Application: Disinfection of tertiary treated effluent for re-use In many new residential developments, it is mandatory to install on-site treatment plants so that solid and aqueous waste is to very high standards. This especially applies to environmentally sensitive areas around the coast. Effluent is treated biologically and then polished with UF and RO membranes. Permeate is disinfected with chlorine dioxide for re-use as irrigation or washing water.
For small flow applications, the low capital and chemical running cost of the CDLa generator was the ideal choice. Dioxide Pacific was engaged to design, build and commission the generator and residual control system. The generator consists of two metering pumps dosing 3% sodium chlorite and 6% hydrochloric acid into a reactor. In the reactor a solution of 0.5% is produced which is safe to pump.
Chlorine dioxide solution is dosed through LDPE tube to the dosing point. Redox (ORP) and amperometric chlorine dioxide sensors are used to monitor residual. Control is from a ProMinent D1C monitor with PID control.
Dioxide Pacific provided the complete plant as a skid mounted assembly as shown.
Application: Disinfection of milk evaporator condensate Milk powder is produced from the evaporation of milk. The subsequent condensate water is usually very good quality with low conductivity and low TOC. However, it is warm and contains thermophilic bacteria which must be disinfected before it can be reused for wash water.
Chlorine dioxide has been successfully used in Australia in ten dairy sites for the treatment and re-use of condensate water. Condensate is captured in a large storage tank and circulated. The circulation water is dosed with chlorine dioxide to a residual of 0.4 ppm. Control of chlorine dioxide residual is achieved through ProMinent CDE2-mA-2ppm amperometric sensors and D1C monitors with PID control. The D1C monitor provides a pulse control signal to a BelloZon acid chlorite chlorine dioxide generator. The addition of acid from the acid-chlorite generation process causes a reduction in condensate pH which requires correction with caustic.
The system is supplied complete with acid and chlorite storage tanks, electrical and mechanical installation and preventative maintenance contract.
