Section 760. Bromochlorination

A. Disinfection by bromochlorination is accomplished with bromine chloride (BrCl) in a manner similar to chlorine disinfection. Bromine chloride is an equilibrium mixture of bromine and chlorine in both the gas and liquid states. The chemical is highly soluble in water and hydrolyzes to hypobromous (HOBr) and hydrochloric (HCL) acids. Due to the rapid decay of bromine chloride in wastewater, generally there will not be any measurable bromine chloride residuals in the final sewage effluents. Pure bromine chloride is a heavy, fuming, dark, red liquid which is about 20% disassociated into molecular bromine and chlorine.

B. Design. This disinfection process can be considered for treated effluents with BOD₅ and suspended solids concentrations of 30 mg/l or less. Prior documentation should be furnished which shows that adequate disinfection of a specific sewage effluent can be obtained with this process.

C. Dose control. Bromochlorination feed equipment capacity shall be based on degree of treatment, flow variations, and other uses in the treatment processes. For disinfection, the capacity shall be adequate to produce the control point residual required in the permit or certificate issued. The dosing capacity of this process for normal domestic sewage should usually be 80% of that recommended in the chlorine dosage Table 7.

1. Bromochlorination equipment and spare parts are essentially the same as similar requirements for chlorination.

2. Gas feeder systems may be used for feed rates less than 500 pounds per day. Direct liquid bromine chloride feed systems should be used for feed rates greater than 500 pounds per day.

D. Features. Where adequate heat is not provided by the vaporizer to prevent condensation, the use of auxiliary heating and insulation shall be provided as necessary.

1. Materials for piping and appurtenances shall be suitable for handling gas, pure liquid or solutions of bromine chloride as appropriate.

2. The required housing shall be the same as for chlorination, as per VOSH requirements.

3. An evaporator shall be provided for all gas feed systems. The equipment should be designed to minimize the time out of service for maintenance. A backup system shall be provided to ensure adequate disinfection for all discharges when the vaporizer is out of service for maintenance. The vaporizer system should provide superheated gas to the inlet of the vacuum-operated bromine chloride feeder.

E. Safety. The requirement for safety shall be the same as for chlorination and should be in accordance with VOSH requirements. A physical barrier shall be provided for the separation of storage areas if bromine chloride and chlorine chemical supply containers and gas cylinders are located in the same room.

F. Monitoring. Facilities shall be included for collecting samples for bromine chloride residual determinations at the five minute contact time control point and for pathogenic bacterial indicator organism determinations following the total contact period. There should be no readily detectable bromine residual within the final effluent.

1. As bromochlorination equipment represents new technology and limited performance data is available for these systems, an initial period of increased sampling frequency and testing requirements for pathogenic bacterial indicators, such as fecal coliform, may be required. The required initial testing program should take place over a period of one year or more under reasonable operating conditions with a minimum sampling frequency of at least once per week.

2. Disinfection of secondary or better quality effluent should consistently maintain a fecal coliform level below 200 per 100 milliliters of sample volume, or the allowable level contained in the certificate or permit issued, whichever is more restrictive.

3. Indicator organism test results should be correlated with other measurements at the time of sampling, including flow rate, effluent suspended solids, bromine dose rate, and residual measurements.

Historical Notes

Former 12VAC5-581-820 derived from Volume 18, Issue 10, eff. February 27, 2002; amended and adopted as 9VAC25-790-760, Virginia Register Volume 20, Issue 09, eff. February 12, 2004.

Statutory Authority

§ 62.1-44.19 of the Code of Virginia.