Although access to clean and potable water is a requirement for healthy living, the constant release of non-point source pollutants into water bodies has resulted in water quality degradation. In a bid to curb this situation, water quality models are used as a tool. This study reviews 10 non-point source models, namely: AGNPS, ANSWERS, CREAMS, SWRRB, HSPF, SWAT, EPD RIV1, DMA, CMBA, and MA, giving consideration to their nature, components, area of use, strengths, and limitations. Our review indicated that hydrological processes and mechanisms involved in the movement of non-point source pollutants have not been completely developed in these models. However, HSPF and EPD RIV1 models (which have in-stream process components) are limited due to limitations in their operations and computational difficulties. Further research would seek to develop a non-point source pollutant model that would not only adequately and effectively simulate non-point source pollutants in water bodies, but would also be easy to assess, user-friendly, and time-efficient.

In recent years, the use of antibiotics for human medicine, animal husbandry, agriculture, aquaculture, and product preservation has become a common practice. The use and application of antibiotics leave significant residues in different forms, with the aquatic environment becoming the critical sink for accumulating antibiotic residues. Numerous studies have been conducted to understand antibiotic removal and persistence in the aquatic environment. Nevertheless, there is still a huge knowledge gap on their complex interactions in the natural environment, their removal mechanism, and the monitoring of their fate in the environment. Water quality models are practical tools for simulating the fate and transport of pollutant mass in the aquatic environment. This paper reports an overview of the physical, chemical, and biological elimination mechanisms responsible for the degradation of antibiotics in natural surface water systems. It provides an in-depth review of commonly used quantitative fate models. An effort has been made to provide a compressive review of the modeling philosophy, mathematical nature, environmental applicability, parameter estimation, prediction efficiency, strength, and limitation of commonly used environmental antibiotic fate models. The study provides information linking paradigms of elimination kinetics and their simulation in the antibiotic fate models aiming at critical issues regarding current model development and future perspectives and to help users select appropriate models for practical water quality assessment and management.

Studies in recent years have shown that most reactive pollutants in natural rivers originate from non-point sources such as agricultural lands and informal settlements through rainfall runoff. Much work has centred on simulating decaying substances in rivers from point-source discharges. To expand on the area of non-point source modelling in rivers, a non-point source hybrid cells in series model for simulation of reactive pollutants in rivers is proposed. The potential of the proposed model has been demonstrated and found to simulate decay from non-point sources in streams and rivers satisfactorily. The proposed model is compared with the numerical solution of the ADE model with added components for non-point source and first-order reaction kinetic. The comparisons indicate reasonably good agreement. The breakthrough curves obtained from the proposed model shows its capability to simulate reactive pollutant transport in natural rivers effectively.

Owode, a sprawling water catchment area better known for its commercial activities in metal and iron casting and fabrication, is located off the Lagos Lagoon and the Ajuwon River, in Lagos State. The extensive iron and steel work along with seasonal flooding of the area and the habits of the people in this area is considered a threat to its groundwater integrity. Samples designated SW1, SW2, and SW3 for stream water WW1, WW2, and WW3 for well water and BH1, BH2, and BH3 for samples collected from boreholes were collected and analyzed to determine the presence of certain physicochemical elements and heavy metals. Including pH, EC, TDS, DO, SO42-, Cl, NO3-, and PO43-. Heavy metals analyzed include Fe, Pb, Zn, Cu, Cr, Cd, and Mn. The findings showed that while a number of parameters when compared with the WHO and NADWQ stipulated maximum acceptable concentration fell within acceptable limits, others especially the heavy metals had trace elevations above the maximum acceptable levels which if not checked could have serious future groundwater contamination implications.

Power generation is becoming an increasing problem in South Africa. South Africa produces approximately 90% of its electricity from coal-fired power stations and only 5% from hydroelectric power stations and pumped storage. Durban has a very steep topography, which results in high pressure in certain parts of the water distribution network (WDN). Leakage is costly and contributes to a large extent to non-revenue water (NRW) in the network. Pressure reducing valves (PRVs) are used in WDNs to control the pressure in the pipework to reduce leakage. This excess pressure can be used to generate electricity by a pump acting as a turbine (PAT). The electricity generated is a function of the flow rate and the pressure reduction through the PAT. The hydraulic modelling software EPANET 2.2 is used for the analysis of the Cornubia Integrated Human Settlement Development Phase 2A WDN in Durban. EPANET is used to determine the strategic placement of PATs in the WDN and their setting and configuration to extract the most energy and reduce pressure in the system. A configuration of five PATs of different sizes extracts a total power output of 166.31 kW and reduces leakage in the WDN by 45.59 kL per month, which is an 18.16% reduction in leakage.