Wastewater treatment with Moringa oleifera seed extract: Impact on turbidity and sedimentation of Cryptosporidium parvum oocysts

Abstract

The use of low quality water for irrigation in agriculture is common practise in many countries due to limited freshwater resources. Pathogens may contaminate vegetables when faeces polluted water is used for irrigation. A laboratory study was carried out to investigate the effect of a coagulant produced from seeds of the Moringa oleifera tree (MO) in reducing Cryptosporidium parvum oocysts and turbidity in wastewater. To a total of 5 x 12 glass jars containing 500 ml wastewater samples from a Danish treatment plant, 1.2 x 106 ± 1.2 x 105 oocysts L-1 were added. To half of the wastewater samples 8 ml L-1 of a 5% w/v MO seed extract was added, while the remaining wastewater samples were left untreated. The samples were stirred slowly for 20 min and subsequently left to settle for 15, 30, 45, 60 or 90 min, with six replicate glass jars representing each time point. In both treated and untreated wastewater, most oocysts settled within the first 15 min, while the sedimentation was negligible between 15 and 90 min. Nevertheless, MO seed extracts were effective in reducing the number of C. parvum oocysts significantly (p=0.026) by 38% in the interval 15 to 90 min as compared to a 0.02% reduction in the untreated wastewater. Furthermore, the number of oocysts L-1 was significantly (p<0.005) lower in the treated wastewater at all 5 sampling times compared to untreated wastewater. The turbidity was reduced to 9.8 ± 1.8 NTU (i.e. 95% reduction) in the treated water, which was significantly (p<0.0001) lower than the lowest turbidity values of 57.7 ± 4.2 (i.e. 72% reduction) seen in the untreated water. MO seeds are readily available in many tropical countries where the tree is common, and our results document that the seed extract may be used by farmers for treatment of different types of surface water. Yet, the study did not succeed in removing all oocysts from the wastewater after treatment, which was probably caused by an imbalance between the relative concentration of oocysts and MO seed extract with more oocysts present than the seed extract could adhere to. However, treatment of wastewater with MO seed extract significantly improved the water quality with regard to number of oocysts present and turbidity of the water. Further experiments with water samples containing fewer C. parvum oocysts are needed to establish whether MO seed extract can be used to effectively treat and obtain safe water free of C. parvum oocysts as well as other protozoan parasites.