Effectiveness of crude extract and purified protein from Vigna unguiculata seed in purification of charco dam water for drinking in Tanzania
2013
Marobhe, Nancy Jotham
Due to chronic water supply problems prevailing in most rural areas of Tanzania, households are obliged to use man made water reservoirs (charco dams) for drinking after receiving inadequate treatment using powdered seeds from different plant species. This study is aimed at investigating the capacity of crude extract and purified proteins (coagulant proteins) from Vigna unguiculata (VUP) seed to purify drinking water from Nunguru charco dam. Coagulant proteins were purified from V. unguiculata crude seed extract (VUCE) by modified ion exchange chromatography technique. The VUP were found to be cationic in nature and have the molecular mass of about 6 kDa, which is very similar to the coagulant proteins purified from Moringa oleifera and Parkinsonia aculeata seeds. The coagulation potentials of VUP and VUCE were verified by jar experiments and the performances were compared to those of aluminium sulphate (alum) using water samples with initial turbidity of 880 NTU. The coagulant proteins reduced most pollutants to the levels that complied with the Tanzania Drinking Water Standards and WHO standards. Minimum residual turbidity achieved by both VUCE and VUP was 3 NTU and 12 NTU for alum. The VUP performed best at the dosage of 8 mg/L which was almost ten times lower than that observed for VUCE (76 mg/L). The VUP reduced organic load in treated water by 80% while VUCE increased it by almost 100%. Although the VUP and VUCE did not alter the pH and alkalinity of the treated water, the VUP increased the conductivity of water substantially without affecting the water palatability. The VUP and VUCE reduced Fe²⁺ in coagulated by 93 - 98% while NO₃⁻ and PO₄³⁻ were reduced by 91 – 99% and 94 - 99.6%, respectively. The VUP and alum reduced fecal indicators by 94 and 98.6% respectively. The purification procedure of coagulant proteins is simple and user friendly and hence it could be scaled up for large scale production of coagulant proteins for use in water treatment processes in Tanzania. The VUCE and VUP are recommended for production of drinking water and other domestic uses so as to reduce the incidences of cholera and improve people's health and hygiene.
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