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On-Site Fecal Sludge Treatment with the Anaerobic Digestion Pasteurization Latrine

View Article: PubMed Central - PubMed

ABSTRACT

The Anaerobic Digestion Pasteurization Latrine (ADPL) is a self-contained and energy neutral on-site sanitation system using anaerobic digestion of fecal sludge to generate biogas and then uses the biogas to pasteurize the digester effluent at 65–75°C to produce a safe effluent that can be reused locally as a fertilizer. Two ADPL systems were installed on residential plots with 17 and 35 residents in a peri-urban area outside of Eldoret, Kenya. Each system comprised three toilets built above a floating dome digester and one heat pasteurization system to sanitize the digested effluent. ADPLs are simple systems, with no moving parts and relying on gravity-induced flows. Adoption at the two sites was successful, and residents reported that the systems had little to no odor or flies. ADPLs were monitored for biogas production and temperatures in the pasteurization system. ADPLs serving 17 and 35 residents produced on average 16 and 11 Lbiogas/person/day (maximum of 20 and 15 Lbiogas/p/d), respectively. The temperature in the sterilization system was greater than 65°C on 58% and 87% of sampling days during the most stable period of operation. Treated effluent was analyzed periodically for chemical oxygen demand (COD), biochemical oxygen demand (BOD), total ammonia nitrogen (TAN), pH, and fecal coliform (FC). On average, the effluent at the two locations contained 4,540 and 6,450 mg COD/L (an 85% or 89% reduction of the estimated input), 2,050 and 3,970 mg BOD/L, and 2,420 and 4,760 mg NH3-N, respectively, and greater than 5 log reductions of FC (nondetectable) in the sterilization tank. Results from this field study show that anaerobic digestion of minimally diluted fecal sludge can provide enough energy to pasteurize digester effluent and that the ADPL may be a suitable option for on-site fecal sludge treatment.

No MeSH data available.


Related in: MedlinePlus

Daily temperature measurements from outlet of cold chamber of heat exchanger (point No. 2). This point is also the inlet of the heater.
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f4: Daily temperature measurements from outlet of cold chamber of heat exchanger (point No. 2). This point is also the inlet of the heater.

Mentions: During the June 2015 to March 2016 period, a greater number of blockages in the digester outlet and heating system were observed together with an accumulation of solids in the heating system. These issues are all believed to be due to an increased amount of solids leaving the digester after 2.5 years of operation without desludging. Accumulated solids settling in the heater and in the heat exchanger were most probably reducing heat transfer due to lower liquid residence times and fouling of surfaces. These effects were not quantified, but their occurrence correlates with the inconsistent temperature measurements seen in Fig. 3, as well as decreasing trend of temperatures at the cold effluent port (point T2) shown in Fig. 4.


On-Site Fecal Sludge Treatment with the Anaerobic Digestion Pasteurization Latrine
Daily temperature measurements from outlet of cold chamber of heat exchanger (point No. 2). This point is also the inlet of the heater.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5134843&req=5

f4: Daily temperature measurements from outlet of cold chamber of heat exchanger (point No. 2). This point is also the inlet of the heater.
Mentions: During the June 2015 to March 2016 period, a greater number of blockages in the digester outlet and heating system were observed together with an accumulation of solids in the heating system. These issues are all believed to be due to an increased amount of solids leaving the digester after 2.5 years of operation without desludging. Accumulated solids settling in the heater and in the heat exchanger were most probably reducing heat transfer due to lower liquid residence times and fouling of surfaces. These effects were not quantified, but their occurrence correlates with the inconsistent temperature measurements seen in Fig. 3, as well as decreasing trend of temperatures at the cold effluent port (point T2) shown in Fig. 4.

View Article: PubMed Central - PubMed

ABSTRACT

The Anaerobic Digestion Pasteurization Latrine (ADPL) is a self-contained and energy neutral on-site sanitation system using anaerobic digestion of fecal sludge to generate biogas and then uses the biogas to pasteurize the digester effluent at 65–75°C to produce a safe effluent that can be reused locally as a fertilizer. Two ADPL systems were installed on residential plots with 17 and 35 residents in a peri-urban area outside of Eldoret, Kenya. Each system comprised three toilets built above a floating dome digester and one heat pasteurization system to sanitize the digested effluent. ADPLs are simple systems, with no moving parts and relying on gravity-induced flows. Adoption at the two sites was successful, and residents reported that the systems had little to no odor or flies. ADPLs were monitored for biogas production and temperatures in the pasteurization system. ADPLs serving 17 and 35 residents produced on average 16 and 11 Lbiogas/person/day (maximum of 20 and 15 Lbiogas/p/d), respectively. The temperature in the sterilization system was greater than 65°C on 58% and 87% of sampling days during the most stable period of operation. Treated effluent was analyzed periodically for chemical oxygen demand (COD), biochemical oxygen demand (BOD), total ammonia nitrogen (TAN), pH, and fecal coliform (FC). On average, the effluent at the two locations contained 4,540 and 6,450 mg COD/L (an 85% or 89% reduction of the estimated input), 2,050 and 3,970 mg BOD/L, and 2,420 and 4,760 mg NH3-N, respectively, and greater than 5 log reductions of FC (nondetectable) in the sterilization tank. Results from this field study show that anaerobic digestion of minimally diluted fecal sludge can provide enough energy to pasteurize digester effluent and that the ADPL may be a suitable option for on-site fecal sludge treatment.

No MeSH data available.


Related in: MedlinePlus