S. Katayon

Preservation of coagulation efficiency ofMoringa oleifera, a natural coagulant

In recent years, there has been an interest to useMoringa oleifera as the natural coagulant due to cost, associated health and environmental concerns of synthetic organic polymers and inorganic chemicals. However, it is known thatM. oleifera as the natural coagulant is highly biodegradable and has a very short shelf life. This research was carried out to investigate the effects of storage temperature, packaging methods, and freeze-drying on the preservation ofM. oleifera seeds powders. Non freeze-driedM. oleifera was prepared into different packaging namely open container, closed container and vacuum packing, whilst, freeze-driedM. oleifera was stored in closed container and vacuum packing. Each of the packaging was stored at room temperature (30 to 32°C) and refrigerator (4°C). The turbidity removal efficiencies of storedM. oleifera were examined using jar test at monthly interval for 12 months. The results indicated that non freeze-driedM. oleifera kept in the refrigerator (4°C) would preserve its coagulation efficiency. In addition, closed container and vacuum packing were found to be more appropriate for the preservation of non freeze-driedM. oleifera, compared to open container. Freeze-driedM. oleifera retained its high coagulation efficiency regardless the storage temperature and packaging method for up to 11 months. Besides, higher increment in zeta potential values for water coagulated with freeze-driedM. oleifera indicated the higher frequency of charge neutralization and better coagulation efficiency of freeze-driedM. oleifera, compared to non freeze-dried seeds. As a coagulant,M. oleifera did not affect the pH of the water after treatment.

Treatment of mild domestic wastewater using subsurface constructed wetlands in Malaysia

This study presents the design and performance of pilot scale constructed wetlands in treating a mild domestic wastewater generated from the Faculty of Engineering, Universiti Putra Malaysia. Three cells of subsurface constructed wetlands were built in equal dimensions, two cells were planted with Lepironia articulata, an indigenous Malaysian aquatic plant, while one cell was left unplanted to investigate the role of the plant in treatment process. Those cells were operated at four different hydraulic retention times in two phases ranged from 0.5 to 7 days. The results showed that the constructed wetlands were capable of removing about 56–77% of COD, 50–88% of TSS, 20–88% of TP, 27–96% of NH4 + and 99% of total coliforms numbers. Different hydraulic retention times caused significant effect on removal rate of COD, TP and NH4 +, but not to TSS and total coliforms removal. The total number of coliforms was positively correlated with concentration of COD, TP and NH4 + in effluents. Planted wetland cells were superior in both NH4 + and TP removal to unplanted wetland cells.