Eau et développement

In many low-income countries, the poor conditions of sanitation systems have been a significant cause ofmortality since they accelerate waterborne disease transmission. Developing sanitation systems in thesecountries is a pressing concern in both the public and private sectors.
This research investigated a decentralized domestic wastewater treatment system using ultravioletlight-emitting diodes (UV-LEDs). Although UV-LED disinfection has become more widespread in recentyears, it is a novel approach for domestic wastewater treatment. Domestic wastewater was pretreated bya low-cost pretreatment system with an inclined settler and a sand filter prior to feeding a novel flowthroughUV LED reactor. At an inlet flow rate of 30 L/h, the COD, TSS, and turbidity of the effluent were17.7 mg/L, 3.0 mg/L, and 3.9 NTU, respectively. UV transmittance at 285 nm was enhanced from 29.1% to70.4%, 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 inapplied UV doses of 69.4 to 47.8 mJ/cm² respectively. These doses are sufficient for inactivating totalcoliforms in the wastewater to meet the water reuse guidelines for agriculture for both processed foodcrops 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, incontrast to previous fouling studies with mercury UV lamps in which the fouling layer consisted primarilyof inorganic compounds. The fouling was reversed by off-line citric acid cleaning for 4 h afterevery 400 h of continuous operation.

Sustainable Development Goal (SDG) Indicator6.2.1 requires household handwashing facilities to havesoap and water, but there are no guidelines for handwashingwater quality. In contrast, drinking water quality guidelines aredefined: water must be “free from contamination” to bedefined as “safely managed” (SDG Indicator 6.1.1). Wemodeled the hypothesized mechanism of infection due tocontaminated handwashing water to inform risk-based guidelinesfor microbial quality of handwashing water. We definedtwo scenarios that should not occur: (1) if handwashingcaused fecal contamination, indicated using Escherichia coli, ona person’s hands to increase rather than decrease and (2) ifhand-to-mouth contacts following handwashing caused aninfection risk greater than an acceptable threshold. We found water containing <1000 E. coli colony-forming units (CFU) per100 mL removes E. coli from hands with>99.9% probability. However, for the annual probability of infection to be <1:1000,handwashing water must contain <2 × 10⁻⁶ focus-forming units of rotavirus, <1 × 10⁻⁴ CFU of Vibrio cholerae, and <9 × 10⁻⁶Cryptosporidium oocysts per 100 mL. Our model suggests that handwashing with nonpotable water will generally reduce fecalcontamination on hands but may be unable to lower the annual probability of infection risks from hand-to-mouth contactsbelow 1:1000.

Processing of biowaste with larvae of the black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae), is an emerging waste treatment technology. Larvae grown on biowaste can be a relevant raw material for animal feed production and can therefore provide revenues for financially viable waste management systems. In addition, when produced on biowaste, insect-based feeds can be more sustainable than conventional feeds. Among others, the scalability of the technology will depend on the availability of large amounts of biowaste with a high process performance (e.g. bioconversion of organic matter to proteins and lipids) and microbial and chemical product safety. Currently, in contrast to other waste treatment technologies, such as composting or anaerobic digestion, the process performance is variable and the processes driving the decomposition of biowaste macronutrients, inactivation of microbes and fate of chemicals is poorly understood. This review presents the first summary of the most important processes involved in black soldier fly larvae (BSFL) treatment, based on the available knowledge concerning five well-studied fly species. This is a starting point to increase understanding regarding the processes of this technology, with the potential to increase its efficiency and uptake, and support the development of appropriate regulations. Based on this review, formulating different types of biowaste, e.g. to produce a diet with a similar protein content, a balanced amino acid profile and/or pre- and co-treatment of biowaste with beneficial microbes, has the potential to increase process performance. Following harvest, larvae require heat or other treatments for microbial inactivation and safety.

The study assessed changes in water quality between the water source and the tap of locally produced low cost ceramic water filters used by a community living in hygienically critical conditions in a remote mountainous area in Western Nepal. Data was collected from 42 rural households during two visits. The effectiveness of filter handling on its performance was assessed through microbiological analysis, structured household interviews and structured observations. Water quality decreased significantly when source water was filled into transport containers, while the use of the filters improved drinking water quality for about 40% of the households. Highly inadequate filter cleaning practices involving the use of contaminated raw water, hands (geo mean = 110 E. coli CFU/100 mL) and cleaning tools (geo mean = 80 E. coli CFU/100 mL) stained hygienic parts of the filter. The use of boiling water to disinfect the filters was significantly correlated with improved filter performance and should be further promoted. However, even disinfected filters achieved a very low average LRV for E. coli of 0.4 in the field and performed worse than during laboratory tests (LRV for E. coli of 1.5-2). Comprehensive training on adequate filter handling, as well as better filter products, are required to improve the impact of filter use.