Physicochemical characterization and heavy metals analysis from industrial discharges in Upper Awash River Basin, Ethiopia

Bitew K Dessie; Bezaye Tessema; Endaweke Asegide; Degefie Tibebe; Tena Alamirew; Claire L Walsh; Gete Zeleke

doi:10.1016/j.toxrep.2022.06.002

Physicochemical characterization and heavy metals analysis from industrial discharges in Upper Awash River Basin, Ethiopia

Toxicol Rep. 2022 Jun 8:9:1297-1307. doi: 10.1016/j.toxrep.2022.06.002. eCollection 2022.

Authors

Bitew K Dessie^{1

2}, Bezaye Tessema^{1

3}, Endaweke Asegide^{1

4

5}, Degefie Tibebe¹, Tena Alamirew^{1

4}, Claire L Walsh⁶, Gete Zeleke¹

Affiliations

¹ Water and Land Resource Centre of Addis Ababa University, Addis Ababa, Ethiopia.
² College of Natural and Computational Sciences, University of Gondar, P.O.Box 196, Gondar, Ethiopia.
³ ARUA Water CoE, Institute for Water Research, Rhodes University, South Africa.
⁴ Ethiopian Institute of Water Resources, Addis Ababa University, Ethiopia.
⁵ Adama Science and Technology University, School of Architecture and Engineering, Ethiopia.
⁶ School of Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.

Abstract

The recent expansion of industries in Addis Ababa is causing additional environmental pollution through wastewater discharges; this is becoming a critical concern. Addis Ababa is located in the upper Awash River basin, and is the main source of industrial pollutants to the river. In this study, physicochemical parameters, nutrients and heavy metal content of wastewaters released from 16 factories, 6 tanneries, 6 beverages and 4 diverse factories, and the Akaki-Kality central wastewater treatment plant in Addis Ababa, were sampled to assess the level of pollutants. Heavy metals were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). Analysis of nutrients were conducted using Palintest Photometer. Physicochemical characteristics were measured either in situ using a portable micro meter or in the laboratory. Among the measured physicochemical properties, critical issues were observed with electrical conductivity, total dissolved solids and total hardness. Effluents from all of the tanneries, and a number of other factories, were found at levels higher than the maximum limits of various guideline standards. In addition, samples from two of the tanneries (T1 and T5), two beverage factories (B3 and B6) and the central wastewater treatment plant showed elevated concentrations of PO₄ ^3-, which violated the limit (10 mg/l) set by Environmental Protection Agency of Ethiopia (ETHEPA). The two tanneries (T1 and T5) also contained higher SO₄ ^2- than the guideline limit of 1000 mg/l. On the other hand, only one factory, one brewery (B3), exhibited NO₃ ^- above the standard limit of 20 mg/l. Whereas NH₃, NH₄ ⁺, Cl^-, S^2- and NO₂ ^- were within the limits in all of the samples. Severe pollution was found in wastewaters from tanneries, where half of them (T1, T5 and T6) contained Cr beyond the maximum limit of 2000 µg/l. Furthermore, a third of the tanneries (T1 and T5) and a beverage factory (B5) contained Fe, Mn, Zn and Cu, higher than the ETHEPA limits of 10000, 5000, 5000 and 2000 µg/l, respectively. Waste disposal from factories without proper treatment can cause great harm to the local people and the environment. Hence, the results of this study call for regulatory bodies to pay close attention to factories, particularly tanneries, in Addis Ababa in implementing adequate treatments of their wastewater discharges.

Keywords: Addis Ababa; Effluents; Heavy metals; ICP-OES; Nutrients; Photometer 7500.