogen from municipal wastewater through both partial nitrification-denitrification (PND) by aerobic and anoxic reactors and simultaneous nitrification and denitrification (SND) process by PVA (Poly Vinyl Alcohol) gel aerobic reactor. After ten months of operation and monitoring, the plant has reached its upgraded effluent discharge standard. It was found that average BOD, COD, TSS, TN, and TP (Total Phosphorus) concentrations were 8 mg/L, 25 mg/L, 12 mg/L, 9 mg/L and 5 mg/L respectively, with 91 %, 90 %, 93 %, 84 %, and 64 %, removal efficiency. It was observed that PVA-gel beads are not only efficient for carbon removal (BOD & COD) but also achieve high SND rates.

Analysis of Microbial Communities and Pathogen Detection in Domestic Sewage Using Metagenomic Sequencing

Wastewater contains diverse microbes, and regular microbiological screening at wastewater treatment plants is essential for monitoring the wastewater treatment and protecting environmental health. In this study, a metagenomic approach was used to characterize the microbial communities in the influent and effluent of a conventional domestic sewage treatment plant in the metropolitan city of Jeddah. Bacteria were the prevalent type of microbe in both the influent and effluent, whereas archaea and viruses were each detected at &lt;1% abundance. Greater diversity was observed in effluent bacterial populations compared with influent, despite containing similar major taxa. These taxa consisted primarily of Proteobacteria, followed by Bacteroidetes and Firmicutes. Metagenomic analysis provided broad profiles of 87 pathogenic/opportunistic bacteria belonging to 47 distinct genera in the domestic sewage samples, with most having &lt;1% abundance. The archaea community included 20 methanogenic genera. The virus-associated sequences were classified mainly into the families Myoviridae, Siphoviridae, and Podoviridae. Genes related to resistance to antibiotics and toxic compounds, gram-negative cell wall components, and flagellar motility in prokaryotes identified in metagenomes from both types of samples. This study provides a comprehensive understanding of microbial communities in influent and effluent samples of a conventional domestic sewage treatment plant and suggests that metagenomic analysis is a feasible approach for microbiological monitoring of wastewater treatment.

Cultivation of anaerobic ammonium oxidizing bacteria (AnAOB) using different sewage sludge inoculums: process performance and microbial community analysis

AbstractBACKGROUNDThis study explores the feasibility of three different inoculum sources (anaerobic, aerobic, and anoxic sludge from conventional sewage treatment plants) together with the potential of biomass carrier for Anaerobic ammonium oxidation bacteria (anammox) cultivation. Fed‐batch reactors were operated with synthetic medium at different temperatures.RESULTSThe reactor inoculated with anaerobic sludge and biomass carrier showed close to stoichiometric nitrite to ammonia utilization (1.2:1) and the highest ammonia removal (12.2 mg NH4+·g VS−1·day−1), followed by the reactor inoculated with activated sludge without carrier (4.3 mg NH4+·g VS−1·day−1), which also showed close to stoichiometric nitrite to ammonia utilization. Anammox development was recorded by higher nitrogen removal, gradually increasing gas production rate, and the presence of Brocadiaceae anammox family bacteria. All batch reactors revealed significant phosphorus removal (&gt;80%), which was attributed to the co‐existence of anammox bacteria (Brocadiaceae) with denitrifying polyphosphate accumulating organisms (flavobacterium sp.).CONCLUSIONThe results of this study revealed that anaerobic sludge and activated sludge from sewage treatment plants with biomass carriers for microbial immobilization were suitable for anammox bacteria enrichment. The co‐existence of anammox bacteria with denitrifying polyphosphate accumulating microorganisms reveals new possibilities for simultaneous nitrogen and phosphate removal. © 2020 Society of Chemical Industry (SCI)

Fabrication and characterization of a thin coated adsorbent for antibiotic and analgesic adsorption: Experimental investigation and statistical physical modelling

Sulfamethoxazole (antibiotic) and acetaminophen (analgesic) are classed as common Contaminants of Emerging Concern (CEC) that have been detected in significant quantities in sewage treatment plants in Malaysia and other countries. Unfortunately, the conventional sewage treatment plants are not effective to reduce the concentrations of these compounds. Therefore, this study introduces a novel Contaminant Emerging Remover (COATER) to face the pollution caused by these CECs. This COATER was formulated using epoxidized neutral rubber (ENR-50) and poly(vinyl) chloride (PVC) as binders besides activated carbon as an adsorbent, which was coated on white cotton fabric (substrate) via brushing technique. Characterization analysis of this COATER was performed using SEM-EDX, FTIR and BET quantifications to study the surface chemistry and to obtain insights about the adsorption mechanism. Results of surface morphology analysis showed a good distribution of activated carbon onto the substrate where the surface area and pore volume of the COATER were 64.3 m2/g and 0.07 cm3/g, respectively. Adsorption isotherms of tested CECs on COATER were experimentally quantified at different temperatures. A monolayer adsorption model based on statistical physics was used to understand the adsorption mechanism. Modelling results showed that the adsorption orientation of tested molecules was similar but it could occur a change in the interaction of these pollutants with the adsorption sites of COATER surface during the removal process since this adsorbent contained a variety of functional groups. It was concluded that the adsorption mechanism of tested adsorbates on COATER included pore interaction, chemical bonding and electrostatic forces.

Development of an up-flow anoxic nano-biotechnological reactor for simultaneous removal of ammonia and COD from low C/N secondary treated wastewater

Fe3+ reduction coupled to nitrification and Fe2+ oxidation coupled to denitrification, occurring in anoxic sediments of aquatic ecosystems, play an important role in global nitrogen cycle. Till date, limited research was done in applying this phenomenon to wastewater treatment. In this study, we fabricated and evaluated an anoxic up-flow packed bed continuous reactor that mimics the Fe redox cycle coupled to microbial mediated simultaneous removal of NH4+-N and COD. The process was initially developed using synthetic wastewater and was later applied to treat low C/N secondary treated wastewater generated from a conventional sewage treatment plant in Chennai, India. Studies were carried out for 500 days to evaluate the performance of the novel process using laboratory synthesized Granulated Nanoscale Oxyhydroxides of Fe (GNOF) as electron acceptor in a 3.92 L capacity anoxic up-flow packed bed reactor. The reactor was operated at different loading rates by varying the Hydraulic Retention Time (HRT) between 24 h and 4 h. Enhanced removals of NH4+-N (93.20 ± 2.37 %), TN (86.45 ± 6.04 %), and COD (66.47 ± 13.90 %) were attained at 12 h HRT as a result of co-existence of ammonia oxidizing bacteria, denitrifiers, and anammox species. Enhanced performance was obtained by evolving anammox in a gradient of NH4+-N and NO2−-N in the reactor. This work demonstrates the use of GNOF for the first time in continuous packed bed reactor for the anoxic removal of NH4+-N and COD from secondary treated wastewater. This process holds economic advantages compared to other biological nitrogen removal techniques: (i) as the requirement of oxygen is substituted by GNOF, (ii) occurrence of simultaneous nitrification and denitrification in the single reactor maintains the pH and hence alkalinity addition is not required, and (iii) sludge disposal costs are less. The recycling of GNOF inside the reactor makes this process more sustainable and suitable for practical applications.

Carbamazepine Ozonation Byproducts: Toxicity in Zebrafish (Danio rerio) Embryos and Chemical Stability.

Carbamazepine (CBZ) is an anticonvulsant medication with highly persistent properties in the aquatic environment, where it has the potential to affect nontarget biota. Because CBZ and many other pharmaceuticals are not readily removed in conventional sewage treatment plants (STP), additional STP effluent treatment technologies are being evaluated and implemented. Whole effluent ozonation is a prospective method to remove pharmaceuticals such as CBZ, yet knowledge on the toxicity of CBZ ozonation byproducts (OBPs) is lacking. This study presents, for the first time, in vivo individual and mixture toxicity of four putative OBPs, that is, carbamazepine 10,11-epoxide, 10,11-Dihydrocarbamazepine, 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM), and 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-dione (BQD) in developing zebrafish (Danio rerio) embryos. BQM and BQD were isolated from the ozonated solution as they were not commercially available. The study confirmed that the OBP mixture caused embryotoxic responses comparable to that of ozonated CBZ. Individual compound embryotoxicity assessment further revealed that BQM and BQD were the drivers of embryotoxicity. OBP chemical stability in ozonated CBZ water solution during 2 week dark storage at 22 °C was also assessed. The OBP concentrations remained over time, except for BQD which decreased by 94%. Meanwhile, ozonated CBZ persistently induced embryotoxicity over 2 week storage, potentially illustrating environmental concern.

Wet Peroxide Oxidation of Paracetamol Using Acid Activated and Fe/Co-Pillared Clay Catalysts Prepared from Natural Clays

Many pharmaceuticals have been recently identified at trace levels worldwide in the aquatic environment. Among them, the highly consumed paracetamol (PCM), an analgesic and antipyretic drug, is largely being accumulated in the aquatic environment due to inefficient removal by conventional sewage treatment plants. This work deals with the treatment of PCM, used as a model pharmaceutical contaminant of emerging concern, by catalytic wet peroxide oxidation using clay-based materials as catalysts. The catalysts were prepared from natural clays, extracted from four different deposits using acid-activated treatment, calcination, and pillarization with Fe and Co. Pillared clays show the highest catalytic activity owing to the presence of metals, allowing to remove completely the PCM after 6 h under the following operating conditions: CPCM = 100 mg L−1, CH2O2 = 472 mg L−1, Ccat = 2.5 g L−1, initial pH = 3.5 and T = 80 °C. The prepared materials presented high stability since leached iron was measured at the end of reaction and found to be lower than 0.1 mg L−1.

Occurrence of microplastics in municipal sewage treatment plants: a review.

Municipal sewage treatment plants (STPs) are thought to be important point sources of microplastics in freshwater systems and many peer-reviewed articles have been published on this issue since mid-2010s. In this review, we summarize existing literature on the occurrence of microplastics in STPs and experimental methods used for isolation and identification of microplastics. The number concentrations of microplastics in STP influents were 15.1-640 L-1, whereas those in the STP effluents were highly variable and ranged from not detectable to 65 L-1. For most of cases, conventional STPs are removing microplastics very effectively. Fragments and fibers are dominant shapes of microplastics. Thermoplastics (polyethylene and polypropylene) and polyester are the predominant materials recovered. Although further research is needed, size distribution of microplastics in STPs is likely to follow a power law, implying that different studies using different size cutoffs may be compared after establishing a power law relationship.