Assessment on overall efficiency of urban greywater treatment by vermifiltration in hot climate: enhanced pollutants removal.

Vermifiltration technology using Eudrilus Eugeniae could be an alternative low-cost option for the treatment of urban greywater, which is highly polluted with high concentrations of surfactants, sodium and cooking oil. In this study, the effects of these pollutants on performance of a vermifiltration system was tested over a period of 6 to 8 weeks by enriching raw greywater with various concentrations of anionic surfactants (0, 15, 45 and 135 mg/L), sodium (0, 1, 2 and 4 g/L) and refined palm cooking oil (0, 250 and 500 mg/L). The vermifilter system was made of gravel, sand and sawdust layers from the bottom to the top, on which 200 earthworms were added. The greywater used in this study was previously used for dishwashing and laundry by an urban poor household. The greywater quality was compared with the effluent to evaluate the system performance. BOD5, COD, TSS and E. coli removal efficiencies ranged from 93% to 98%, 68% to 93%, 88% to 96% and 1.4-3 ULog, respectively, which are within the range of efficiencies reported in the literature. High proportion of surfactants (95-99%) and oil (84-89%) were removed but sodium was not removed. Instead, an increase in sodium concentrations was observed in the filter over the experimental period. Statistical analysis shows that BOD5, COD, TSS and E. coli removal efficiencies were independent of surfactants, cooking oil and sodium concentrations (p < .05). Thus, short term or accidental exposure of the vermifilter to high concentrations of these three pollutants did not have significant effect on the system performance.

Fate of filter materials and microbial communities during vermifiltration process.

The fate of filter materials and microbial communities during the vermifiltration process were studied for 5 months while treating the concentrated greywater. Four filters were filled with 10 cm gravel of which a layer of medium size gravel (5 cm thickness, aggregate size 20-40 mm) at the bottom and a layer of coarse gravel (5 cm thickness, aggregate size 10-20 mm) at the top, then filled with 20 cm sand (d60 = 0.2 mm, d10 = 0.118 mm). Finally, Vermifilter 1 (VF1), control unit and Vermifilter 2 (VF2), were filled with 40 cm fine sawdust (0.05-5 mm) but Vermifilter 3 (VF3), was filled with 40 cm cow dung (0.05-5 mm). Three filters were inoculated with 200 individuals of Eudrilus eugeniae except for the control unit which was filled with sawdust. Five sampling ports were installed on the wall of the filters at 10 cm intervals with reference to the surface of the top layer. Three of the filters were supplied with concentrated greywater and VF1 was supplied with drinking water at the hydraulic loading rate of 16 L m-2.d-1 on batch basis, i.e., four times a day at 8:00 a.m., 11:00 a.m., 2:00 p.m. and 5:00 p.m. Weekly, samples from influent and effluent, and monthly, samples of filter materials collected via sampling ports, were collected and analyzed.The removal efficiencies of biological oxygen demand (BOD5), total chemical oxygen demand (tCOD), and dissolved chemical oxygen demand (dCOD) of VF2 and VF3 were 5-7% higher than the control unit, but little differences were observed in terms of total suspended solids (TSS). However, the removal efficiencies of nutrients for the control unit was slightly better than VF2 and VF3. The pH and Moisture content (MC) of filter materials increased along the depth, but percentage of volatile solids to total solids (VS/TS) decreased through time due to the high number of microbial communities and earthworms dominating the top layer compared to the bottom. The performance of VF2-sawdust was slightly better than VF3-cow dung to treat concentrated greywater.

Effect of post-treatment conditions on the inactivation of helminth eggs (Ascaris suum) after the composting process.

Safe and appropriate disposal of human waste is a basic requirement for sanitation and protection of public health. For proper sanitation and nutrient recovery, it is necessary to ensure effective treatment methods to complete pathogen destruction in excreta prior to reuse. Composting toilets convert faeces to a reusable resource such as fertilizer or humus for organic agriculture. A composting toilet for rural Burkina Faso was created by modifying a commercial model available in Japan to improve hygiene and increase food production. The toilet has shown to result in a degraded final product, but its effectiveness for pathogen destruction was unclear due to low temperatures generated from the toilet. This study aimed to sanitize compost withdrawn from the composting toilet for food production by setting post-treatment conditions. The inactivation kinetics of Ascaris suum eggs, selected as an indicator for helminth eggs, was determined during post-treatment at different temperatures (30°C, 40°C, 50°C and 60°C) with varying moisture contents (MC) (50%, 60% and 70%). The treatment of compost in a possible additional post-treatment after the composting process was tried in the laboratory test. Inactivation of A. suum eggs was fast with greater than two log reductions achieved within 2 h for temperature 50°C and 50% MC and greater than three log reductions for temperature 60°C and 50% MC within 3 h. Statistical analysis showed the significant impact of temperature and moisture on the inactivation rates of A. suum eggs. The post-treatment can efficiently increase helminth eggs destruction prior to reuse.

Performance comparison of sand and fine sawdust vermifilters in treating concentrated grey water for urban poor.

A comparative investigation was conducted for 10 months with sand and fine sawdust vermifilters and a control unit to treat concentrated grey water generated from a poor urban household in Ouagadougou, Burkina Faso. Each of the filters was made up of cylindrical DN200-PVC pipes and filled with 10 cm of gravel at the bottom. On top of the gravel layer, filter 1 (fully sand, F1) was completed with 40 cm of sand and 10 cm of fine sawdust, filter 2 (partially sand, F2) with 20 cm of sand and 30 cm of fine sawdust, respectively, and filter 3 (fully sawdust, F3) and 4 (control, F4) with 50 cm of fine sawdust only. Two hundred Eudrilus eugeniae earthworms were inoculated in each of the vermifilters. The vermifiltration system was supplied with grey water four times per day at a hydraulic loading rate of 64 L/m(2)/day on a batch basis. The removal efficiencies of biological oxygen demand, total chemical oxygen demand, and dissolved chemical oxygen demand (dCOD) by the vermifilters were 25-30% higher than the control, but little differences were observed in terms of total suspended solids and coliform removal efficiencies. Though there was no significant difference in the performance of the three vermifilters (p > 0.05), except for dCOD removal efficiency, the lifespan of F2 and F3 was longer than that of F1. Therefore, fine sawdust can substitute sand as a filter medium in vermifilters.