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The system's inherent enhanced treatability, in conjunction with a high level of mixed-liquor suspended solids(MLSS) (4,000-6,000 ppm) NOTES and quiescent settling, promotes the growth of facultative organisms that achieve additional breakdown of the waste by utilizing some of the chemically bound oxygen present in the mined liquor. The elevated temperature increases the biological metabolism of these newly generated floc colonies,which also require lower oxygen concentrations to remain aerobic.Most conventional treatment plants generate a crude refrigeration cycle during the aeration process,thus negating this effect and lowering the overall plant efficiency. In other systems using similar processes, denitrification of the sludge may occur in the settling tanks, taus ng sludge flotation and possible transfer to the next stage. Mechanical skimmers are detrimental to proper processing, as they prevent proper settling and solids will be discharged to the chlorine contact chamber. With the ACT system, floating solids which are not weired back during the aeration-to-clarifier transfer cycle are trapped on the top three inches of supernatant, which is not passed to the chlorine contact chamber, but is returned to the aeration tank by the clarifier sludge return pump which empties the clarifier tank each cycle. The rate of sludge buildup is minimal, as it is balanced by the rate of sludge destruction through repeated recycling from the clarifier, chlo- rine contact chamber, and the final filters back through the aeration cycle. A perfect balance between sludge generation and sludge destruction is possible in theory, but cannot be achieved from a practical stand- point. As a result, a plant operating at or near maximum capacity, which is producing a highly polished effluent,will require that excess sludge be wasted at intervals of from one to three years. The actual interval for sludge wasting or removal depends upon system opera- tor's skill,plant maintenance,and influent characteristics. Chlorination is accomplished by one of the following means: Diluted liquid chlorine is injected into the clarifier/chlorine contact chamber transfer line using a demand-type injection system, or, in cases of larger systems and where proper safety conditions can be met, chlo- rine gas may be injected into the transfer line. In both cases, clarified supernatant is chlorinated prior to entering the chlorine contact chamher; where the 70-minute settling period allows complete reaction to the chlorine; thus, there is no effluent bleedthrough as occurs in flowthrough-type systems. The chlorine contact chamber may be discharged as secondary efflu- ent, pumped through either a multimedia pressure filter or a con- tinuous-backwash filter such as the DynaSand by Parkson.Any min- ute particles backwashed or rejected from the filters are returned to either the aeration or buffer tank for recycling. 4