Application of Process Intensification in the Treatment of Pit Latrine Sludge from Informal Settlements in Blantyre City, Malawi

Process intensification approaches in wastewater and sludge treatment for the removal of pollutants

Process Intensification (PI) is the modification or integration of conventional or novel processes within a single unit operation in order to improve product quality and reduce waste. PI offers numerous advantages, including a reduction in the initial and operational costs, an improvement in product quality/quantity, the generation of less waste, and an increase in process safety. The synergistic effect of PI in comparison to the conventional procedure ensures maximizing resource efficiency. PI can be accomplished in two ways: either by integrating various processes or by modifying the design of equipment to improve operational efficiency. In this regard, the present review provides a comprehensive insight into the application of PI in wastewater and sludge treatment methods and discusses the operational advantages. This review provides a comprehensive list of different PI approaches applied in wastewater and sludge treatment to remove pollutants and the various equipment, techniques and reactors used in PI. The second section addresses the challenges of PI in wastewater treatment that removes dyes, pesticides, organic and inorganic pollutants, micro- and nano-plastics, persistent organic pollutants, pharmaceutical and personal care pollutants.

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

Heavy metals may cause acute and chronic toxic effects to humans and other organisms, hence the need to treat wastewater properly, as it contains these toxicants. This work aimed at assessing zinc, copper, cadmium, and chromium in water, soil, and plants that are irrigated with effluent from Manase and Soche Wastewater Treatment Plants (WWTPs) in Blantyre, Malawi. Atomic Absorption Spectrophotometry (AAS) was used to assess the heavy metals. Heavy Metal Health Risk Assessment (HMHRA) on plants (vegetables) around both WWTPs was also conducted. Average daily dose (ADD) and target hazard quotients (THQ) were used to assess HMHRA. Physicochemical parameters were determined using standard methods from American Public Health Association (APHA). The heavy metal ranges were below detection limit (BDL) to 6.94 mg/L in water, 0.0003 to 4.48 mg/kg in soil, and 3 to 32 mg/L in plants. The results revealed that plants irrigated with effluent from WWTP had high values of aforementioned metals exceeding the Malawi Standards and WHO permissible limits. Furthermore, the health risk assessment values showed that vegetables consumed for a long period of time from Manase WWTP were likely to cause adverse health effects as compared to those from Soche WWTP.