Distribution of Selected Dissolved and Particulate Heavy Metals in Lake Kenyir, Malaysia

This study was conducted to determine the concentration and possible sources of dissolved and particulate heavy metals in Lake Kenyir, Terengganu, Malaysia. The heavy metals studied included Cd, Fe, Pb, Zn and Cu. The findings indicated that the mean concentrations found in the dissolved form for surface waters were in decreasing order of Fe>Zn>Pb~Cu>Cd. A similar trend was also recorded for the particulate form i.e., Fe>Zn>Pb~Cu>Cd. In terms of vertical distribution, most of the heavy metals showed a trend of increasing concentrations from the surface to the bottom waters. The main sources of heavy metals were from anthropogenic activities such as discharge of untreated sewage, surface runoff and boat activity. However, the levels of dissolved heavy metals were still lower compared to other study areas in Malaysia. The dissolved heavy metal concentrations were equivalent with Class II based on the National Water Quality Standard for Malaysia.

Microbiological load evaluation of white shrimp (Nematopalaemon hastatus Aurivillius, 1898) in the coastal waters of Ondo state, Nigeria

This study investigated the condition factor with microbial load of Nematopalaemon hastatus (Aurivillius, 1898) collected for two years from four coastal towns in Ilaje communities of Ondo State, Nigeria. Shrimps’ weight, length and condition factor were determined using standard methods while estimation of microbial load (Total heterotrophic bacteria, coliform, Escherichia coli, Salmonella/Shigella, and fungal counts) was done using standard microbiological methods. The correlation between microbial load and condition factor was thereafter determined using regression analysis. N. hastatus exhibited allometric growth, with low but consistent condition factor. Mean heterotrophic bacteria count was 1.107×102 CFU/g and 1.079×102 CFU/g during the dry and wet season, respectively. Mean coliform count, total Salmonella-Shigella and E. coli counts were 0.398×102 CFU/g, 0.218×102 CFU/g and 0.303×102 CFU/g, respectively, during the wet season. A significant increase in counts (mean) was observed in the dry season for the coliform (0.404×102 CFU/g), total Salmonella-Shigella (0.234×102 CFU/g) and E. coli (0.326×102 CFU/g). The mean fungal count was 0.604×102 SFU/g and 0.563×102 SFU/g during the wet and dry seasons, respectively. The microbial loads were below acceptable limits; therefore, shrimps of the study area are safe for consumption. Conclusively, the condition factor of the shrimps was non-significantly influenced by the microbes. However, there is a need to regulate and/or prevent untreated sewage and effluent discharge into natural water bodies to reduce the environmental hazards it may portend and also obtain relatively safe aquatic products for consumption.

Health Risk Assessment, Pore Water Chemistry, and Assessment of Trace Metals Transfer from Two Untreated Sewage Sludge Types to Tomato Crop (Lycopersicon esculentum) at Different Application Levels

The application of untreated sewage sludge to cropland in water-deficient areas is common practice. A study was conducted to investigate the transfer of trace elements from sewage sludge to tomato crop and the potential health risk to humans. Two types of sewage sludge, ISS (I-9 Sector wastewater treatment plant, Islamabad) and WSS (Water and Sanitation Authority wastewater treatment plant, Faisalabad), were applied at 0.5%, 1.0%, and 1.5% w/w and compared with control (without any amendment). The test crop was tomato (Lycopersicon esculentum). Results revealed that the ECe of soil was increased by these treatments with respect to all application levels. The levels of Pb (lead) and Zn (Zinc) solubility in soil were increased about 46- and 28-fold by the application of ISS at 1.5% and 16- and 22-fold by the application of WSS at 1.5%, respectively. The highest shoot biomass was recorded with 0.5% level of WSS, while higher rates (1.0% and 1.5%) of both ISS and WSS showed significant (p < 0.001) decline in shoot biomass production, and the lowest SFW was recorded with the addition of ISS at 1.5% application rate (a significant reduction of 44%) compared to control. The pore water analysis and correlation depicted that dissolved organic carbon (DOC) controlled the release of Zn and Pb. The PLI (value < 1) indicated that the overall pollution of trace metals in the investigated samples was absent, but the Igeo and CF showed the contamination potential for Cd, Cu, and Ni was moderate to strong. DIM and HRI analysis suggested that the tomato was safe for human consumption. The HRI values for all trace metals were below the permissible limit (HRI = 1) described by USEPA-IRIS. It was concluded that a lower rate of both sewage sludge types produces more biomass and less accumulation of trace metals in the test crop.

Insight Into Impacts of Sewage Discharge and River Self-Purification on Microbial Dynamics and Pathogenicity in River Ecosystem

Sewage directly discharge causes serious environmental problems. Here, the effects of treated and untreated sewage on the river ecosystem were investigated. The variations of microbial community structure, including infectious pathogenic bacteria and functional bacteria related to nitrogen, phosphorus, and COD metabolism were studied in detail. Bacterial diversity and richness were significantly decreased, while, Proteobacteria containing various infectious pathogens, such as Vibrio and Helicobacter, significantly increased after the discharge of raw sewage. Although the microbial structure was slightly restored and the abundance of most pathogenic bacteria was also slightly reduced through river self-purification, direct discharge of raw sewage caused severe and short-term irreversible damage to the river environment. Direct discharge also introduced various pollutants such as nitrogen, phosphorus, and COD, increasing the corresponding functional bacteria and their related genes. Furthermore, the high abundance of pathogenic bacteria of the drain outlet was mainly from raw sewage rather than bacteria reproduction caused by water deterioration according to the RDA analysis. With these results, direct discharge disturbed the ecological balance of the river. Therefore, more attention is needed to provide a hygienic situation for people and all sewage should be treated properly. In conclusion, all sewage should be treated properly before discharge into ecosystems to mitigate its negative impacts on receiving water bodies.

Antibiotic Resistance and Sewage-Associated Marker Genes in Untreated Sewage and a River Characterized During Baseflow and Stormflow

Since sewage is a hotspot for antibiotic resistance genes (ARGs), the identification of ARGs in environmental waters impacted by sewage, and their correlation to fecal indicators, is necessary to implement management strategies. In this study, sewage treatment plant (STP) influent samples were collected and analyzed using quantitative polymerase chain reaction (qPCR) to investigate the abundance and correlations between sewage-associated markers (i.e., Bacteroides HF183, Lachnospiraceae Lachno3, crAssphage) and ARGs indicating resistance to nine antibiotics (belonging to aminoglycosides, beta-lactams, sulfonamides, macrolides, and tetracyclines). All ARGs, except blaVIM, and sewage-associated marker genes were always detected in untreated sewage, and ermF and sul1 were detected in the greatest abundances. intl1 was also highly abundant in untreated sewage samples. Significant correlations were identified between sewage-associated marker genes, ARGs and the intl1 in untreated sewage (τ = 0.488, p = 0.0125). Of the three sewage-associated marker genes, the BIO-ENV procedure identified that HF183 alone best maximized correlations to ARGs and intl1 (τ = 0.590). Additionally, grab samples were collected from peri-urban and urban sites along the Brisbane River system during base and stormflow conditions, and analyzed for Escherichia coli, ARGs, the intl1, and sewage-associated marker genes using quantitative polymerase chain reaction (qPCR). Significant correlations were identified between E. coli, ARGs, and intl1 (τ = 0.0893, p = 0.0032), as well as with sewage-associated marker genes in water samples from the Brisbane River system (τ = 0.3229, p = 0.0001). Of the sewage-associated marker genes and E. coli, the BIO-ENV procedure identified that crAssphage alone maximized correlations with ARGs and intl1 in river samples (τ = 0.4148). Significant differences in E. coli, ARGs, intl1, and sewage-associated marker genes, and by flow condition (i.e., base vs. storm), and site types (peri-urban vs. urban) combined were identified (R = 0.3668, p = 0.0001), where percent dissimilarities between the multi-factorial groups ranged between 20.8 and 11.2%. Results from this study suggest increased levels of certain ARGs and sewage-associated marker genes in stormflow river water samples compared to base flow conditions. E. coli, HF183 and crAssphage may serve as potential indicators of sewage-derived ARGs under stormflow conditions, and this merits further investigation. Data presented in this study will be valuable to water quality managers to understand the links between sewage pollution and ARGs in urban environments.

Plant debris are hotbeds for pathogenic bacteria on recreational sandy beaches

On recreational sandy beaches, there are guidelines for the management of bacterial pollution in coastal waters regarding untreated sewage, urban wastewater, and industrial wastewater. However, terrestrial plant debris on coastal beaches can be abundant especially after floods and whilst it has rarely been considered a concern, the bacterial population associated with this type of pollution from the viewpoint of public health has not been adequately assessed. In this study, microbes associated with plant debris drifting onto Kizaki Beach in Japan were monitored for 8 months throughout the rainy season, summer, typhoon season, and winter. Here we show that faecal-indicator bacteria in the plant debris and sand under the debris were significantly higher than the number of faecal bacteria in the sand after a 2015 typhoon. When we focused on specific pathogenic bacteria, Brevundimonas vesicularis and Pseudomonas alcaligenes were commonly detected only in the plant debris and sand under the debris during the survey period. The prompt removal of plant debris would therefore help create safer beaches.

Author Correction: Detection of untreated sewage discharges to watercourses using machine learning

A Correction to this paper has been published: https://doi.org/10.1038/s41545-021-00116-3