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

Abstract

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 This study aimed to sanitize compost withdrawn from the composting toilet for food production by setting post-treatment conditions.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.

Achilles heel of environmental risk from recycling of sludge to soil as amendment: A summary in recent ten years (2007–2016)

“…Pathogen microorganism in sludge and the change in vitality when sludge is harmless treated followed by being recycled to soil Sludge contains broad-spectrum profile of pathogenic microorganisms due to originating from domestic sewage, which is abundant in all kinds of bacteria (Arora et al, 2014;Li et al, 2015;Scheinemann et al, 2015), such as fecal coliform (Cabanas-Vargas et al, 2013;Ozdemir et al, 2013;Rhodes et al, 2015), Salmonella coli (Bonetta et al, 2014;Cabanas-Vargas et al, 2013;Levantesi et al, 2015), Escherichia coli (Levantesi et al, 2015;Verbyla et al, 2016;Pascual-Benito et al, 2015). In addition, there are a plenty of ascaris egg in sludge because most of its solid constitute is mainly from human faeces (Darimani et al, 2016;Verbyla et al, 2016;Fidjeland et al, 2015Fidjeland et al, , 2013. Main pretreatment measures are usually employed prior to recycling to soil, such as aerobic compost and anaerobic digestion, which are effective in inactivating or eliminating most of their vitalities (Cabanas-Vargas et al, 2013;Kjerstadius et al, 2013;Sreesai et al, 2013).…”

Post-Treatment and Microbial Risk Assessment of Compost for Food Production

“…For investigating the effect of temperature, 3 temperature levels, such as −5°C lower temperature as S2, −10°C lower temperature as S3 and −15°C lower temperature as S4 derived from the temperature measured in the steel box, were considered in this simulation, because the temperature varied by weather conditions. For the calculation of concentration in the compost, the inactivation rates coefficient from the previous measurement were used [6]. The details of the ingestion model are as follows: • To consider the worst case, 50,000 eggs/g in wet faeces is excreted from a heavily infested person [7].…”

Design of Post-Treatment Unit for Compost from a Composting Toilet with Microbial Risk Assessment

“…The estimated number of days was assumed to be 9 days, 6 days and 3 days for 40°C, 50°C and 60°C respectively. The estimated inactivation rate coefficient values for 40°C, 50°C and 60°C were 0.22 h -1 , 0.92 h -1 and 1.22 h -1 respectively, for Ascaris eggs and MS2 k values were 0.25 h -1 , 0.45 h -1 and 0.80 h -1 [4,5].…”

“…We set 6 scenarios, the compost at constant temperatures (40°C, 50°C and 60°C, S-1 to S-3) and actual temperature at 3 positions (1 cm, 5 cm and 10 cm from the surface) in the steel box (S-4 to S-6) as a post-treatment for the assessment. For the calculation of concentration in the compost, the inactivation rate coefficient from our previous measurement was used [4,5]. The details of the ingestion model are as follows:…”

“…The steel box is painted black in colour to aid in the absorption of heat. The steel box does not have a solar concentrator [3,4,5]. The temperature distribution of the compost in the box was measured at 3 positions which were 1 cm, 5 cm, and 10 cm from the surface.…”