Sewage Effluent Research Articles

DISSEMINATION OF DIARRHEAGENIC BACTERIA IN COMMUNITY-BASED NATURAL WATER SOURCES AND WASTEWATER ENVIRONMENTS: A COMPREHENSIVE ANALYSIS IN UNIVERSITY OF NIGERIA, NSUKKA AND ITS METROPOLIS.

The presence of pathogenic strains abounds in our environment, arising from many sources. The study was aimed at identifying Vibrio species, E. coli, and other coliforms in various water sources within a university setting and its metropolis. Approximately 20 samples from roof-collected rainwater, municipal piped tap water, borehole water and 60 samples of sewage effluent from the central effluent water of University of Nigeria, Nsukka were systematically collected at intervals and subjected to bacteriological analysis. The samples underwent dilutions, and aliquots were inoculated on chromocult and thiosulfate-citrate-bile salts-sucrose (TCBS) agar. Simultaneously, 100 ml of each natural water sample underwent membrane filtration, followed by the inoculation of TCBS agar plates in duplicates. Both sets of culture plates were incubated at 37 °C for 24 h. Further biochemical characterization was performed after microscopy. Susceptibility profile was done using disk diffusion assay. Descriptive statistics were used in the aggregation of the results where necessary. Results revealed that each sample, when plated on chromocult agar, yielded a substantial number of colonies of E. coli (bluish colour) and other coliforms (pink-red colonies). Notably, wastewater gave a maximum yield of Vibrio cholera. Conversely, all significant pathogenic Vibrio species were recovered on TCBS agar inoculated with natural water samples, wastewater and sewage effluent, with isolation rates appearing independent of both time (in weeks) and collection points. Antimicrobial susceptibility studies disclosed that some of the isolates exhibited antibiotic resistance. The study underscores the need to install appropriate measures to mitigate the contamination of the environment. Keywords: Wastewater, Vibrio, Antimicrobial, Chromocult, Pathogen, Sewage

Spatiotemporal distributions and ecological risk of polycyclic aromatic hydrocarbons in the surface seawater of Laizhou Bay, China.

The spatial-temporal distribution, source, and potential ecological risk of polycyclic aromatic hydrocarbons (PAHs) in surface seawater from Laizhou Bay were investigated. The total PAH (ΣPAH) concentrations ranged from 277 to 4393 ng/L with an average of 1178 ng/L, thereby suggesting a relatively moderate to high PAH exposure level in Laizhou Bay in comparison to other bays in the world. The composition patterns and source apportionment results revealed that the coal, biomass burning, diesel emissions, and petroleum combustion as well as the combination of these processes were the dominant sources of PAHs in the surface water, which were closely associated with sail process and sewage effluents. The ecological risk assessment indicated that benzo(a)pyrene (BaP), phenanthrene (Phe), luoranthene (Flua), and naphthalene (Nap) would exist ecological risks in most of surface seawater sites, but the probabilistic risk assessment (PRA) results showed that the current level of risk is not as severe as the risk quotient (RQ) results revealed.

Campylobacter Species: New Insight, Clinical Diagnosis and Laboratory Approach

Campylobacter, a prevalent cause of global gastroenteritis, has exhibited an escalating impact worldwide, affecting both industrialized and developing nations. Even though Campylobacter jejuni and C. coli are the main causes of infection, new pathogens make it imperative to comprehend the disease mechanisms, dynamics of transmission, and evolution of less-studied species. Accessible whole-genome sequences obtained through high-throughput sequencing have made it easier to conduct in-depth pathogenomic studies, particularly on species such as C. fetus and C. concisus. These studies have shown novel applications in clinical microbiology by revealing genomic traits associated with pathogenicity and offering insights into the evolutionary mechanisms shaping their genomes. Effective pathogen management urgently requires deeper understanding of the evolution of pathogenicity in emerging Campylobacter species are urgently required for effective pathogen management. This comprehensive review synthesizes existing knowledge and outlines future research directions in this crucial field. The Gram-negative, non-spore-forming, curved or spiral rods known as campylobacters include a "thermophilic group" that is important to the water industry and includes C. jejuni, C. coli, and C. upsaliensis. Acute diarrhea is the usual symptom of a human Campylobacter infection, and key virulence factors have been identified as antibiotic resistance genes and flagellar DNA. Many campylobacters are frequently found in sewage and treated sewage effluents, whereas surface waters are less contaminated. Testing for Campylobacter prevalence through epidemiological methods requires a careful balance between phenotypic and genotypic data. Campylobacters are sensitive to oxygen, but they have strong survival strategies that may involve the formation of biofilms. Methods of inactivation that work well for coliforms are thought to be appropriate for Campylobacter. In addition to providing a synthesis of current knowledge and identifying future research directions to advance strategies for the effective management and mitigation of Campylobacter-related infections, this thorough review highlights the urgent need for additional research to deepen our understanding of these pathogens. The investigation of genetic features linked to pathogenicity, dynamics of transmission, and survival strategies highlights the complex character of Campylobacter infections. The dynamic nature of Campylobacter as a primary cause of gastroenteritis necessitates continued research endeavors to guide focused interventions and lessen the worldwide impact of this grave public health issue.

Photocatalytic Degradation of Pharmaceutical Residues from Water and Sewage Effluent Using Different TiO2 Nanomaterials.

Pharmaceuticals are widely used and often discharged without metabolism into the aquatic systems. The photocatalytic degradation of pharmaceutical compounds propranolol, mebeverine, and carbamazepine was studied using different titanium dioxide nanostructures suspended in water under UV and UV-visible irradiation. Among three different photocatalysts, the degradation was most effective by using Degussa P25 TiO2, followed by Hombikat UV100 and Aldrich TiO2. The photocatalytic performance was dependent on photocatalyst dosage, with an optimum concentration of 150 mg L-1. The natural aquatic colloids were shown to enhance the extent of photocatalysis, and the effect was correlated with their aromatic carbon content. In addition, the photocatalysis of pharmaceuticals was enhanced by the presence of nitrate, but inhibited by the presence of 2-propanol, indicating the importance of hydroxyl radicals. Under optimum conditions, the pharmaceuticals were rapidly degraded, with a half-life of 1.9 min, 2.1 min, and 3.2 min for propranolol, mebeverine, and carbamazepine, respectively. In treating sewage effluent samples, the photocatalytic rate constants for propranolol (0.28 min-1), mebeverine (0.21 min-1), and carbamazepine (0.15 min-1) were similar to those in water samples, demonstrating the potential of photocatalysis as a clean technology for the effective removal of pharmaceuticals from sewage effluent.

A Study on Analysis of Water Quality of Two Rivers Ganges and Yamuna

Water is very essential for life existence. About 71% of earth’s surface is occupied by water making it a blue planet. The 97% of the ocean water can’t be used as it has high salt concentration, some is frozen in glaciers/ polar ice caps. Even the distribution of water on earth is uneven at some places there is flood and others drought. Human activities have interfered in the natural renewal of groundwater resulting in water shortage and availability for consumption. The degradable and nonbiodegradable wastes which are discharged openly in water bodies pose severe threat to aquatic life. The article presents a study on on quarterly changes in water parameters including temperature, transparency, dissolved oxygen, pH, free carbon dioxide, alkalinity, conductance, total dissolved solids, hardness, chloride, nitrate, phosphate, dissolved organic matter, BOD in the water of river Ganges and Yamuna. The results showed rising trend in the levels of these parameters over the years. The results show increase in levels of CO2 , hardness, total dissolved solid, pH and BOD during the months of April to September. The levels of nitrate and phosphate were detected in trace amounts. The chloride level of Yamuna was high as compared to that of Ganges. The drop in alkalinity during monsoon months may be due to increased dilution and disappearance of CO2 . The studies made in water of river Ganges and Yamuna has shown that the river is under severe threat of pollution due to the discharge of untreated or semi treated sewage and industrial effluents.

Understanding the risks of antibiotics released from livestock on agricultural productivity: Evidence from mung bean [Vigna radiata (L.) Wilczek] pot experiment

Antibiotics of veterinary origin are generally released to agricultural fields via grazing animals or manure. Antibiotics can also be delivered to agricultural lands by reclaimed wastewater irrigation as they have been found in both raw and processed sewage effluents. Possible effects of antibiotics on crop plants, particularly of mung bean (Vigna radiata cv. NM-11) were investigated in the present study. A pot experiment comprising four different treatments (0, 1 µg L-1, 5 µg L-1, and 10 µg L-1) of amoxicillin was carried out under natural atmospheric conditions. Five applications each of 200 mL of different concentrations of amoxicillin and one concentration of distilled water (control) were administered at two leaf stage onwards to the respective groups of mung bean plants. The effects of amoxicillin were assessed on the post-germination traits (agronomic parameters) of mung bean during ontogenesis and at the time of full development. The antibiotic adversely affected the plant agronomic traits which were determined twice at four-week intervals. The amoxicillin, even in small concentrations, adversely affected the growth as well as yield parameters of mung bean plants. Moreover, varying concentrations of amoxicillin used in the experiment also declined chlorophyll biosynthesis especially at the later stages of plant development.

“Gray Carbon” in Sewage Treatment Plants: A Neglected Carbon Sink

This study introduces the concept of “gray carbon,” emphasizing its critical role in carbon sequestration in sewage treatment. By focusing on recalcitrant dissolved organic carbon (RDOC) in sewage effluents and its subsequent transformation in marine environments, we underscore the significant impact of sewage-derived organic carbon on the efficiency of carbon sequestration. Through analysis of carboxylic-rich alicyclic molecules, this study illuminates the convergence in the molecular compositions of RDOC across various aquatic systems. Dark-culture experiments reveal marked variations in the microbial community structures of the aforementioned molecules, indicating that these changes may play an important role in the degradation and subsequent transformation of organic matter in marine environments. These insights lay the groundwork for advancing technologies designed to enhance wastewater alkalinity, which will improve the sustainability of wastewater treatment and preserve marine ecosystems. Enhancing sewage alkalinity can influence microbial processes and chemical equilibria, potentially affecting the formation and accumulation of gray carbon. Further investigation is necessary to understand the potential effect of alkalinity enhancement on the microbial communities and biochemical pathways involved in gray carbon formation. Our findings support the integration of gray carbon strategies into broader carbon neutrality initiatives, providing a scientific and technological blueprint for enhancing global carbon management and mitigating climate change.

Physiochemical Characteristics Analysis of Garrah River Water at Shahjahanpur, Ganga River Basin, Uttar Pradesh, India

This study focuses on the physiochemical analysis of the Garrah River in Shahjahanpur, within the Ganga River Basin, Uttar Pradesh, India. The research evaluates the impact of various pollutants, including industrial and municipal sewage, on the river's water quality. Water samples were collected from three locations along the river, representing different pollution levels. The analysis included parameters such as pH, dissolved oxygen (DO), total suspended solids (TSS), color, odor, electrical conductivity, temperature, chemical oxygen demand (COD), salinity, and the concentrations of various elements. The findings showed variations in water quality parameters, with DO, TSS, COD, and heavy metals indicating significant pollution, particularly downstream. Color and odor also suggested pollution from nearby industries. The study revealed that some parameters exceeded WHO standards for drinking water, raising concerns about health risks from exposure to contaminants like chromium. Urgent actions are required to treat municipal sewage and industrial effluents before discharging into the Garrah River. This research highlights the need for ongoing monitoring and sustainable management of water resources in the Ganga River Basin to protect the ecosystem and local communities. It underscores the importance of improving water quality in the region.

ESTRESSE TOXICOLÓGICO EM UM RIO ALTAMENTE IMPACTADO NO AMBIENTE PORTUÁRIO DE SANTOS, SP

TOXICOLOGICAL STRESS IN A HIGHLY IMPACTED RIVER FROM THE PORT ENVIRONMENT OF SANTOS, SP. There are many stilts and industry, which discharge sewage, domestic garbage and industrial effluents in the Pouca Saúde River from the port environment of Santos, São Paulo (SP) State. However, ecotoxicological studies in this river are rare. In this study, we seek to fill this gap by analyzing physicochemical, toxicological, and chemical conditions. Surface water and sediment samples were collected at 2 sampling sites with riparian community activities and industrial activities in the summer, autumn, winter and spring. The parameters analyzed were pH, alkalinity, turbidity, salinity, oils, greases, dissolved oxygen (DO), toxicological and cytotoxicity with mitotic index (MI) of onion roots using Allium cepa roots, and concentration of Pb, Zn, Hg, Ni and Cd. Our results showed alterations in the DO, turbidity, oils/greases and reduction of MI when compared to the respective control. Ni and Zn in sediment samples presented concentrations exceeding levels occasionally associated with adverse biological effects “threshold effect level”. These results suggested that the water quality of the Pouca Saúde River is influenced by both presences of heavy metals contamination and the seasons, i.e. by the tide. Thus, the toxic potential monitoring carried out in this study is of paramount importance to this river.

Carotenoids from wastewater-grown microalgae biomass: Life cycle assessment and techno-economical analysis

Microalgae stand out as a valuable source of carotenoids, with potential applications in various industrial sectors. Cultivating microalgae in wastewater emerges as an alternative to mitigate the high costs associated with the synthetic production of these compounds while contributing to sanitation resource recovery. Previous studies demonstrated the potential for obtaining lutein and betacarotene from biomass cultivated in domestic sewage and agro-industrial effluent. This study conducted comprehensive economic and life cycle analyses to evaluate cultivation reactors (high-rate pond and hybrid system) and extraction methods (ethyl acetate solvent and supercritical fluid) to acquire 1 kg of carotenoids efficiently. For all evaluated scenarios, higher environmental impacts were observed in the Human carcinogenic toxicity category and human health environmental damage associated with ethyl acetate and electricity consumption. Ethyl acetate also stood out with higher costs. The high-rate pond and hybrid system showed similar environmental impacts in scenarios with ethyl acetate extraction; however, when supercritical fluid was used, cultivation in the first reactor resulted in 2.2–6.2 times lower environmental impacts in Midpoint categories. Regarding the extraction method, the use of supercritical fluid demonstrated superior economic and environmental performance despite registering a 53% higher energy consumption than solvent extraction. Thus, for the viability of obtaining carotenoids from microalgae biomass, we recommend that two-stage cultivation approaches, incorporating solvent recovery steps and biomass valorization in a cascade manner within a biorefinery context, be considered in future studies.

Monitoramento ambiental da qualidade dos sedimentos e do status dos vestígios de metais em um rio tropical perene no sul da Índia: uma exploração usando análise multivariada

Abstract: Aim The Kallada River is exposed to several kinds of pollution from domestic, civic, recreational, and agricultural activities and human settlements. The objectives of the study were to assess sediment quality, especially the trace metal concentration and to compare with the previous reports on the sources of pollutants in the Kallada River. Methods A total of 12 sediment variables including the following metals: iron (Fe), manganese (Mn), chromium (Cr), and zinc (Zn) were analyzed. Atomic Absorption Spectrophotometer (AAS) was used to detect trace metal concentration in the sediment samples. Statistical tools such as Pearson’s correlation, Principal component analysis (PCA), and Cluster analysis (CA) were employed to analyze the data and source of pollutants. Results This investigation indicated that Fe was the most accumulated element in the sediments, and the midstream (K6 and K10) and downstream sites (K11 to K15) showed a much higher concentration level than the upstream sites. The concentrations of trace metals in sediment samples followed the order Fe> Mn> Cu>Zn. Conclusions The present study concluded that major sources of pollutants were sewage and civic effluents and agricultural discharges. These may cause a severe threat to the Kallada River and health risk to the local populations, which rely on the river, primarily for drinking purposes. Hence, appropriate conservation policies to reduce pollution are therefore essential.

From the experience of utilization of sewage heat in Hostel

This research paper explores the feasibility of utilizing heat from sewage effluent to heat the drying room in student hostel No. 2 of the State Energy Institute of Turkmenistan. Temperature measurements revealed that sewage water typically ranges around 29.5 °C. While initial measurements indicated that drainage from the washing machine, reaching 36.5 °C, held limited potential for space heating due to low overall thermal capacity, the authors investigated the possibility of reusing this thermal energy. The study found that preheating water in a heat exchanger using the washing machine discharge (36.5 °C) resulted in a reduction of 0.065 kWh of electrical energy consumption over a 60-minute operation.

Successful Water Quality Improvement Practices of a Campus’s River in Ningbo Based on Water Replenishment and Circulation Since Year 2017

Rivers play a critical role in regional water quality, but from time to time concentration of surface water pollutants can easily exceed both national and local water standards. This study debates the feasibility and effectiveness of utilizing the natural treatment potential of flowing river water by replenishing treated sewage effluent and forced circulating. The research combines field experiments and laboratory analyses to assess the impact of this approach on water quality. Theoretical simulation with one-dimension modeling recommended by China’s national standard of “Code of Practice for Computation on Allowable Permitted Assimilative Capacity of Water Bodies” (GB/T 25173-2010) indicates that the target campus river water’s cycle flowing contributes to the further removal of key pollutants from treated sewage, resulting in the improvement of campus river’s water quality downstream along its forced circulation. NH3-N and CODMn levels of the campus’s river water were notably reduced and met the planning water qualities as expected.

Развитие методики расчёта нормативов допустимого сброса жидких производственных отходов с учётом региональных особенностей водных объектов

The problem of regulating the discharge of liquid wastes into water bodies is the most urgent task and is carried out on the basis of establishing standards of permissible discharge (SPD). Many authors note that the key problem of setting the SPD is the use of maximum allowable concentrations (MAC) as threshold values, determined without taking into account regional peculiarities of formation of natural water composition and its ability to dilute wastewater. We have proposed the development of the methodology for calculating SPD, based on the condition that ensuring the disposal of liquid wastes at the level of permissible discharge standards will not lead to a change in the water quality class determined using the specific combinatorial index of water pollution (SCIWP). In the previous publication we have substantiated territorial threshold concentrations (TTC) based on the analysis of long-term data sets of hydrochemical observations, which allow us to take into account regional features of the geochemical background of water bodies, including the content of substances of dual genesis. They also implicitly allow taking into account hydrological and hydrochemical factors that ensure the ability of natural waters to dilute liquid waste effluents. The obtained TTCs are proposed to be used for calculation of permissible concentrations of substances in wastewater instead of MAC. SPD is established by cyclic iteration of TTC values by 10%, with parallel calculation of SCIWP, until the index is transferred to another water quality class. This paper presents the results of approbation of the proposed development of the methodology of SPD calculation for liquid waste from Оpen JSC “Kazan Synthetic Rubber Plant” discharged into the Volga River. The obtained calculation results make more stringent requirements to the value of SPD for substances mainly of anthropogenic origin. For some substances of dual genesis, the value of SPD was higher, which allows us to make more adequate requirements to water users for treatment of sewage effluents.

Antibiotic resistance determinants among carbapenemase producing bacteria isolated from wastewaters of Kathmandu, Nepal

The emergence of carbapenem resistant bacteria (CRB) possesses a remarkable threat to the health of humans. CRB and carbapenem resistance genes (CRGs) have frequently been reported in clinical isolates from hospitals, however, their occurrence and distribution in wastewaters from various sources and river water have not been emphasized in Nepal. So, this study aimed to detect carbapenem resistant bacterial isolates and their resistance determinants in river water and different types of wastewaters. River water and both untreated and treated wastewater samples from hospitals, pharmaceutical industries, and municipal sewage were collected in summer and winter seasons. From 68 grab wastewater samples, CRB were detected only in 16 samples, which included eight hospital wastewater, and four each from untreated municipal sewage and river water. A total of 25 CRB isolates were detected with dominance of E. coli (44.0%) and K. pneumoniae (24.0%). The majority of the isolates harbored blaNDM-1 (76.0%), followed by blaOXA (36.0%) and blaKPC (20.0%) genes. Hospital wastewater majorly contributed to the presence of blaNDM-1, blaKPC, and blaOXA along with intI1 genes compared to river water and untreated municipal sewage, especially during the winter season. However, CRB were not detected in treated effluents of hospitals and municipal sewage, and both influents and effluents from pharmaceutical industries. The combined presence of each blaNDM-1 &blaOXA and blaKPC &blaOXA occurred in 16.0% of the bacterial isolates. The increased minimum inhibitory concentration (MIC) of meropenem was significantly associated with the presence of CRGs. The results of this study highlight the significance of carbapenem resistance in bacteria isolated from wastewater and river water, and underscore the necessity for efficient monitoring and control strategies to prevent the dispersion of carbapenem resistance in the environment and its potential consequences on human health.

Assessment of untreated wastewater pollution and heavy metal contamination in the Euphrates river

ABSTRACT This study investigates the impact of untreated wastewater on a section of the Euphrates River in Al-Diwaniyah, Iraq. The unregulated discharge of sewage and industrial effluents has caused severe pollution in this area. The research measures electrical conductivity, turbidity, total dissolved solids, dissolved oxygen, total hardness, biological oxygen demand and heavy metals (Ni, Cr, Pb, Co, Cd, Cu, Fe) using Inductively Coupled Plasma Atomic Emission Spectrometry. Approximately 40 water sampling stations were selected for analysis and the Heavy Metal Pollution Index (HPI) was used to assess water quality. The study employed Inverse Distance Weighting (IDW) tool, to predict HPI values and their spatial distribution. The accuracy of prediction maps was evaluated using regression analysis by comparing observed values with predicted values from the maps. The study emphasizes the excessive pollution levels in the Euphrates River, specifically exceeding Iraqi standard thresholds for Ni, Fe, and Cd concentrations.

Seasonal variations of microplastic in sediment, Chironomus sp. larvae, and chironomid tubes in two wastewater sites in Sohag Governorate, Egypt

Microplastic (MP) contamination is an acknowledged global problem that poses a severe risk to aquatic ecosystem biota. Nevertheless, little is known about their prevalence in animal construction. The main objective of our study was to reduce the gap information of seasonal abundance, distribution, composition, and risk assessment of MP contamination. The concentrations of MPs in sediment, Chironomus sp. larvae, and their tubes were found to be higher in site 2 (S2) than in site 1 (S1) during the four seasons of the year. However, MP concentrations ranged from 312 ± 64.7 to 470 ± 70 items/kg dry weight, 0.79 ± 0.16 to 1.1 ± 0.3 particles/individual, and 0.5 ± 0.04 to 0.9 ± 0.04 particles/tube in sediment, Chironomus, and chironomid tubes, respectively. Blue and red polyester fibers are the most dominant MPs which are distributed in sediment, Chironomus, and chironomid tubes. The length of the dominant fiber accumulates in Chironomus, and their tubes are highly varied compared to that of the substrate. Additionally, we found that the mean number of MPs/individual larvae in the fourth instar was significantly higher than that in the second instar. Risk indicators for the environment, polymer risk assessment, and pollution load were estimated, where they were higher in S2 than in S1 correlated to MPs abundance and polymer type. The seasonal fluctuation in MP concentration, characterization, and risk in the two sites could depend on the amount of sewage effluent discharged into the wastewater treatment plants (WWTPs), which was reflected by Chironomus sp. larvae. Therefore, further research should be done to adopt the applicability of Chironomus as MP bioindicators in various freshwater environments throughout the world.

Returnable MoS2@carbon nitride nanotube composite hollow spheres drive photo-self-Fenton-PMS system for synergistic catalytic and photocatalytic tetracycline degradation

In this work, we synthesized hollow sphere composites of MoS2@carbon nitride nanotube (MoS2@TCN-S) for in-situ formation of H2O2 under visible light. The photo-self-Fenton system was further coupled with peroxymonosulfate (P-SF-PMS) for promoted reactive oxygen species generation and tetracycline degradation, so that the P-SF-PMS(MoS2@TCN-S) system can remove 94.3 % TC within 120 min, and the removal efficiencies after 15 cycles decrease by less than 5 %. The P-SF-PMS(MoS2@TCN-S) system also shows excellent degradation performance for actual wastewater, with COD removal rates of domestic sewage and secondary sedimentation tank effluent reaching 64.6 % and 58.7 % within 120 min. Quenching experiment and ESR results reveal the synergy of PMS and P-SF system, which was the key to improving the degradability and pH (3–9) adaptability of the P-SF-PMS system. Under alkaline conditions, PMS and H2O2 generated on MoS2@TCN-S activate each other and form 1O2 and OH, which solves the problem of poor degradation of P-SF system under alkaline conditions. Under acidic and neutral conditions, O2– becomes the main ROS, the activation of PMS by O2– and the synergistic effect of PMS and H2O2 make the P-SF-PMS system get rid of the dependence on H+. In addition, direct Z-scheme heterojunction enables MoS2@TCN-S to exhibit faster electron transfer ability, faster H2O2 generation ability, stronger adsorption capacity for PMS, and lower activation barrier for *HSO5, which also enhances the synergistic effect between PMS and P-SF system. In this study, a new type of multi-functional water purification material is proposed, and the synergism of PMS and P-SF system is revealed.

Evaluation of Organic Matter Contribution Using Absorbance and Chromatographic Parameters in Lake Paldang, Republic of Korea

Organic matter in lakes is categorized into allochthonous organic matter, such as leaves and sewage effluent, and autochthonous organic matter, generated by microorganisms within the water system. In this study, organic matter composition was analyzed using UV-vis spectroscopy and liquid chromatography-organic carbon detection (LC-OCD). Several allochthonous natural organic matter substances were collected including leaves, green leaves, forest soils, and paddy soils. The organic matter composition analysis in our study sites revealed that humic substances comprised the highest proportion (36.5–42.3%). Also, individual samples at each site exhibited distinct characteristics. This study used a humic substance-diagram (HS-diagram) and principal component analysis (PCA) to trace the sources affecting the river water quality and identify their origins. The humic substances of soil origin predominantly influenced the water quality, with the impact of organic matter significantly pronounced during the July rainfall period. Compared with the PCA results, the contribution of the humic substance (HS, 48.9%) and building block (BB, 42.0%) indices appeared higher between June and July in summer, likely due to non-degradable substances released by heavy rain. In fall, the contribution of low molecular weight neutrals increased from 71.2% to 85.2%, owing to a humic substance influx and decomposition. This study demonstrated the application of estimating the relative contributions of source materials in lakes utilized for drinking and agricultural water to identify sources, aiding in the development of efficient watershed management plans.

Multifaceted benefits of magnesium hydroxide dosing in sewer systems: Impacts on downstream wastewater treatment processes

Magnesium hydroxide [Mg(OH)2] is a non-hazardous chemical widely applied in sewer systems for managing odour and corrosion. Despite its proven effectiveness in mitigating these issues, the impacts of dosing Mg(OH)2 in sewers on downstream wastewater treatment plants have not been comprehensively investigated. Through a one-year operation of laboratory-scale urban wastewater systems, including sewer reactors, sequencing batch reactors, and anaerobic sludge digesters, the findings indicated that Mg(OH)2 dosing in sewer systems had multifaceted benefits on downstream treatment processes. Compared to the control, the Mg(OH)2-dosed experimental system displayed elevated sewage pH (8.8±0.1vs 7.1±0.1), reduced sulfide concentration by 35.1%±4.9% (6.7±0.9mgSL−1), and lower methane concentration by 58.0%±4.9% (19.1±3.6mgCODL−1). Additionally, it increased alkalinity by 16.3%±2.2% (51.9±5.4mgCaCO3L−1), and volatile fatty acids concentration by 207.4%±22.2% (56.6±9.0mgCODL−1) in sewer effluent. While these changes offered limited advantages for downstream nitrogen removal in systems with sufficient alkalinity and carbon sources, significant improvements in ammonium oxidation rate and NOx reduction rate were observed in cases with limited alkalinity and carbon sources availability. Moreover, Mg(OH)2 dosing in upstream did not have any detrimental effects on anaerobic sludge digesters. Magnesium-phosphate precipitation led to a 31.7%±4.1% reduction in phosphate concertation in anaerobic digester sludge supernatant (56.1±10.4mgPL−1). The retention of magnesium in sludge increased settleability by 13.9%±1.6% and improved digested sludge dewaterability by 10.7%±5.3%. Consequently, the use of Mg(OH)2 dosing in sewers could potentially reduce downstream chemical demand and costs for carbon sources (e.g., acetate), pH adjustment and sludge dewatering.