The study was conducted at a wastewater treatment plant (WWTP) in the North West Province of South Africa (SA), to investigate the effect of seasonal variations of rainfall and temperature on the fate of Escherichia coli (E. coli) and on chemical parameters. Both seasons showed variations in terms of rainfall levels and temperature. The average temperatures measured at the final effluent were 14 and 22°C for the dry and wet season, while the rainfall averages ranged between 0.0 and 69.0 mm and 16.0 and 258.9 mm for the dry and wet season, respectively. The impact of rainfall within the two seasons presented a variation in the plant inflow rate of 34 000 and 48 000 m³ during the dry and wet season, respectively. Higher E. coli concentrations were detected before and after chlorination in the wet season (1.86 x 10(5) and 8.40 x 10¹ MPN/100 mL) than in the dry season (2.26 x 10(4) and 5.10 x 10¹ MPN/100 mL). The recorded values for the chemical parameters in the dry and wet season were within the following ranges: ammonia (0.27 and 3.68 mg/L), chemical oxygen demand (COD) (29.53 and 22.10 mg/L), nitrate (9.21 and 2.40 mg/L) and ortho-phosphate (0.46 and 0.39 mg/L). Though the detections of these indicator parameters were affected differently by the seasonal variations, it is important to note that the efficiency of the WWTP in reducing these indicator parameters proved to be consistent across all seasons, except in the case of ammonia and nitrate. The majority of the studied parameters showed effective compliance when measured against SA regulatory standards (general limits) in both the dry and wet season, with the exception of ammonia during the wet season.

Spent coffee grounds were transformed into biochar using a hydrothermal method. Some of the biochar product was pre-treated through surfactant impregnation with sodium dodecyl sulphate (SDS) to enhance its adsorption capacity. The non-treated(NT) and pre-treated(PT) biochars were characterized using FTIR spectroscopy and SEM-EDS analyses, which revealed that the products had the potential for adsorption of heavy metals from solution and confirmed the successful impregnation of biochar with SDS surfactant. The two adsorbents were then used for the removal of cadmium from solution and the adsorption behavior and capacity determined through adsorption isotherm, kinetic, and thermodynamic studies. It was found that the cadmium was adsorbed in several concentric layers on the surface of the adsorbents through a chemisorption mechanism. The PT biochar was identified as a superior adsorbent, with a capacity of q e= 10.67 mg/g compared to the NT biochar with q e= 4.82 mg/g. The adsorption of cadmium onto the PT biochar was further determined to be spontaneous and endothermic. It was therefore concluded that the PT biochar shows potential as an adsorbent and could be considered for implementation in the treatment of metal-polluted effluents.

Abstract Two bacteria, namely Bacillus subtilis and Pseudomonas aeruginosa were exposed to different concentrations of diesel to increase their adaptation to the fossil fuel, and were used for the degradation of diesel-biodiesel blends. The biodegradation rate was evaluated using the redox indicator 2,6-dichlorophenol indophenol (DCPIP) test and gravimetric analysis. The preliminary exposure of cells to diesel proved to improve their biodegradation capacities, and exposure to a higher concentration (70%) of diesel resulted in maximum biodegradation of up to 58.38 g and 1.78 g of degraded oil per CFU/mL (1010) for P. aeruginosa and B. subtilis respectively. It was found that the adapted cells preferably used diesel in the blend. P. aeruginosa and B. subtilis exhibited different adaptation capabilities and biodegradation behaviour. Biodiesel stimulated the biodegradation of the diesel-biodiesel blends by non-adapted cells only; the adapted cells exhibited a different behaviour.

Cyanobacteria are potent producers of cyanotoxins that may present a health risk to people. This is especially important in rural areas where people use untreated surface water, containing cyanobacteria, for household purposes including cooking and drinking. Water is collected from these sources mainly in plastic containers, transported home and stored during use. This study investigated the occurrence of cyanobacteria and their associated toxins in these containers as well as in the associated surface water sources. The results suggest that cyanobacteria are transferred from the water sources to the containers and then survive and possibly grow in biofilm forming inside the vessels. Their associated cyanotoxins were not found in any health-significant quantities in containers. However, the occurrence of cyanobacteria in the water used by the households collected in containers clearly indicates that it can be an important route of exposure especially if toxic cyanobacteria are present in the source water. In several cases a risk of cyano-intoxication might exist unless the households undertake preventative measures.