Domestic Sewage Treatment Plant Research Articles

Tracing phosphorus sources in the river-lake system using the oxygen isotope of phosphate

The biogeochemical cycling of phosphorus (P) in river-lake systems presents significant challenges in tracing P sources, highlighting the importance of effective traceability approaches for formulating targeted management measures to mitigate lake eutrophication. In this study, we used the oxygen isotope of phosphate (δ18Op) as a tracer in the river-lake systems, establishing a tracing pathway from potential end-members, through inflow rivers, and eventually to the lake. Taking Dianshan Lake and its main inflow rivers as the study area, we measured δ18Op values of potential end-members, including domestic sewage treatment plant effluents, industrial effluents from phosphorus-related enterprises (printing and dyeing, electroplating, plastics, etc.), and farmland soils. Notably, the industrial effluent signatures ranged from 13.1 ‰ to 21.0 ‰ with an average of 16.8 ‰ ± 3.2 ‰, enriching the δ18Op threshold database. Using the MixSIAR model, it was found that phosphorus in the Jishuigang River primarily originated from agricultural non-point sources and domestic sewage in the dry season, while the Qiandengpu River, with a higher proportion of urban area, had a greater influence from domestic sewage and industrial effluents. Moreover, significant differences were observed between δ18Op values at the lake entrances of the inflow rivers (13.7 ‰ ± 1.0 ‰) and in acid-soluble phosphate of the lake sediments (9.9 ‰ ± 1.0 ‰). Isotopic tracing revealed that phosphorus in the lake originated from both external inputs (80.6 %) and internal release (19.4 %) in the dry season. Alongside pollutant flux calculations based on the hydrological conditions and water quality of the inflow rivers, our findings indicated that phosphorus in Dianshan Lake was mainly attributed to agricultural non-point sources, domestic sewage and sediment release in the dry season. This study provided novel insights into the identification of pollution sources in the river-lake systems, with broad implications for pollution control and environmental protection.

An effective way to utilize solid waste resources: The application of modified fly ash in removing Cu2+ and Pb2+ in wastewater

The sustainable development of society requires the support of developed industrial production, which inevitably produces a series of industrial by-products, including heavy metal-containing wastewater and solid waste. Using solid waste to adsorb heavy metal ions in wastewater is a sustainable way. This not only reduces the environmental threat caused by solid waste accumulation, but also reduces the treatment cost of heavy metal ions in wastewater. In this study, fly ash was modified to prepare magnetic adsorbent (M-AT), which was used to adsorb Cu2+ and Pb2+ in wastewater. The results showed that M-AT has a good adsorption effect on Cu2+ and Pb2+ in wastewater. Its maximum adsorption capacity for Cu2+ and Pb2+ was 53.18 and 85.86 mg/g, respectively. Ion exchange and complexation reaction were major adsorption mechanisms of M-AT for Cu2+ and Pb2+, they played an important role in the adsorption process. M-AT maintained a good adsorption effect on Cu2+ and Pb2+ under different influence factors. This ensured that M-AT can be used in complex application environments. In addition, M-AT exhibited good reusability, its removal rate for Cu2+ and Pb2+ reached 50.21 % and 75.15 % after 5 adsorption–desorption cycles. And the removal rate of M-AT for Cu2+ and Pb2+ in domestic sewage treatment plant influent, tailings drainage, industrial wastewater was 82.80 %, 87.12 %, 85.12 % and 95.10 %, 91.20 %, 93.13 %, respectively. These results proved the feasibility of M-AT in treating Cu2+ and Pb2+ in wastewater. This study provides a new way for the resource utilization of fly ash. Applying solid waste to treat heavy metal-containing wastewater is a sustainable way to treat industrial waste.

Photocatalytic application towards the degradation of ciprofloxacin and algae by Z-scheme 2D/3D heterojunction of Bi12O17Cl2/UiO-66-NH2

With the continuous emergence of antibiotics in natural water bodies, the crisis of water environment is becoming increasingly serious. To efficiently remove antibiotics, a novel 2D/3D Z-scheme heterojunction of Bi12O17Cl2/UiO-66-NH2 was constructed by in situ growth technology. The formation of Z-scheme heterojunction between Bi12O17Cl2 and UiO-66-NH2 not only significantly improves the transfer rate and separation efficiency of charge carriers, but also greatly prolongs the lifetime of electrons and improves their light absorption ability. Free radical capture experiments and ESR spectra display that ⋅O2− and ⋅OH radicals dominate the degradation process of ciprofloxacin. The synthesized Z-scheme heterojunction shows a high degradation rate of 83.5 % for antibiotic ciprofloxacin within 60 min, much higher than those of Bi12O17Cl2, UiO-66-NH2 monomers and many other reported photocatalysts. The heterojunction Bi12O17Cl2/UiO-66-NH2 also exhibits excellent degrading performance towards antibiotics in three actual water bodies (tap water, lake water and the effluent of domestic sewage treatment plant). Meanwhile, the as-prepared photocatalyst can effectively degrade Microcystis aeruginosa and algal toxin Microcystin-LR in surface water bodies contaminated by algae and antibiotics. The QSAR analysis indicates that the toxicities of both ciprofloxacin and its intermediates are greatly reduced. The degradation pathways of ciprofloxacin were analyzed via Density Functional Theory calculations and QSAR analysis. This study provides an excellent synthesis method of Z-scheme heterojunction for the purification of surface water bodies contaminated by algae and antibiotics via photocatalytic technology.

Optimal Operation of Domestic and Industrial Sewage Treatment Plants Using Machine Learning Methods

Purpose: This study aims to determine the economic and technical feasibility of operating and leasing sewage treatment plants through an application that uses mathematical modeling and Machine Learning techniques for process optimization. Theoretical Framework: Efficient operation of sewage treatment plants (STPs) is crucial to ensure water quality, minimize environmental impacts, and optimize costs. This study explores how Machine Learning (ML) can model and optimize sewage treatment processes, adapting to real-time conditions. Method/Design/Approach: The BSM1 model is combined with Machine Learning techniques to create simplified metamodels, enabling optimized results and the development of an application for evaluating economic and technical outcomes. Results and Conclusion: The reduced metamodel successfully reproduced the Simulink model, achieving satisfactory optimization. Research Implications: This research benefits water quality improvement, cost reduction, sustainability, innovation, water resource management, awareness, and resilience to extreme weather events, as well as influencing informed policies. Originality/Value: Efficiency, sustainability, economy, and quality of life are core values in this research, benefiting society, the environment, and the economy.

Analysis of the Potential for Reusing Sanitary Effluents in the Hydrographic Basin of the Ipojuca River

Objective: This study aims to present an assessment of the potential for reusing effluents from domestic sewage treatment plants in the Hydrographic Basin of the Ipojuca River. Theoretical Framework: In regions facing water scarcity, effluent reuse emerges as an alternative to alleviate pressures and reduce contamination of water sources. In this regard, the choice of the Ipojuca River Watershed is justified due to the susceptibility of its constituent municipalities to water scarcity and pollution, as well as the fact that the Ipojuca River has been classified as the third most polluted in the country. Methodology: The methodology involved basin characterization, data collection from the sanitation services provider to perform quantitative and qualitative evaluation of reclaimed water supply, identification of demands based on consumptive uses (industry and irrigation), existing water use permits, and the provider's customer database. Additionally, georeferenced maps were generated for spatial analysis of the water balance. Results and Conclusion: Twelve Sewage Treatment Plants were identified, four of which are still under construction, with nominal treatment capacities exceeding the identified irrigation and industrial demands, except for two of them. In terms of quality, for the analyzed parameters, the treatment plants demonstrated satisfactory performance, suggesting that the effluent could be utilized for restricted purposes without the need for further treatment. Lastly, geospatially, the demands are located within a radius of 10km from the analyzed plants, in most cases. Research Implications: It can be inferred that the basin holds a significant reuse potential to be explored as an alternative for enhancing water availability and reducing effluent discharge into the Ipojuca River. Originality/Value: The results obtained through this unprecedented analysis in the watershed serve as a reference for policymakers and implementers of water resources management policies, as well as an encouragement for potential producers and consumers of reclaimed water.

Abundance, characteristics and seasonal variation of microplastics in a domestic sewage treatment plant in Nanjing, China

Sewage treatment plants are a potential route of microplastics (MPs) into the environment, hence it's urgent to investigate MPs in wastewater and sludge through lengthy sampling campaigns. In this study, a sewage treatment plant in Nanjing, China was chosen, seasonal variation of MPs in influent was analyzed by collecting samples during a 12-month sampling campaign (at monthly intervals over a one-year period). Abundance and characteristic of MPs from different treatment stages were also investigated. The results showed that there was a seasonal variation in the amount of MPs in influent and the abundance of MPs was significantly greater in summer than other seasons. The average MPs abundance was 41.0 items/L and 3.0 items/L in influent and effluent, with a total 92.6 % removal rate. Overall, 125–355 μm were the main size in each treatment section, with fibers dominant shape and transparent main color. Additionally, the primary polymer compositions of MPs were polyethylene (PE) and polypropylene (PP) using micro-Roman spectroscopy. The daily MPs emission from effluent and sludge was estimated to be 300 million and 1274 million items/d, demonstrating that the sewage treatment plant is an important source of MPs into the environment despite the high removal rate of MPs.

Água residuária e substratos no crescimento de mudas de angico

ABSTRACT The production of seedlings of forest species for reforestation of biomes is a practice that restores the conditions of the environment, but water and substrates that favor the growth of seedlings are required. However, in the semi-arid region, water is a limiting factor, requiring the use of alternative sources such as treated domestic sewage. In this context, the objective was to evaluate the growth of Anadenanthera colubrina L. seedlings produced in substrates (soil + bovine manure and soil + coconut fiber) fertilized with treated domestic sewage effluent diluted in public-supply water in proportions (100, 75, 50 and 25% of domestic effluent) and using water from the supply network as a control. The treatments were arranged in a completely randomized design, in a split-plot with three replicates. The treated domestic effluent (TDE) used in the experiment came from the domestic sewage treatment plant of the decanter-digester type of the Projeto de Assentamento Milagre Apodi/RN. The study was conducted in a seedling production nursery at UFERSA, with growth and vigor evaluations at 30, 60, 90 and 120 days after transplanting. The production of seedlings fertigated with domestic effluent caused differences in all growth variables, with improvement in phytomass production. Seedlings fertigated with a dilution of 50% TDE and 50% water supply showed better results when produced with substrate composed of soil and coconut fiber. The seedlings showed good quality, and those cultivated with 50% and 75% of wastewater showed better quality after 120 days of cultivation.

Distribution of Antibiotic Resistance Genes and Their Association with Microbes in Wastewater Treatment Plants: A Metagenomics Analysis

The extensive use of antibiotics has resulted in the generation and accumulation of antibiotic resistance genes (ARGs) in the environment, and domestic wastewater is one of the main reservoirs of ARGs and resistant bacteria. In this study, Illumina high-throughput sequencing and network analysis were used to study the microbial community characteristics, ARGs’ occurrence status, and resistance mechanism in the influent and effluent of a domestic sewage treatment plant in Changchun, China. A total of 29 phyla were found in the influent and effluent, including 23 bacterial phyla, 3 archaeal phyla, and 3 eukaryotic phyla. In total, 112 ARG subtypes were detected in the samples, and the dominant ARG subtypes were Erm(35) and tet(W/N/W). In this study, ARGs related to tetracycline and macrolide accounted for a high proportion, and the resistance mechanisms of ARGs detected in the samples were mainly antibiotic inactivation and antibiotic efflux pumps. Co-occurrence maps of ARGs and microbes demonstrated by network analysis indicated that the resistance genes kdpE, GES-5, and tetX may easily bind to microbes, potentially making them antibiotic-resistant bacteria. Fifty-seven bacteria in the genera Cupriavidus, Escherichia, and Collinsell are potential hosts of multiple ARGs. The findings can increase our understanding of the distribution of ARGs and their association with microbes in wastewater treatment plants, and also provide a research foundation for controlling the diffusion of ARGs in the environment.

Mitigation of Antimicrobial Resistance during Wastewater Treatment by Membrane Technologies

The threat of antimicrobial resistance (AMR) to human health is predicted to become a significant infectious disease. Domestic sewage and wastewater treatment plants (WWTPs) are critical hotspots for controlling the spread of antibiotic resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) in the environment. A wastewater treatment system is not necessarily designed to mitigate AMR problems in wastewater. Furthermore, the presence of ARB and ARGs for a long time in WWTPs is reported as a reservoir of intracellular and extracellular ARG through horizontal gene transfer. Based on the studies, the additional membrane filtration with either microfiltration (MF) or ultrafiltration (UF) can reduce ARB and ARGs effectively through the separation mechanism. However, there are still inconclusive results when comparing ARG removal efficiencies between MBR and conventional processes. Further studies are required to clarify the effect of water qualities and membrane fouling conditions on ARG removal.

Assessment of Heavy Metal Concentrations in Penang, Malaysia’s Wastewater Treatment Plants: A Wastewater-Based Epidemiology Approach

Heavy metals and trace metals are among the most prevalent contaminants in sewage. Depending on the concentration and frequency of exposure, certain heavy metals are toxic, carcinogenic, and hazardous to humans. In this study, copper (Cu), nickel (Ni), zinc (Zn), iron (Fe), and cadmium (Cd) levels were measured in the collected wastewater samples from 10 selected domestic sewage treatment plants (STPs) in Penang, Malaysia in December 2021. All metals in the wastewater were determined using the atomic absorption spectrometric (AAS) method followed by the wastewater-based epidemiology (WBE) analysis. The mean concentrations of heavy metals in the wastewater samples were found to be in the following order (unit of mg/L): Fe > Ni > Zn > Cu > Cd (influent), and Fe > Ni > Zn > Cd > Cu (effluent). Among the metals, Fe concentrations were found to be the highest in effluent, with average values at 5.93 ± 5.319 mg/L, slightly over than a maximum permissible Fe concentration. Cadmium level in all STPs was significantly higher when compared to the maximum permissible Cd concentration (0.02 mg/L) allowed by Malaysia’s regulation, with an average of 0.13 ± 0.011 mg/L. Other metals concentration such as Cu, Ni and Zn in wastewater at the studied STPs showed low level and were considered safe. Using the WBE approach, the collected data were then calculated to estimate the population’s exposure consumption to heavy metals. Mass loading demonstrated high Fe exposure in all STPs but low Cd exposure, with the mean exposure of 1,924.86 ± 2451.772 and 46.91 ± 20.936 mg/1000p/d, respectively. Given the World Health Organization’s recommendation for tolerable weekly cadmium intake, the estimated human exposure to Cd in this study was particularly concerning, in addition to the lack of efficiency of Cd removal in the studied STPs. HIGHLIGHTS The order of the heavy metal mean concentrations in wastewater samples was Fe > Ni > Zn > Cu > Cd (influent), and Fe > Ni > Zn > Cd > Cu (effluent) The removal efficiency of the STPs followed the order: Cu > Fe > Zn > Cd > Ni The daily exposure rate of Fe was recorded as the highest exposure rate among other studied heavy metals (1924.7 ± 2451.772 mg/1000p/d) The daily exposure rate of Cd, estimated from the mass loads of total Cd, was found to be the lowest when compared to the other heavy metals (46.91 ± 20.936 mg/1000p/d) GRAPHICAL ABSTRACT

Spatiotemporal distribution and multi-source characteristics of microplastics in the soil and water environment of Poyang Lake Wetland, China

The increasing microplastics (MPs) pollution in freshwater wetlands has received global concerns. To investigate the spatiotemporal dynamics of MPs in the wetlands of Poyang Lake, surface water and sediment samples were collected from five rivers entering the lake as well as the confluence of Poyang Lake into the Yangtze River, in both dry and wet seasons. The MPs in water and sediment were extracted by the digestion-filtration method and flotation-separation-digestion-filtration method, respectively. Light microscope, Fourier transform infrared spectroscopy, and scanning electron microscope were used for microplastic characterization. The results showed that the abundance of MPs ranged from 32.1 to 127.3 n·L-1 in water samples, and from 533.3 to 1286.6 n·kg-1 in sediment samples during the wet season. In the dry season, the abundance of MPs ranged from 87.1 to 295.5 n·L-1 in water and from 460.0 to 1368.0 n·kg-1 in sediment. Compared with other freshwater wetlands, Poyang Lake had higher abundance of MPs. There were temporal and spatial differences among regions. The main forms of MPs included beads, fragment, film and fiber, and the corresponding polymer components were mainly polystyrene, polypropy-lene and polyethylene. Beads (35.7% in wet season and 52.0% in dry season) were the main form of MPs in water, while fragment (45.8% in wet season and 69.7% in dry season) was the main form of MPs in sediment. Small size (<0.1 mm) MPs were dominant (>50%) in water and sediment in both seasons. The abundance of MPs with different sizes decreased with the increases of size. The potential main sources of MPs in the wetlands of Poyang Lake included the discharge of industrial wastewater, discharge from urban and rural domestic sewage treatment plants, agricultural and fishing activities, and improper disposal of domestic wastes.

A Fixed-Film Bio-Media Process Used for Biological Nitrogen Removal from Sewage Treatment Plant

In this study, a lab-scale fixed-film bio-media process was developed and operated to evaluate nitrogen removal from domestic sewage treatment plants. For nitrogen removal, the fixed-film bio-media process was applied in series with anaerobic, anoxic, and aerobic units in three separate reactors that were operated continuously at the same loading rates and hydraulic retention time. A biofilm separation bioreactor was developed for on-site domestic wastewater treatment and the bioreactor employed synthetic fiber modules so that the biomass could be completely attached to the media. In this paper, the performance of the fixed-film bio-media process with an average flow rate was evaluated before and after stabilization of the treatment system for nitrogen removal. The results show that the fixed-film bio-media process was successful for improved nitrogen removal from secondary and tertiary treated wastewater, with a 77% decrease in the total nitrogen discharge. Rapid nitrification could be achieved, and denitrification was performed in the anoxic filter with external carbon supplements during tertiary treated sewage wastewater. However, aeration was supplied after the stabilization process to achieve the nitrification and denitrification reaction for nitrogen removal. However, stable aeration supply could enhance nitrification at moderate temperature with benefits from complete retention of nitrifying bacteria within the system due to bio-media separation.

ORGANIC REMOVAL IN DOMESTIC WASTEWATER USING ANAEROBIC TREATMENT SYSTEM-MBBR WITH FLOW RECIRCULATION RATIO AND INTERMITTENT AERATION

Aim: The modified Small-scale Domestic Sewage Treatment Plant (SDSTP) reactor with anaerobic fixed bed- aerobic Moving Bed Biofilm Reactor (MBBR) is implemented to find the optimum condition for organic degradation related to recirculation and intermittent aeration practices with the purpose to comply with the governmental regulation standard. Methodology and Results: This research have been done with the artificial wastewater with characteristic similar to the sewage treatment plant (STP) of Telkom company with ratio C:N:P of characterized domestic wastewater is 252.40:85.42:3.01 that consists of glucose, NH4Cl, potassium dihydrogen phosphate, potassium nitrate, and sodium nitrite (NaNO2). Reactor design related with attached biomass in media until 2478.56 mg MLVSS.L-1 with the growth kinetics rate (μ) of 0.4691 day—1. The artificial wastewater is applied the determine the optimum variation of flow recirculation and periodic aeration in specific Hydraulics Retention Time (HRT) and Organic Loading Rate (OLR). In this research, the optimum recirculation ratio for organic degradation is 26.40 L.h-1 and the optimum aeration frequency variation is 12 hours in intermittent frequency with the maximum efficiency of organic degradation of 76.10% with the degradation efficiency real domestic wastewater application from STP Telkom company is 83.09%. Conclusion, significance and impact study: Stover-Kincannon model is the best model with highest accuracy rate to model the degradation performance of organic compounds by the anaerobic fixed bed- aerobic MBBR SDSTP with determination coefficient 0.8623 and also degradation coefficient 38.121 day-1 compared with other models studied in this research.

Treatment and technology of domestic sewage for improvement of rural environment in China

It has been recorded that China’s rural environment threatened the lives of people due to the large amounts of wastewater treatment. The domestic sewage treatment plants were implemented in many parts of China to improve the environment of the country, and it has been noted that this sewage had a positive effect on the Chinese Rural Environment. Past studies recorded that China reached building sewage treatment plants with the capacity of 125 million m3. Moreover, most of these treatment plants employed Activated Sludge Process (ASP) along with the package treatments such as Anoxix-Oxic processes, Anaerobic processes, Oxidatin Ditch, and Sequencing Batch Reactors. Still there seems to be a gap in the effectiveness of wastewater treatment plants constructed with wastewater rising day-to-day. The main purpose of the current study is to review the rural wastewater treatments such as sewage systems and other treatment plants, which will improve the rural environment in China. This paper also highlights the characteristics of rural domestic sewage treatment. Furthermore, this paper also explores the applicability of rural sewage treatment technology in rural places of China. The challenges of the wastewater treatment in rural areas of China will also be closely monitored by the researcher.

Visible active clay based Sm2(WO4)3 nanocomposite for drug removal in pharmaceutical effluents

Antibacterial drug ofloxacin of fluoroquinolone family is identified in domestic sewage treatment plant, pharmaceutical and hospital effluents. Fluoroquinolones are toxic to the living organism and pollute the environment. Heterogeneous photocatalysis is found to be more efficient in degrading pharmaceutical compounds, and in particular clay-based photocatalysts are focused in recent research. Present study is oriented towards the preparation of a clay-based samarium tungstate Sm2(WO4)3 nanocomposite by hydrothermal-sonication process using locally obtained natural clay (NC). XRD, FT-IR, SEM, HRTEM, EDS, UV–Vis and PL spectroscopic techniques were used to characterize the properties of NCSm2(WO4)3. XRD data confirmed pristine monoclinic phase of Sm2(WO4)3 in NCSm2(WO4)3. The FT-IR of NCSm2(WO4)3 displayed the characteristic groups of Sm2(WO4)3 as well as that of natural clay. The band gap energies of Sm2(WO4)3, NCSm2(WO4)3 are 3.02 and 2.8 eV respectively. SEM images indicate the impregnation of Sm2(WO4)3 spherical particles on the surface of clay nanoflakes giving a heterostructure morphology. SAED pattern of HRTEM revealed the good crystalline nature of the nanocomposite. NCSm2(WO4)3 was able to degrade ofloxacin (OFX) and ibuprofen (IBP) almost completely in 80 min of visible light illumination. NCSm2(WO4)3 has excellent stability, and recyclability in drug degradation. Eight fold increase in BET surface area of NCSm2(WO4)3 relative to Sm2(WO4)3 and decrease in band gap energy make NCSm2(WO4)3 suitable for the industrial effluent treatment.

Impact of thermal pre-treatment on anaerobic co-digestion of sewage sludge and landfill leachate

The complex microbial flocs with rigid cell walls and undigested organic matter in the domestic sewage sludge defy anaerobic digestion, especially hydrolysis, the rate-limiting step of anaerobic digestion. The anaerobic digestion of municipal solid waste landfill leachate is challenging because of its high refractory organics and ammoniacal nitrogen. However, if sewage sludge and landfill leachate are mixed in an optimal ratio and pre-treated, they can be anaerobically co-digested and clean bioenergy can be harnessed. Among the pre-treatment methods, thermal pre-treatment is preferred because it is simple and economical yet effective. In this investigation, sewage sludge from a domestic sewage treatment plant and landfill leachate from an active municipal solid waste landfill were mixed in the ratio of 75:25 and thermally pre-treated at 70 °C for 60 min. The pre-treated substrates were anaerobically digested at 37 ± 1 °C using fresh cow dung slurry as the inocula. The results of this experiment were compared with the control experiment in which substrates without pre-treatment were used. Though biogas production from the fresh substrates was higher during the initial days, it decreased after the seventh day. For the thermal pre-treated substrates, the biogas production was low during the first week, which started to increase from the tenth day until the end of the experiment. The cumulative biogas yields from untreated and thermal pre-treated reactors were 723.5 and 418 mL, respectively.

Intermittent Microaeration Technology to Enhance the Carbon Source Release of Particulate Organic Matter in Domestic Sewage

Domestic sewage treatment plants often have insufficient carbon sources in the influent water. To solve this problem, the commonly used technical means include an additional carbon source, primary sludge fermentation, and excess sludge fermentation, but these methods are uneconomical, unsustainable, and not applicable to small-scale wastewater treatment plants. Intermittent microaeration technology has the advantages of low energy-consumption, ease of application, and low cost, and can effectively promote anaerobic digestion of municipal sludge; however little research has been reported on its use to enhance the carbon sources release of particulate organic matter (POM) from domestic wastewater. Therefore, the effect of intermittent microaeration on the carbon source release of POM was evaluated in this study, with POM as the control test. The results showed that the release concentration of soluble chemical oxygen demand (SCOD) was the highest on day 4 under microaerobic conditions, and the concentrations of SCOD, NH4+-N, and PO43−-P in the liquid phase were 1153, 137.1, and 13 mg/L, respectively. Compared with the control group, the SCOD concentration increased by 34.2%, and the NH4+-N and PO43−-P concentrations decreased by 18.65% and 17.09%, respectively. Intermittent microaeration can effectively promote the growth of Paludibacter, Actinomyces, and Trichococcus hydrolytic fermentation functional bacteria. Their relative abundances increased by 282.83%, 21.77%, and 23.47%, respectively, compared with the control group. It can simultaneously inhibit the growth of acetate-type methanogenic archaea, Methanosaeta and Methanosarcina, with a decrease in relative abundances of 16.81% and 6.63%, respectively. The aforementioned data show that intermittent microaeration can not only promote the hydrolysis of POM, but can also reduce the loss of acetic acid carbon source, which is a cost-effective technical way to enhance the release of a carbon source of particulate organic matter in domestic sewage.

Production of bioflocculant from Klebsiella pneumoniae: Evaluation of fish waste extract as substrate and flocculation performance

The bioflocculant producing bacterial strain – UKD24 was isolated from the domestic sewage treatment plant. The isolated strain was identified as Klebsiella pneumoniae by using 16S rRNA gene sequencing. The K. pneumoniae UKD24 showed remarkable flocculation rates when grown with the carbon sources namely glucose, sucrose and lactose, and many commercial nitrogen sources. Furthermore, the fish waste extract (FE) was used to enhance the productivity of the bioflocculant as a nitrogen supplement and it showed significant level of flocculation rate similar to the commercial nitrogen sources. The Box-Behnken experiments were designed to predict the optimal conditions for bioflocculant production and it suggested that glucose - 3.247 g L-1, FE - 0.5 g L-1 and inoculum size - 1% are the suitable levels for bioflocculant production. The FTIR analysis of the bioflocculant showed the functional groups related to the polysaccharides and the EEM analysis showed the fluorescence components related to the proteins and humic acids. The biochemical composition of the bioflocculant was identified as polysaccharides (24.36 ± 1.5%) and protein (12.15 ± 0.2%). The tested optimum conditions of the bioflocculant to induce flocculation were tested in the kaolin wastewater and it showed the optimum dosage of flocculant was 5 mg L-1 and the pH range was broad as 5 to 10. The cation dependency tests revealed that the monovalent and divalent cations are highly suitable for flocculation while the trivalent cations showed a moderate flocculation. The Cr(VI) removal efficiency of the bioflocculant showed that ∼35% of heavy metal is trapped into flocks during the flocculation.

METHANE PRODUCTION IN THE CO-DIGESTION OF LANDFILL LEACHATE WITH DOMESTIC SEWAGE AND THE METHANOGENIC ACTIVITY OF FULL-SCALE UASB REACTORS

The study aimed to individually assess the specific methanogenic activity of the sludge of 10 UASB reactors from a full-scale domestic sewage treatment plant (STP) and the sludge behavior under conditions of anaerobic co-digestion of leachate with domestic sewage in dilutions (v/v) of 0.1%, 1.0%, 2.5%, 5.0%, 10.0%, 25.0%, 50.0%, 75.0% and 100%. In order to compare the influence of the activity on co-digestion sludge, a parallel test was performed with sludge coming from the treatment of swine wastewater under the same conditions as the test with STP sludge. Specific methanogenic activity results showed the difference between STP sludge conversion capacities at each reactor, as well as preponderant conversion routes, which can have several origins within the mesh of factors that affect the units. Co-digestion analyses pointed out a better adaptation of piggery sludge to higher organic loads, such as the viability of up to 50% of leachate in relation to treated sewage volume, while the STP sludge showed a more delayed response in methane production. The best co-digestion condition was 10% leachate. The study highlights the possibility of increased leachate fractions in the co-digestion with domestic sewage with methane production potential, with incorporation of sludge from agro-industrial wastewater treatment.

Occurrence, source apportionment and source-specific risk assessment of antibiotics in a typical tributary of the Yellow River basin

The spatial distributions, sources, and source-specific risk apportionments of 26 antibiotics (5 categories) in the Fenhe River basin were determined based on sample data. The results showed that antibiotics were widely distributed in the surface water. There were significant differences between the different types of antibiotics, and the highest mean concentration was that of the sulfonamide category (33.74 ng/L), accounting for 36% of the total antibiotic concentration. Spatially, all antibiotics were mainly detected in the middle and downstream areas. The ecological risk assessment results showed that the significant risk rate of antibiotics accounted for 70% and was mainly distributed in the downstream area; however, the risks differed between the 5 categories. Quinolone antibiotics exhibited the highest significant risk rate, reaching 100%. The ecological risk associated with sulfamethoxazole was the highest among all detected antibiotics. The following five main factors influenced the antibiotic concentrations: aquaculture, pharmaceutical wastewater, livestock discharges, domestic sewage, and sewage treatment plants. Among these, pharmaceutical wastewater sources contributed the most (35%) to the total antibiotic concentration, and were distributed throughout the river. Although livestock discharges were not the main reason for the high level of ecological risk, these discharges were highest at certain sites in the midstream region. Different pollution sources posed different levels of ecological risk to the Fenhe River basin, the highest of which was pharmaceutical wastewater with a significant risk rate of 58%.