Managing water in the home: accelerated health gains from improved water supply
Summary tables
Table 20. Comparison of Recommended Technologies for Household Water Treatment
| Criterion | Boiling with Fuel | Solar Disinfection with UV + Heat (SODIS or SOLAIR) | Solar Disinfection with Heat Only (Opaque Vessels and Solar Panels) | UV Disinfection with Lamps | Free Chlorine and Storage in an Improved Vessel ("CDC Safewater") | Chemical Coagulation-Filtration + Chlorine Disinfection |
| Microbial Reductions | Yes, extensive | Yes, extensive for most pathogens | Yes, extensive for most pathogens | Yes, extensive for most pathogens | Yes, extensive* for most pathogens | Yes, extensive |
| Diarrheal Disease Reductions | Yes | Yes, 9-26%; two studies | None reported from epid. studies, but expected due to high temperature (55+oC) | None reported from epid. Studies, but expected due to germicidal effects | Yes, 15-48%; many studies | None reported from epid. Studies yet, but expected due to multiple treatments |
| Disinfectant Residual | No | No | No | No | Yes | Yes |
| Quality Requirements of Water to be Treated | No | Low turbidity (<30 NTU) for effective use; pre-treat turbid water | None | Low turbidity (<30 NTU) and low in UV-absorbing solutes, such as NOM, iron and sulfites | Low turbidity (<30 NTU) and low chlorine demand for effective use; pre-treat turbid water | None; applicable to poor quality source water |
| Chemical changes in water | No, usually except deoxygenating and chemical precipitation | None or not significant | None or not significant | None or very little | Yes; may cause taste and odor and disinfection by-products | Yes, may cause taste and odor and disinfection by-products |
| Microbial regrowth potential in treated water | Yes, with storage beyond 1-2 days | Yes, with storage beyond 1-2 days | Yes, with storage beyond 1-2 days | Yes, with storage beyond 1-2 days | None to low if chlorine residual maintained | None to low if chlorine residual maintained |
| Skill level and ease of Use | Low skill, easy use | Low skill; very easy use | Low skill; easy use with training | Moderate skill, training needed for maintenance cleaning and lamp replacement | Low skill; easy use with training | Moderate, training needed in adding chemicals, mixing, decanting and filtering |
| Availability of Needed Materials | Requires a source of fuel | Requires plastic (PET) bottles and dark surface (on one side of vessel or on surface where vessel is placed | Requires black bottles of cook vessels and a solar reflector or solar cooker | Requires UV units and replacement lamps and a reliable source of electricity (power) | Requires source of free chlorine or chlorine generator and source of safe storage vessels | Requires a source of the chemical mixture (coagulants and chlorine disinfectant); may limit availability |
| Limits to Water Volume Treated | Yes, difficult to scale up above usual cooking volumes | Yes, treats 1-1.5 liters per bottle; can simultaneously treat multiple bottles | Yes, treats 1-4 liters per container; can simultaneously treat multiple vessels with multiple solar panels or solar cookers | No, units can treat several liters per minute and much, depending on lamp size and number and reactor volume | No, easily scaled up | Yes, chemical mixture treats fixed volumes of 10-20 liters; repeated treatment of additional volumes |
| Performance verification requirements | Observe water for a rolling boil | Measure that target temperature is reached (thermometer or wax indicator | Measure that target temperature is reached (thermometer or wax indicator) | Must verify lamp output; may be a limitation if unit lacks a UV sensor | Measure chlorine residual or microbial quality (indicators) or both | Observe (measure) turbidity reduction and measure chlorine residual |
| Accept-ability* | High | High to Moderate | High to Moderate | High | High to Moderate | High to moderate |
| Sustain-ability | High, unless fuel is scarce | High, probably | High, probably | High, probably | High | High, probably; limited data |
| Length of Treatment Time | Minutes to tens of minutes | Hours (full sun), days (clouds), not effective if no sun | Hours (full sun), days (part sun), not effective if no sun | Seconds to minutes, depending on water volume treated and reactor design | Tens of minutes | Tens of minutes |
*High is >75%; moderate is 50-75%