Greywater Treatment by High Rate Algal Pond under Sahelian Conditions for Reuse in Irrigation

Abstract

High Rate Algal Pond (HRAP) was constructed and operated using a mixer device to investigate its capability in treating greywater for reuse in gardening. Physico-chemical and microbiological parameters were monitored. With a hydraulic retention time of 7.5 days and a solid retention time of 20 days, the average removal efficiencies (ARE) were 69% and 62% for BOD5 and COD respectively. The ARE for 3 NO − , 4 NH + and 4 PO 3− were 23%, 52% and 43% respectively. The removal of suspended solids (SS) was unsatisfactory, which could be attributed to the low average algal settling efficiencies of 9.3% and 16.0% achieved after 30 and 60 minutes respectively. The ARE of fecal coliforms, Escherichia coli and enterococci were 2.65, 3.14 and 3.17 log units respectively. In view of the results, the HRAP technology could be adapted for greywater treatment in sahelian regions. However, further studies on the diversity of the algal species growing in the HRAP unit are necessary in order to increase the removal of SS. Hazards of a reuse of the effluents are discussed on the basis of the various qualitative parameters. The residual content of E. coli was varying from <1 to 1.77 × 10 4 CFU per 100 mL. Based on WHO guidelines for greywater reuse in irrigation, the effluents could be used for restricted irrigation (E. coli < 10 5 CFU per 100 mL). Furthermore, the reuse potential is discussed on the basis of FAO guidelines using SAR (3.03 to 4.11), electrical conductivity (482 to 4500 µS/cm) and pH values (6.45 to 8.6).

Elevated levels of anthropogenic antibiotic resistance gene marker, sul1, linked with extreme fecal contamination and poor water quality in wastewater‐receiving ponds

“…was typically not used for drinking or fishing and was only occasionally used for irrigation (Datta et al, 2021;Maiga et al, 2015). In the water, sediment, and adjoining soil samples, we quantified the DNA markers of the fecal indicator (Escherichia coli) to investigate the persistence of fecal bacteria; 16S rRNA gene copies to track the trends in the total bacterial count; and the anthropogenic antibiotic resistance gene markers-intI1, sul1, to investigate the overall trends in antibiotic resistance potential in WRPs.…”

“…We sampled seven WRPs and contrasted them with two ponds (sites H and I) that did not directly receive domestic wastewater and were used for irrigation (P–I) and pisciculture (P–P), respectively. We observed that the water from the targeted WRPs was typically not used for drinking or fishing and was only occasionally used for irrigation (Datta et al., 2021; Maiga et al., 2015). In the water, sediment, and adjoining soil samples, we quantified the DNA markers of the fecal indicator ( Escherichia coli ) to investigate the persistence of fecal bacteria; 16S rRNA gene copies to track the trends in the total bacterial count; and the anthropogenic antibiotic resistance gene markers— int I1, sul 1, to investigate the overall trends in antibiotic resistance potential in WRPs.…”

Effects of potassium and carbon addition on bacterial algae bioremediation of boezem water

“…Nutrients and carbondioxide (CO 2 ) from oxidation will be used by algae. HRAP waste treatment has some benefits that it is cost-effective and algae energy is converted to biofuel, biogas, and bio-ethane as biofuels [7], its reproduction is fast, non-pathogenic, the range of toxicity is extensive [8], useful for environmental sustainability [5], and environmentally friendly [9].…”

“…Several studies that have been conducted to examine the ability of microalgae in remediating polluted environments among others are HRAP in managing greywater on average can reduce biological oxygen demand (BOD 5 ) to 69%, chemical oxygen demand (COD) to 62%, NO 3 to 23%, NH 4 to 52%, PO 4 to 43% [7]. Bioremediation of Porphyra leucosticta red algae can reduce metals Cd(II) and Pb(I) with maximum capacities of 31.45 mg/g and 36.63 mg/g, respectively [10], Scenedesmus sp.…”