Select Link Consultancy Front Page Introduction to fouling problems Siltation problems Water resource management Chlorination solutions Biofouling monitoring Environmental Impact Assessment Expert witnesses & regulator approval services Short Period Intermittent Chlorination (SPIC) For years, FBS have proposed chlorine minimisation based on targeting critical areas of plant, phased reduction of dosing levels and reduction of the chlorination season by spat monitoring. At most power stations the last option was the main reduction technique that we could recommend. Dosing reduction is only feasible if the residual oxidant concentration is monitored continuously, and spat settlement monitored simultaneously to determine the efficacy of that concentration. Spat monitors readily detect settlement, but monitoring residual oxidant concentrations has proved to be a more difficult problem. Research using recently developed instruments, capable of continuously measuring residual oxidant in estuarine water, has shown that intermittent chlorination can be as effective an inhibitor of mussel growth as continuous chlorination, if the pulses are close coupled. Initial studies indicate that efficient control of mussel settlement could be achieved by rapidly pulsed, or short period intermittent chlorination, employing a symmetrical dosing regime (equal time periods of dosing on and off). This would lead to a 50% reduction in "chlorine" consumption and cost. However, since mussels close more rapidly upon exposure to a biocide than they reopen, it is possible to establish an equally effective asymmetrical dosing regime (ASPIC) with a longer period off than on, leading to even greater savings. Such regimes are site-specific.		We are now able to design and supply a monitoring system that will continuously measure the residual oxidant concentrations in each cooling water stream and provide a feedback signal. Incorporation of micro-processor control not only allows complete flexibility of the timing of the dosing regime, but also allows multiple level dosing, e.g. continuous dosing at 0.01 mg/l TRO for microfouling control with intermittent dosing at 0.2 mg/l TRO for macrofouling control. The system is self-testing since it can monitor the change between set points and react with an alarm if the new residual concentration is not achieved within a set time.
SPIC is a new concept in fouling control that may not be easily installed on all existing power stations. However, the substantial savings possible warrant its serious consideration.