The Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) established
guidelines for Cryptosporidium inactivation credit with ozonation. In order to meet
these requirements, drinking water utilities may have to employ a bromate mitigation
technique to comply with the Stage 1 Disinfectant/Disinfection Byproducts Rule,
which established a maximum contaminant level (MCL) of 10 µg/L for bromate. In
2000, the Southern Nevada Water Authority (SNWA) and Black & Veatch initiated pilot plant
studies investigating the effect of various pretreatment strategies to control bromate
formation. Results showed that the use of prechlorine followed by preammonia
reduced bromate formation by 65-95% compared to no mitigation technique. The
process controls bromate formation by preoxidizing bromide to hypobromous acid,
which then reacts with ammonia to form bromamine. Bromamines sequester the
bromide through the ozone contactor reducing the formation of bromate. In the
following years, ammonia feed facilities were designed and constructed to implement
this process at full-scale. In 2006, the SNWA began using the pretreatment technique
at the 300 MGD River Mountains Water Treatment Facility. A 90-day evaluation
demonstrated that the chlorine-ammonia (Cl2-NH3) process could maintain bromate concentrations below the MCL. In addition, the Cl2-NH3 process allowed a threefold
increase in CT while still meeting the MCL. This pretreatment technique offers
utilities another pretreatment alternative to control the formation of bromate. Includes 6 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 160 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 11/01/2007 |
