Vol.:(0123456789) 1 3 International Journal of Environmental Science and Technology https://doi.org/10.1007/s13762-018-1844-2 ORIGINAL PAPER Comparison of purifed and crude extracted coagulants from plant species for turbidity removal M. Megersa 1,2  · A. Beyene 1  · A. Ambelu 1  · L. Triest 2 Received: 25 July 2017 / Revised: 3 November 2017 / Accepted: 12 June 2018 © Islamic Azad University (IAU) 2018 Abstract The coagulation properties of crude extracts and purifed proteins of seeds of Moringa stenopetala and tubers of Maerua sub- cordata, which are locally used for purifcation of turbid water in Ethiopia, were studied. The turbidity removal efectiveness was compared using synthetic turbid and natural river water where the initial turbidity of synthetic water was approximately 260 NTU, whereas, for river water, the initial turbidity was 30 NTU. The active coagulants from the extracts were purifed by the single-step and the two-step ion exchange (IEX) chromatography technique using 0.1, 0.3 and 0.6 M concentrations of NaCl solutions. The protein quantifcation of a single-step purifed active coagulant eluted using 0.6 M showed that the protein content of the M. stenopetala extract was 1016 µg/mL, whereas the concentration of the M. subcordata extract was 700 µg/mL. The dose for coagulation using crude extracts and purifed proteins of M. subcordata on surface water was 4 and 2 mg/L, respectively, with 85% of coagulation activity. In the case of M. stenopetala, 14 mg/L dose of crude extracts, which was seven times higher than that of the purifed protein, was needed to obtain the desired residual turbidity (5 NTU). The results also indicated that in the two-step purifed coagulants, the sludge volume was reduced compared to crude extracts and alum. In conclusion, active coagulants from seeds of M. stenopetala could be scaled up and used in water treatment technology, whereas purifying the extracts from M. subcordata is not required as the crude extracts performed equally well. Keywords Coagulation · Extraction · Maerua subcordata · Moringa stenopetala · Natural coagulants · Water treatment Introduction The impurities present within the source water may take the form of dissolved and colloidal natural organic matter, dis- solved salts or suspended material, along with clays, silica, microbial cells or algae (Bolto and Gregory 2007). These dissolved and suspended particles present in most natural waters usually have a net negative surface charge (Edzwald and Tobiason 1999). Such materials must be removed from potable supplies, as they cause deterioration of water quality by reducing the clarity (i.e., causing turbidity). Moreover, they should be removed from water as the surface could pro- tect microorganisms from the action of disinfection agents (Saranya et al. 2013). Treatment of water to remove turbidity is essential for large- and small-scale production of drink- ing water. One of the frst processes in water treatment is coagulation (Renault et al. 2009). One of the widely used chemical coagulants in water treatment industry is aluminum sulfate (alum). However, alum has been reported to have negative impacts on envi- ronment and human such as production of large sludge volumes (Vijayaraghavan et al. 2011), reduction in pH (Oladoja 2015), and correlated with Alzheimer’s dis- ease in experiments involving mice and humans (Ribes et al. 2008; Rondeau et al. 2009; Bondy 2014; Wang et al. 2016). Furthermore, intensive chemical treatments and residuals resulting from these treatments can add to the problems of contamination and salinization of fresh-water sources (Shannon et al. 2008). At present, there remain signifcant challenges to the water utilities in the develop- ing and developed world in terms of fully complying with existing water quality regulations (Ghernaout et al. 2011). Editorial responsibility: M. Abbaspour. * M. Megersa moamegersa78@gmail.com 1 Department of Environmental Health Science and Technology, Jimma University, P.O.Box: 378, Jimma, Ethiopia 2 Plant Biology and Nature Management (APNA), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium