Heavy Metals and Nutrients Loads in Water, Soil, and Crops Irrigated with Effluent from WWTPs in Blantyre City, Malawi

Environmental surveillance for Salmonella Typhi in rivers and wastewater from an informal sewage network in Blantyre, Malawi

Environmental surveillance for Salmonella Typhi may provide information on the community-level dynamics of typhoid fever in resource poor regions experiencing high disease burden. Many knowledge gaps concerning the feasibility of ES remain, especially in areas lacking formal sewage systems. We implemented protocols for S. Typhi ES, including site selection and catchment population estimation, sample concentration and testing using qPCR for S. Typhi specific gene targets. Between May 2021 and May 2022, we collected grab samples and Moore swabs from 43 sites in Blantyre, Malawi. Catchment characteristics, water quality, and human faecal contamination (qPCR for Bacteroides HF183) were also recorded. Their association with S. Typhi detection was investigated using a logistic mixed-effects regression analysis. Prevalence of S. Typhi in ES samples was 2.1% (1.1-4.0%) and 3.9% (1.9-7.9%) for grab and Moore swab samples, respectively. HF183 was associated S. Typhi positivity, with a unit increase in log genome copies/microlitre increasing the odds of detection of S. Typhi by 1.56 (95% CI: 1.29-1.89) and 1.33 (1.10-1.61) in Moore swabs and grab samples, respectively. The location and timing of S. Typhi detection through ES was not associated with the incidence of typhoid fever reported in associated catchment populations. During this period of relatively low typhoid fever incidence, wastewater surveillance continued to detect S. Typhi in human sewage and wastewater suggesting that ES using natural river systems can be a sensitive indicator of transmission.

Valorisation of hydrothermal liquefaction wastewater in agriculture: effects on tobacco plants and rhizosphere microbiota

Industrial wastewater obtained from hydrothermal liquefaction (HTL-WW) of food wastes for biofuels production could represent a source of crop nutrients since it is characterized by a high amount of organic and inorganic compounds. In the present work, the potential use of HTL-WW as irrigation water for industrial crops was investigated. The composition of the HTL-WW was rich in nitrogen, phosphorus, and potassium with high level of organic carbon. A pot experiment with Nicotiana tabacum L. plants was conducted using diluted wastewater to reduce the concentration of some chemical elements below the official accepted threshold values. Plants were grown in the greenhouse under controlled conditions for 21 days and irrigated with diluted HTL-WW every 24 hours. Soils and plants were sampled every seven days to evaluate, over time, the effect of wastewater irrigation both on soil microbial populations, through high-throughput sequencing, and plant growth parameters, through the measurement of different biometric indices. Metagenomic results highlighted that, in the HTL-WW treated rhizosphere, the microbial populations shifted via their mechanisms of adaptation to the new environmental conditions, establishing a new balance among bacterial and fungal communities. Identification of microbial taxa occurring in the rhizosphere of tobacco plants during the experiment highlighted that the HTL-WW application improved the growth of Micrococcaceae, Nocardiaceae and Nectriaceae, which included key species for denitrification, organic compounds degradation and plant growth promotion. As a result, irrigation with HTL-WW improved the overall performance of tobacco plants which showed higher leaf greenness and increased number of flowers compared to irrigated control plants. Overall, these results demonstrate the potential feasibility of using of HTL-WW in irrigated agriculture.

Factors Affecting Water Quality and the Structure of Zooplankton Communities in Wastewater Reservoirs of the Right-Bank Sorbulak Canal System (South-Eastern Kazakhstan)

This work aims to assess the main factors that determined the variability of environmental and biological variables in wastewater reservoirs of the Right-Bank Sorbulak Canal system (South-Eastern Kazakhstan). We used standard methods for the collection and analysis of data, as well as the principal components analysis (PCA) to assess the relationship between environmental and biological indicators. The average depth of the surveyed reservoirs was 4.1–10.0 m, temperature—21.7–25.7 °C, pH—9.41–10.00, permanganate index—16.22–19.07 mgO/dm3, N-NO2—0.03–0.13, N-NO3—1.28–3.00, N-NH4—0.30–0.53, PO4—0.14–0.39, Si—3.69–8.26, Mn—0.03–0.07, Fe—0.34–0.38 mg/dm3. The content of Cd, Co, Pb, Zn, and Cr was low, Cu—0.012–0.036 mg/dm3. The water quality is influenced by the wastewater composition, chemical interactions, morphometric and physical-chemical conditions of the reservoir, pollution of the coastal area, and secondary water pollution. Changes in the species composition and zooplankton abundance reflected the instability of external conditions. PCA showed the priority influence of carbonates, bicarbonates, magnesium, temperature, nutrients, and heavy metals on zooplankton structure. The results obtained demonstrate the indicator significance of zooplankton, and the methodological approaches can be used to assess water bodies with the complex pollution located in other regions.