It is our opinion that excellent results in textile industry water recovery can be achieved by using activated carbon. The water coming from an efficient biological treatment is usually characterised by 120 – 160 mg/l residual C.O.D., and 60% colour removal (not perceptible after 1/20 dilution), residual suspended solids around 15 – 25 mg/l.
Before filtering through activated carbon, the water coming from the clarifier is filtered through sand (quartz filter) in order to remove the residual suspended solids. Now the water can be re-used, for example in the printing house for floor washing, frame washing, etc. In the dye house this water can be also re-used for rinsing of dark dyes, floor washing, tank washing etc.. The same use can be applied also to tanneries, paper and other types of industries.
Afterwards the water is filtered through activated carbon (activated carbon filter). The final result consists in an ulterior C.O.D. removal to 50 – 100 mg/l., a complete colour removal and reduction of the surfactants to 0.5 – 1.5 mg/l. Between the filters sodium hypochlorite could be dosed in order to get a water sterilisation; the residual of that chemical reagent is completely absorbed by the activated carbon.
Periodically the activated carbon must be replaced because it becomes saturated. Then it will be forwarded to special Companies which provide for its regeneration.