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

Raymond S Malikula,Petra Chiipa,Fabiano G D Thulu,Harold W T Mapoma,Chikumbusko C Kaonga

doi:10.3390/w14010121

Abstract

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.

Highlights

Wastes generated from industries, homes, marketplaces, and any other areas need to be treated to avoid polluting the environment
This is in line with the main objective of the study, which is about heavy metal and nutrient loads for samples from a wastewater treatment facility and the associated risks
This study assessed heavy metal and microbiological and physicochemical parameters in samples from Manase and Soche Wastewater Treatment Plants (WWTPs) in Blantyre, Malawi. pH range in effluent for both WWTPs was within the WHO and Malawi standard acceptable limits, and it was higher in dry season as compared to rainy season in both WWTPs

Summary

Introduction

Wastes generated from industries, homes, marketplaces, and any other areas need to be treated to avoid polluting the environment. According to Kalulu et al [1], many developing countries lack the infrastructure for waste treatment. In some instances, this is due to lack of land caused by high population growth. Other countries struggle to treat wastes in their existing centralized wastewater treatment systems due to dysfunctional equipment and inadequate treatment capacity. This leads to an appropriate-to-partial treatment, which later affects the water bodies they are discharged in [2]. The Government of Malawi established dumping sites, such as landfills and wastewater treatment facilities, to combat these problems. In Blantyre, there are three main WWTPs, namely Soche, Limbe, and Manase (Blantyre) [3]

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Conclusion