Fecal sludge treatment in a pilot-scale vertical-flow constructed wetland for the removal of helminth eggs

Abstract

Eliminating parasites in fecal sludge (FS) remains one of the major concerns in developing countries. To address this issue, experiments were conducted in triplicate vertical-flow constructed wetland (VFCW) units corresponding to free flow, 7 days and 14 days of retention time (RT). The effect of plant density on the system's performance was monitored in each planted bed unit and compared to the non-planted unit (standard). Following a bi-monthly application rate of FS at a nominal load of 200 kg TS m−2 year−1, the performance of the system in terms of helminth egg removal was calculated for each hydraulic RT tested. Untreated FS applied on the bed units contained high parasitic egg loads with a median number of 62.51 helminth eggs/g. The removal efficiencies of helminth eggs ranged from 82 to 100% in the leachates and were affected by the hydraulic RTs and the presence of plants (p < 0.05). On the other hand, accumulated biosolids on the bed units still contained high concentrations of pathogens exceeding the WHO standards and should not be applied directly in agriculture.

Assessment of pathogen removal efficiency of vertical flow constructed wetland treating Septage

“…Vertical subsurface ow CWs offer favourable oxygen transfer conditions and encourage nitri cation 15 . Previous studies support the results by showing effective removal e ciency of CW systems in case of pathogens like coliform 13,16,17 and helminths eggs 4,18,19 along with reduction in BOD 13 , COD 8 , TDS 20 and TS 8 . Hybrid Imhoff tank and CW systems effectively removed total coliform and parasitic eggs by 99% from the wastewater, making the treated e uent t for irrigation purpose 5 .…”

“…Parallel wetland cells with several plant species, including Phragmites ,Typha and Cyperus removed 100% of the helminths eggs and 99.8% of protozoa 18 . Plantation and hydraulic retention time (HRT) are directly related to removal e ciency of constructed wetlands 4 . silex, granite and river gravel were used as ltration bed media with plant species Phragmites and Typha in CW system to treat municipal raw wastewater and the results showed signi cant decrease in organic and microbial pollutants.…”

“…Untreated septage is released into rivers and streams in India, causing them to deteriorate and become un t for use. Septage contains numerous pathogens such as various coliforms 1,2 and helminths eggs 3,4 which have detrimental effects on human health once they reach into the body. Rise in temperature and run-off after precipitation increase the quantity of pathogens in the water body where septage is discharged.…”

Assessment of pathogen removal efficiency of vertical flow constructed wetland treating septage

“…Untreated septage is released into rivers and streams in India, causing them to deteriorate and become unfit for use. Septage contains numerous pathogens such as various coliforms 1 , 2 and helminthes eggs 3 , 4 which have detrimental effects on human health once they reach into the body. These pathogens are difficult to remove by conventional wastewater treatment methods 5 .…”

“…Among the sub-surface flow CW designs, most popular designs are vertical flow 8 – 10 , horizontal flow 11 , 12 , tidal flow and hybrid designs of CWs. Constructed wetlands have established their effectiveness in the removal of pathogens and various pollutants 4 , 5 . In the recent past, vertical flow CW systems have gained more attention for their effectiveness in septage treatment.…”