Phosphogypsum (PG), phosphate sludge (PS), and sewage sludge (SS) are regarded by-products produced in huge amounts. However, PG, PS and SS are no longer considered as waste, but as valued resources in accordance with the circular economy's rules. Their management provides a serious environmental problem. In order to assess the impacts of SS, PS, and PG on soil physico-chemical parameters (pH, EC, OM, nutrients, and heavy metals) in response to diverse experimental settings, the purpose of the current study was to conduct a meta-analysis on previously published results. The VOSviewer program was used to construct bibliometric maps using the VOS mapping and grouping techniques. The findings indicated that there were statistically significant changes (P < 0.05) in electrical conductivity (EC), organic matter (OM), and pH in connection to the different by-products employed. The application of SS considerably elevated pH by 46.15% compared to the control. Furthermore, a beneficial effect on P and K was detected, regardless of the by-product used. Moreover, Cd, Pb, and Ni concentrations in SS treatments had a substantial reduction of 30.46%, 30.70%, and 18.07%, respectively. Cd, Pb, and Cu concentrations in PG treatments revealed a substantial decrease of 47.71%, 36.14%, and 46.01%, respectively. Based on the acquired data, PG, PS, and SS need to be regularly monitored and regulated. This study serves as an early investigation for the construction of a new approach to restore damaged land on mine sites by employing phosphate industry by-products and sludge for revegetation objectives.

The discharge of fertilizers and untreated sewage from the Indian subcontinent was attributed to damage the coastal ecosystem and threat to the fishery resources. Based on the recent data collected along the Indian coasts, the issues were reanalyzed to identify potential mechanisms responsible. Carbon, nitrogen and oxygen isotopes revealed that the fertilizers used in the agricultural soil contaminate groundwaters, then fluxed to the coastal ocean. Similarly, the impact of municipal sewage is restricted close to the coast rather than spreading to the international waters. This reanalysis suggests that the occurrence of coastal eutrophication, hypoxia or shift in the ecosystem was mainly caused by natural processes such as coastal upwelling, stratification and reversing of coastal currents than hitherto hypothesized as the discharge of fertilizers and municipal sewage.

Introduction Floods are classified as one of the hydrological hazards affecting many countries worldwide. With most weather-related disasters occurring in developing countries, demographics and socioeconomic pattern changes have contributed to many losses relating to water-related disasters such as floods. South Africa is among the developing countries most frequently affected by natural disasters, particularly floods. Thus, this study assessed the causes and impact of floods on the communities of Bronville and Hani-park in Welkom in the Free State Province in South Africa.Methods The study adopted a quantitative approach, using a structured questionnaire to collect the data. The study used an R statistical package to analyze the data and applied descriptive statistics and a series of Generalized linear models to examine the impacts of floods in the community.Results The findings reveal a community-wide concern about flooding impacts. There was a statistically significant difference between whether floods affected your physical structure as an outcome variable and how the flooding affected participants (Wald chi 62 = 30.364; p = 0.001). Also, a significant difference was found regarding how floods affect the water quality in your community (Wald chi 2 = 1.496; p = 0.030). The subjective perception of flood impacts on households has been reported to be aligned with observed damage to physical structures, underscoring the direct influence of floods on various household elements. The study also emphasises the costly nature of flood recovery and the potential strain on household resources due to flooding. Respondents indicated floods adversely affect vegetation, soil stability, and ecological dynamics. he study also, reveals that while some residents affected by flooding reach out to their municipalities for support, many do not seek or receive financial assistance.Discussion The study concludes that floods have a considerable socioeconomic impact on households and communities, particularly regarding repair costs for flood-related damages. In addition, the study concludes that floods have significant implications for drinking water quality in the community, with statistical evidence supporting the claim that floods contribute to water quality degradation. The findings of flood preparedness suggest a clear gap in early warning dissemination and evacuation planning tailored to the study community's needs. The findings of this study underscore the urgent need for comprehensive and sustainable flood mitigation strategies in vulnerable communities like Bronville and Hani-park.

The large amount of sewage sludge ash (SSA) generated by incineration treatment of sewage sludge each year can seriously pollute the environment, and there is an urgent need to seek an effective resource utilization method for SSA treatment. SSA has the significant pozzolanic activity, and can be used as an auxiliary cementitious material. For that, SSA was adopted to modify lime soil in this work. The strength characteristics of SSA modified lime soil (SLS) were investigated by conducting unconfined compressive strength test and unconsolidated-undrained triaxial compression test, and X-ray diffraction (XRD) test and scanning electron microscopy (SEM) test were conducted to investigate the mineral composition, microstructure and porosity of SLS. It is observed that the unconfined compressive strength (UCS) increases first and then decreases with increasing SSA content in the range of 0-20 %, and reaches the maximum value while SSA content is 15 %, which increases by 25 % at the curing age of 28 days comparing to the specimen without SSA. Additionally, the triaxial strength and cohesive force both have the same change law as UCS with SSA increasing, and 15 % can be used as the optimal content of SSA to modify lime soil. The added SSA can promote the pozzolanic reaction, and more hydration products fill the specimen porosity so that the specimen strength can be improved. Furthermore, the porosity of SLS decreases first and then increases with SSA content increasing, and there is a linear relationship between the porosity and strength of SLS. Finally, a simple function is proposed, which can simulate the quantitative relationship between UCS and the triaxial strength with satisfying accuracy. Generally, the research results can be used as a reference for the application of SSA in soft soil foundation treatment.

Several methods have been used over time to improve the mechanical properties of fine-grained soils. One of the recently introduced materials for soil stabilization is incinerated sewage sludge ash (ISSA). This material is a by-product of the wastewater treatment process that is usually disposed of during the treatment cycle. This paper investigated the effects of adding the optimum amount of ISSA and a mixture of ISSA with hydrated lime (IL) on the mechanical properties of dispersive fine-grained soil. The effects of curing time on the UCS was also evaluated. The Mohr-Coulomb failure envelope parameters of the mixtures were subsequently estimated based on the performed test results using the Consoli et al (J Mater Civ Eng 27(5):04014174, 2015) method which eliminates the need to perform triaxial tests. The results indicated that ISSA and IL can improve the mechanical characteristics of the dispersive soil effectively and that curing time was substantial for better performance of the treated soil. Finally, the application of the Consoli and others method to predict the failure envelope parameters of the treated soil was evaluated using triaxial tests. The comparison of the results proved the suitability of the proposed method to estimate the failure envelope parameters of the ISSA and IL-treated dispersive soil.

The use of sewage sludge as a soil improver has been promoted in agroecosystems. However, sludges can contain toxic trace elements because of suboptimal wastewater treatment. Nonetheless, field studies investigating the negative effects of these practices on pollinators are lacking. We collected honeybees from an area where sewage sludge use is widespread, and one where it is precluded. Trace elements in soils and bees were quantified. Cadmium, chromium, lead, mercury, and nickel were investigated because they were the least correlated elements to each other and are known to be toxic. Their levels were related to oxidative stress and energy biomarkers, midgut epithelial health, body size and wing asymmetry of honeybees. We found increased carbohydrate content in sites with higher cadmium levels, increased histological damage to the midgut epithelium in the sewage sludge area, and the presence of dark spherites in the epithelium of bees collected from the sites with the highest lead levels. Finally, we found that honeybees with the highest lead content were smaller, and that wing fluctuating asymmetry increased in sites with increasing levels of mercury. To the best of our knowledge, this is the first comprehensive study of the concentration and effects on honeybees of trace elements potentially deriving from soil amendment practices.

Domestic sewage can greatly affect the macro-micro physical-mechanical properties of building foundation soils. In order to investigate the effect of domestic sewage on physical and mechanical properties of soils, the physicochemical properties of three groups of different concentrations of domestic sewage contaminated soil were tested through indoor experiments. Combined with scanning electron microscopy, X-ray diffraction experiments, and grey relational analysis, the degree of influence of different concentrations of domestic sewage on the physicochemical properties of soil was compared and analyzed from multiple perspectives such as microstructure and mineral composition, revealing the influencing mechanism of soil pollution by domestic sewage. The results showed that under the immersion of contaminated water, the color of the soaking water turned black first and then yellow, and brownish yellow secretions appeared on the surface of the soil samples. The moisture content, specific gravity, density, and pore ratio index of the soil samples immersed in 50% and 100% domestic sewage decreased with the increase of sewage concentration, while the liquid limit of the soil samples changed in the opposite direction. The immersion time had little effect on the slope of the compression curve of the soil samples soaked in tap water. For the soil samples immersed in domestic sewage, the slope of the compression curve and the compression coefficient increased with the increase of domestic sewage concentration and immersion time, while the compression modulus showed the opposite trend. In the soil samples immersed in tap water, there were a large number of small particles and cementitious substances, and the structure was relatively dense. With the increase of domestic sewage concentration, the microstructure of the soil changed significantly, with the appearance of sigle particle structure, loose and disorderly arrangement of particles, increased and enlarged pores, gradual reduction of small particle substances and cementitious substances, and the soil structure transformed from compact to loose. The research findings can provide theoretical reference for contaminated geotechnical engineering.

The majority of the studies on nanoscale zero-valent iron (nZVI) are conducted at a laboratory-scale, while fieldscale evidence is scarce. The objective of this study was to compare the metal(loid) immobilization efficiency of selected Fe -based materials under field conditions for a period of one year. Two contrasting metal(loid) (As, Cd, Pb, Zn) enriched soils from a smelter-contaminated area were amended with sulfidized nZVI (S-nZVI) solely or combined with thermally stabilized sewage sludge and compared to amendment with microscale iron grit. In the soil with higher pH (7.5) and organic matter content (TOC = 12.7 %), the application of amendments resulted in a moderate increase in pH and reduced As, Cd, Pb, and Zn leaching after 1-year, with S-nZVI and sludge combined being the most efficient, followed by iron grit and S-nZVI alone. However, the amendments had adverse impacts on microbial biomass quantity, S-nZVI being the least damaging. In the soil with a lower pH (6.0) and organic matter content (TOC = 2.3 %), the results were mixed; 0.01 M CaCl 2 extraction data showed only S-nZVI with sludge as remaining effective in reducing extractable concentrations of metals; on the other hand, Cd and Zn concentrations were increased in the extracted soil pore water solutions, in contrast to the two conventional amendments. Despite that, S-nZVI with sludge enhanced the quantity of microbial biomass in this soil. Additional earthworm avoidance data indicated that they generally avoided soil treated with all Fe -based materials, but the presence of sludge impacted their preferences somewhat. In summary, no significant differences between S-nZVI and iron grit were observed for metal(loid) immobilization, though sludge significantly improved the performance of S-nZVI in terms of soil health indicators. Therefore, this study indicates that S-nZVI amendment of soils alone should be avoided, though further field evidence from a broader range of soils is now required.

Groundwater pollution poses a significant threat globally, particularly in developing countries where inadequate sanitation facilities contribute to growing concerns about contamination from sewer leaks. Hence, the objective of this study is to present a comprehensive review, offering insights into diverse aspects of sewer leaks and their impacts on the urban groundwater system. This includes an exploration of leak sources, methods for leak detection, quantification approaches, analysis of contaminants in sewage along with their health effects, and strategies for mitigating both sewer leaks and groundwater contamination. This review addresses various factors leading to sewer infrastructure damage, emphasizing its importance in effective maintenance strategies. In this review, a range of contaminants released from sewer leaks were outlined, ranges from emerging contaminants to heavy metals that poses risk to the human health and environment. Further it evaluates various methods for detecting sewer leaks, emphasizing advancements in water quality analysis, visual, electromagnetic, and acoustics techniques. This research assesses diverse techniques for quantifying sewage leaks, including mass balance and wastewater balance and concludes pinpointing specific leak hotspots remains challenging. Furthermore, an appraisal of mitigation measures was also conducted, determining that rehabilitation serves as a more effective approach to stop leaks at their source. This paper delves into groundwater treatment methods, highlighting the difficulties in achieving optimal water quality and reveals that technologies such as Permeable Reactive Barrier and advanced oxidation processes exhibit potential in effectively removing trace-level pollutants. Overall, the review underscores the importance of understanding, detecting, and mitigating sewer leakage for the health and sustainability of groundwater systems.

With the expansion of urban areas, the amount of sludge produced by sewage treatment plants is increasing, raising big problems regarding the reintroduction of this sludge into nature in order to fully solve the wastewater problem. The application of sludge to agricultural surfaces or degraded land is a controversial solution since, despite the well-known benefits, sludge can, in certain cases, represent a real threat to both human health and the environment, with long-term harmful effects. The present study evaluates the potential genotoxicity of sludge using the Comet Test and three cellular bioindicators (lymphocytes, coelomocytes, and Allium cepa L.) for its quantification. To perform the tests, the soluble fraction of the sludge was used at concentrations of 25%, 50%, 75%, and 100%, as well as a negative control (H2O) and a positive control (H2O2). The Comet test indicated an increase in DNA damage among cells exposed for 4 h in the following order: coelomocytes, lymphocytes, and Allium cepa L. cells. Our results indicate that Allium cepa L. nuclei are more sensitive, with genotoxic effects being evident at concentrations as low as 25%. In coelomocytes, we recorded nuclear damage starting at a concentration of 75%. These results indicate the necessity of using multiple genotoxicity tests, combined in a test battery, to achieve a greater level of relevance. The concentration of the soluble fraction of the sludge has an inverse relationship with the auxin content in leaves and roots, suggesting varying levels of stress. The results of this study can contribute to the creation of a genotoxic profile of sewage sludge, facilitating decisions related to reducing its negative impact.