Investigating effectiveness of cactus mucilage on water bacteria aggregation.

Abstract

Flocculants are mostly used where solid-liquid separations are required in wastewater and potable water production facilities. Conventional flocculants include inorganic metal salts and synthetic organic polymers. The cost, availability, and effects of nonbiodegradable nature of these flocculants have led to the widespread study of natural flocculants. Current natural flocculants being studied are plant-based materials. In this study, the extract of Opuntia Ficus-indica cactus was evaluated as a natural flocculant for bacteria and floating sediment. The Opuntia. Ficus-indica cactus is also known as the nopal or prickly pear. Using simple extraction techniques non-gelling (NE) mucilage extracts were isolated from fresh cactus pads. Laboratory tests were used to determine the flocculation and removal of suspended sediment and bacteria caused by mucilage dosing. Throughout this study the mucilage’s potential as a flocculant was evaluated by varying its concentration on synthetic water prepared from kaolin and raw water The extracts consist primarily of polysaccharides and differences in physical structure between mucilage types were seen using atomic force microscopy and transition electron microscopy. Cactus extract is an effective natural coagulant which can be used in improving the physicochemical and bacteriological parameters of water in terms of pH, turbidity and conductivity. During coagulation process, cactus coagulant doesn’t much affect pH of water as it remains within recommended range. This is reducing the high cost of the current water treatment systems where there is a need of adjusting pH of water after each water treatment. Bacterial reduction was due to antimicrobial agent in cactus extract as well as settling time. Cactus extract protein produce a positive charge in water that acts attract dominant negatively charged particles like microbes to form flocs. Antimicrobial peptides extract act by disrupting bacterial cell membranes inhibiting essential enzymes of gram negative and gram positive. Also, bacterial removal was due to alkaline condition produced by cactus extract which inhibit the growth of acidophiles and extreme alkaliphiles Cactus cladodes can be qualified as natural flocculant in water treatment due to its effectiveness, moreover it minimizes the use of chemical flocculants. Therefore, its efficacy was further explored. Mucilage was most effective with dosages of Cactus mucilage extract concentration of 2.450g dissolved in 50ml of distilled water (0.049g/ml) for the parameters in raw water sample. Using the optimal concentration of 2ml of extract solution, 1 litter of raw of water could be treated with only 49 g of mucilage powder. Based on the extraction method used in this work, 1 g of mucilage powder can be obtained from a cactus pad weighing approximately 10 g (wet weight) of cactus cladodes. Mucilage remained an effective flocculant over a wide range of suspended contaminant concentrations showing that mucilage is a versatile flocculant that can be tailored for a variety of applications. Overall, this work shows that the O. Ficus Indica cactus is an effective flocculant for suspended sediments and bacteria where bacteria aggregation efficiency was 84.55%.