Table 9.
Efficacy and effectiveness of point-of-use technologies for low-income world households.
| Treatment process | Pathogen | Optimal log reductiona | Expected log reductionb | Diarrheal disease reduction (%)c |
|---|---|---|---|---|
| Ceramic filters | Bacteria | 6 | 2 | 63 (51–72) for candle filters 46 (29–59) for bowl filters |
| Viruses | 4 | 0.5 | ||
| Protozoa | 6 | 4 | ||
| Free chlorine | Bacteria | 6 | 3 | 37 (25–48) |
| Viruses | 6 | 3 | ||
| Protozoa | 5 | 3 | ||
| Coagulation/Chlorination | Bacteria | 9 | 7 | 31 (18–42) |
| Viruses | 6 | 2–4.5 | ||
| Protozoa | 5 | 3 | ||
| Biosand filtration | Bacteria | 3 | 1 | 47 (21–64) |
| Viruses | 3 | 0.5 | ||
| Protozoa | 4 | 2 | ||
| SODIS | Bacteria | 5.5 | 3 | 31 (26–37) |
| Viruses | 4 | 2 | ||
| Protozoa | 3 | 1 |
SODIS, Solar UV disinfection.
Data from multiple studies analyzed and summarized by Sobsey et al,113 Bielefeldt et al,203 WHO,36 Clasen et al,202 and data from additional references.23,123,204
Skilled operators using optimal conditions and practices (efficacy); log reduction: pretreatment minus post-treatment concentration of organisms (eg, 6 log = 99.999% removal).
Actual field practice by unskilled persons (effectiveness) depends on water quality, quality and age of filter or materials, following proper procedure, and other factors.
Summary estimates from published data vary with consistency and correct use of technique, integrity of techniques (eg, cracked filter), and other household sanitation measures; thus, these estimates represent effectiveness not efficacy, and real world not ideal conditions.