Characterization and utilization of water treatment sludge for coagulation of raw water.

One of the critical steps in the treatment of raw water for human consumption is clarification. It encompasses coagulation and flocculation to reduce the concentration of suspended solids in turn producing a semi-solid slurry called water treatment sludge (WTS). It is necessary to characterize and find economic and sustainable ways to utilize the WTS. The WTS used in this work was characterized and contained aluminum (Al) (20.3% Al2O3) and iron (Fe) (5.28% Fe2O3) making it suitable for the development of a coagulant. A less energy-intensive way, through atmospheric acid leaching of WTS, was developed to extract Al and Fe for use as a coagulant. The sulphuric acid concentration and solid loading that gave the highest Al concentration were determined to be 3N and 5 g/100 mL, respectively. Turbidity reduction achieved with the developed coagulant ranged from 91 to 99% and was higher than that obtained in related studies due to the higher concentrations of Al and Fe in the WTS used in this study. Since the coagulant was very acidic, it was co-dosed with calcium oxide at 10 g/L of water to adjust the pH of the final water to allowable pH values for potable water (6.5-9.5).

Challenges of plastic waste generation and management in sub-Saharan Africa: A review.

Recently, the issues of land-based plastics and their associated challenges in the marine world have been widely publicised in the media and scientific literature. Thus far, despite these communications, there have been few reports that have focused on the issues that acute plastic waste generation and its poor management pose to human health and the global environment. Also, articles on ways to mitigate these issues particularly in sub-Saharan Africa have not been documented. Indeed, there is significant scope for improvements in plastic waste management in developing countries, which offer a wide range of economic and environmental benefits. Plastic waste generation in sub-Saharan Africa is dependent on many factors like urbanization, etc. Currently, the population of sub-Saharan Africa is around 1 billion as of the year 2019, the amount of generated waste is 180 million tonnes at the rate of 0.5% per capita per day, the amount that is openly dumped is 70% and the plastic waste generated annually is 17 million tonnes. Therefore, this study aims to provide an overview of the plastic lifecycle and problems associated with plastic waste management in sub-Saharan Africa, including current practices, public participation and opinion, and government regulations. In addition, this highlight aims to outline the impact of plastic waste proliferation on man and the environment; and the economic and environmental benefits of proper plastic waste management. Critical discussion of current processes and the suitability of potential solutions provide the basis for proposition on mitigation measures to avert the negative impact of plastic waste.

Extraction and precipitation of phosphorus from sewage sludge.

Raw sewage sludge from East Rand Water Care Association (ERWAT) had high phosphorus (P) content, approximately 15.2% (w/w) P2O5, which indicates a potential resource for the limiting nutrient. Leaching sewage sludge with 1M sulphuric acid at 5% solid loading for 2h resulted in an 82% phosphorus extraction. However, the phosphorus was recovered as iron phosphates, thus a further purification step using ion exchange to remove iron was required to increase the degree of P release. Magnesium oxide and ammonium hydroxide were used as magnesium and nitrogen sources, respectively, as well as pH regulators to precipitate P as struvite. 57% struvite was precipitated and the total phosphorus content of the precipitate was 25.9%. Kinetic studies showed that the leaching of phosphorus follows the Dickinson model for the first 100min with a rate of reaction of about 2×10-5s-1. The rate limiting step is controlled by diffusion. Phosphorus solubility in 2% critic acid was almost 96%, which is the amount of phosphorus available to plants if the precipitate is applied as a fertiliser. Environmental, gram-positive Bacillus subtilis were found in the precipitate, which are harmless to the environment since they already exist in the soil where the precipitate can be applied as a fertiliser.

Designing of sampling programmes for industrial effluent monitoring.

INTRODUCTION: Monitoring of effluent discharges from industrial establishments discharging directly into municipality sewers is one of the major water pollution control activities conducted by municipalities. For largely industrialised municipalities, the task can be quite expensive and not effective if sampling programmes are not properly designed. In most cases, samples are randomly collected without proper knowledge of the discharge patterns of various industries. As a result, the information obtained does not give a good reflection of the quality of effluent being discharged. METHODS: These problems can be resolved by adapting a statistical approach to the design of sampling programmes. This approach is useful in determining the frequency of sampling, the number of samples needed to estimate the average concentration of target pollution indicator parameters and the magnitude of the uncertainty involved. RESULTS: The benefits and applications of this approach are demonstrated by a case study presented in this paper. It was found that the number of samples and cost of sample analysis can be greatly reduced by the use of systematic instead of random sampling. CONCLUSION: The statistical approach greatly improves the estimate of monthly means of pollution indicator parameters and is an effective approach for pollution control when coupled with the "polluter pays principle".