Abstract
In many low-income countries, the poor conditions of sanitation systems have been a significant cause of mortality since they accelerate waterborne disease transmission. Developing sanitation systems in these countries is a pressing concern in both the public and private sectors.This research investigated a decentralized domestic wastewater treatment system using ultraviolet light-emitting diodes (UV-LEDs). Although UV-LED disinfection has become more widespread in recent years, it is a novel approach for domestic wastewater treatment. Domestic wastewater was pretreated by a low-cost pretreatment system with an inclined settler and a sand filter prior to feeding a novel flow-through UV LED reactor. At an inlet flow rate of 30 L/h, the COD, TSS, and turbidity of the effluent were 17.7 mg/L, 3.0 mg/L, and 3.9 NTU, respectively. UV transmittance at 285 nm was enhanced from 29.1% to 70.4%, improving the influent quality for UV LED disinfection.The flow-through UV LED reactor was operated at various flow rates from 10 to 50 mL/min, resulting in applied UV doses of 69.4 to 47.8 mJ/cm2 respectively. These doses are sufficient for inactivating total coliforms in the wastewater to meet the water reuse guidelines for agriculture for both processed food crops and non-food crops.Fouling, which was observed starting at 2 d of operation, decreased the disinfection efficacy to 27% after 25 days of continuous operation. Of the fouling layer, 67% was attributed to organic matter, in contrast to previous fouling studies with mercury UV lamps in which the fouling layer consisted primarily of inorganic compounds. The fouling was reversed by off-line citric acid cleaning for 4 h after every 400 h of continuous operation.
Highlights
In a recent study, more than 380 disease outbreaks related to waterborne parasitic protozoa were documented globally in a sixyear period between 2011 and 2016 (Efstratiou et al, 2017)
87% of total global mortality cases attributed to diarrhea came from South Asia and Sub-Saharan Africa (Troeger et al, 2017)
Domestic wastewater was collected from a manhole at the Asian Institute of Technology's (AIT) sewer system (Pathumthani Province, Thailand)
Summary
More than 380 disease outbreaks related to waterborne parasitic protozoa were documented globally in a sixyear period between 2011 and 2016 (Efstratiou et al, 2017). 87% of total global mortality cases attributed to diarrhea came from South Asia and Sub-Saharan Africa (Troeger et al, 2017). There is no doubt that poor water supply and sanitation systems are a root cause leading to these public health issues (Yang et al, 2012). Developing sanitation systems, especially disinfection processes, plays a critical role in addressing the issue. T.M.H. Nguyen et al / Water Research 153 (2019) 53e62
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