TABLE 1.

Comparison of wastewater reclamation facilities sampled for indicator organisms and pathogens in this study

FacilityAvg capacity (m3 · s−1)Biological treatmentChemical use prior to filtrationFilter composition (depth, m)Backwash frequency (h)Type of disinfection
A0.04Activated sludgeNoneFabric (0.02)24 to 72Chloraminesa
B0.4Activated sludgeChlorineSand (0.3)Automatic (daily)Chloraminesa
C0.4Activated sludgeCationic polyelectrolyteAnthracite (1.2)48Chloraminesa
D0.7Activated sludgeNoneAnthracite (0.8), sand (0.25)48 to 168Chloramines
E0.08NitrificationNoneSand (1.2), upflowContinuousUltraviolet light
F0.13Biological nutrient removalNone (alum added to secondary clarifier)Anthracite (0.6), sand (1.2)48 to 168Chlorine
  • a Chloramines are formed due to the reaction of chlorine with residual ammonia.