Daily variation of heavy metal contamination and its potential sources along the major urban wastewater channel in Kampala, Uganda

Abstract

Heavy metal pollution from untreated industrial wastewater has become a major concern to the environment and public health in many rapidly growing cities in low-income countries. Previous studies on heavy metals of urban wastewater systems have focused on long-term (weekly or seasonal) variations, while only few studies investigated short-term (daily) variation to capture potential bulk discharges. To monitor and enforce wastewater discharge regulations and reduce industrial pollution, a better understanding of the short-term variation of these pollutants and industrial discharge practices is needed. The aim of this study is to assess the daily variation of heavy metals and physicochemical parameters along the major urban wastewater system in Kampala, Uganda. Over 1 week, daily water samples were collected at 16 locations and analyzed for lead (Pb), mercury (Hg), copper (Cu), and chromium (Cr) and a range of physicochemical parameters. Additionally, 25 key informant interviews with industries were administered to investigate their potential to contaminate the environment. Among 78 water samples, 29 exceeded the national standards for Pb (> 0.1 mg/L) and one for Hg (> 0.01 mg/L). High daily variation and peak concentrations were detected which are likely due to industries retaining their effluents and discharging them irregularly. Although 24 industries used heavy metals in their manufacturing processes and are likely to discharge heavy metals, only ten industries had a wastewater treatment system in place. Our results show that repeated measurements of heavy metals over short time intervals are needed to capture their high daily variation in an urban wastewater system. Furthermore, there is an urgent need to register industries and to assess their effluent composition in order to select appropriate wastewater management measures.

Seasonal Variation of Water quality and Heavy Metal Pollution Index of 5 Ponds of Raipur City, India

“…Second, the sewage management system needs to be improved at the city level along with the industrial waste (Dietler et al, 2019). Much research proposed to manage the storm and sewage water by adding to the ponds.…”

Spatial Distribution Characteristics and Sources of Nutrients and Heavy Metals in the Xiujiang River of Poyang Lake Basin in the Dry Season

“…A cluster analysis method was adopted in this study, and the sampling points were divided into CA1, CA2, CA3, and CA4 Groups. These groups were composed of sampling points (4,32,33,34,35); (5,6,7,8,11,16,18,24,25,27,28,31,36,37,38); (9,12,13,14,15,19,20,21,22,23,29); and (1,2,3,10,17,26,30), respectively, as detailed in Figure 3. Table 3 shows that, with the exception of the T, pH, TP, and Zn, there were significant differences in the heavy metals and nutrients among the different groups.…”

“…Previous research results have shown that agricultural activities are the main sources of suspended solids and inorganic nutrients (phosphate and nitrate) in rivers, and agricultural fertilization is also considered the main source of heavy metals [4][5][6]. In addition, industrial wastewater contains a variety of heavy metals [7][8][9], and municipal discharges will also have significant impacts on the nutrient elements and heavy metal content in rivers [10][11][12]. Nutrients and heavy metals pollution in rivers will not only lead to the loss of biodiversity and environmental degradation, but also pose a serious threat to human health.…”

Removal of heavy metals from an industrial effluent by synthesized zeolite: Case of Bounoura industrial zone

“…Heavy metals are among the most abundant pollutants in liquid industrial effluents; these compounds have high potential of toxicity and are highly dangerous to ecosystems and human health. Most of these heavy metals are present in polluted waters including Hg, Pb, Ag, Cu, Cd, Cr, Zn, Ni, Co and Mn (Bhuiyan et al, 2011), and it has been found that many heavy metal ions produce strong health problems and damage plants and animals (Nahar et al, 2018;Dietler et al, 2019).The dangers of pollution of some heavy metals may be acute due to their severe toxicity even at low concentrations (Christensen et al, 2000;Jarup, 2003).…”