Aloe steudneri gel as natural flocculant for textile wastewater treatment

Amare Tiruneh Adugna*and Nahom Mankir Gebresilasie

Department of Environmental Engineering, College of Biological and Chemical Engineering, Addis Ababa Science and

Technology University, P.O. Box 16417, Addis Ababa, Ethiopia

*Corresponding author. E-mail: amardugna@yahoo.com; amaretiru@gmail.com

Abstract

This study focused on the evaluation of Aloe steudneri gel for textile wastewater clarification with identification of major phytochemical groups and physicochemical characteristics of Aloe steudneri. Optimization of pH, flocculant dose, mixing speed and time were studied for Aloe steudneri gel and synthetic polyacrylamide. A jar test was used to perform the flocculation at optimum conditions (pH 7.3, flocculant dose 33 ml, mixing time 20 minutes and speed 61 rpm). Phytochemical groups like tannins, flavonoids and saponins were identified and the gel showed a good result of 1.9 g H2O/dry polymer for swelling capacity and 6.2 g oil/weight for fat adsorption capacity. At the optimum conditions, the turbidity removal was 92.3% for Aloe steudneri gel and 92.7% for polyacrylamide. Moreover, the removal efficiencies for chemical oxygen demand, 5-day biological oxygen demand, total suspended solids and lead were 76.8%, 83.5%, 57.9% and 77% for Aloe steudneri gel and 78%, 89%, 51% and 72% for polyacrylamide, respectively. Therefore, it is possible to conclude that Aloe steudneri gel can substitute the polyacrylamide as there are no significant differences in their removal efficiencies.

INTRODUCTION

Water is a crucial component of life, its uses range from drinking and hygiene to industrial processing. But the depletion of this vital resource has become a global concern due to uncontrolled anthropogenic influence. Poor environmental conditions arising from inadequate or non-existing wastewater management pose significant threats to human health, well-being and economic activity.

On average, high-income countries treat about 70% of generated wastewater, while low-income countries treat only 8% (United Nations 2017). Agricultural and industrial activities pose a major pollution threat to waters, and within industry textile manufacturing leads by being the largest polluter in the world (Babu et al. 2007). Major pollutants in textile wastewaters are high suspended solids (SS), chemical oxygen demand (COD), heat, colour, acidity, and other soluble substances

(Mondal et al. 2017).

In Ethiopia, the textile industry sector is undergoing a major development, growing on average by 51% in the last 5–6 years (Pols 2015), but this change has a serious negative impact in terms of pollution. Yirgalem Addis textile factory is one of the industries with complex composition of wastewater containing high values of 5-day biological oxygen demand (BOD 5), COD, total suspended solids (TSS), lead (Pb), and turbidity. As a solution, the industry implemented a treatment plant with conventional coagulation-flocculation, using synthetic coagulants and flocculants at a high cost.

In addition to its high cost and availability problems, conventional synthetic polyacrylamide is used as a flocculation agent, even though there are concerns around its toxicity because of un-polymerized carcinogenic monomer present in it (Xu et al. 2014).As a result, research has been conducted on the performance of natural plant extracts in water and wastewater clarification in order to substitute the synthetic flocculant. Plant-based coagulants such as mustard seed extract (Bodlund et al. 2014), rice starch (Teh et al. 2014), guar gum (Mukherjee et al. 2013), banana stem juice (Ku Hamid 2013), Moringa oleifera (Muthuraman & Sasikala 2014), Cassia obtusifolia seed gum (Subramonian et al. 2014) and others have been studied. But when it comes to applicability, one universal natural flocculant is not available because they are limited in certain areas and some are limited by seasons. Therefore, each country should evaluate the potential as well as to develop appropriate methods for natural polymer production. This research evaluates the efficiency of Aloe steudneri gel which is a succulent plant belonging to liliacea family as flocculant in treatment of textile wastewater.

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