Abstract: A Method of treating sludge prior to dewatering by mixing with the sludge a cationic metal in the form of an iron or aluminum slat along with a cationic polymer. The addition of the iron or aluminum salt substantially reduces the amount of polymer required for acceptable dewatering, thusly significantly reducing the cost of the dewatering process. The method is enhanced by subjecting the prior digested sludge to mesophilic aeration prior to the cationic metal salt and polymer being added.

Abstract: A pathogen reduction system for a sludge treatment process that employees multiple reactors operating in a batch mode to reduce pathogen levels in the sludge while providing a continuous flow of pathogen reduced sludge to a digester. In addition, the present invention entails an efficient heat exchanger for heating and cooling the sludge being treated in the above process. In particular, the heat exchanger is of the counterflow type and includes a helical coil confined in an annular chamber for transmitting one media and wherein the helical coil is spaced so as to form another helical flow channel that is defined by the annular chamber and the helical coil itself. Consequentially, one media is directed through the helical coil while another media is directed through the flow channel that is defined in part by the helical coil.

Abstract: A pathogen reduction system for a sludge treatment process that employees multiple reactors operating in a batch mode to reduce pathogen levels in the sludge while providing a continuous flow of pathogen reduced sludge to a digester. In addition, the present invention entails an efficient heat exchanger for heating and cooling the sludge being treated in the above process. In particular, the heat exchanger is of the counterflow type and includes a helical coil confined in an annular chamber for transmitting one media and wherein the helical coil is spaced so as to form another helical flow channel that is defined by the annular chamber and the helical coil itself. Consequentially, one media is directed through the helical coil while another media is directed through the flow channel that is defined in part by the helical coil.

Abstract: The present invention comprises a wastewater treatment process wherein the waste activated sludge is digested to produce treated biosolids which are then directed to a dewatering facility that removes water from the treated biosolids. Before or during the dewatering process, both a low molecular weight polymer and a high molecular weight polymer are added to the treated biosolids. The addition of the two polymers of different molecular weights results in the treated biosolids coagulating and then forming flocs of biosolids that effectively drives water from the flocs and renders the flocs more susceptible to an efficient and effective dewatering process.

Abstract: A process for biologically removing nitrogen and other nutrients from wastewater using recycled activated sludge. A mixed liquor is formed from influent wastewater and recycled activated sludge and then treated in two successive nitrogen removal stages, each stage having an anoxic denitrification zone and an aerobic nitrification zone. The first nitrogen removal stage entails circulating the mixed liquor back and forth between the anoxic zone and the aerobic zone. The mixed liquor is then transferred to a final clarifier where activated sludge is separated from purified supernatant. To increase the NO.sub.x.sup.- reducing enzymatic activity of denitrification microorganisms, the activated sludge is retained in the final clarifier for a time period sufficient to permit adaptation of these microorganisms to a nitrate/nitrite-respiring metabolic pathway.