A modular integrated cooling and heating system for effluents and other uses involving mixing tanks connected in series, hot water supply pipes connected to each of the mixing tanks in order to convey to each mixing tank a portion of the hot water effluent from a power plant. Cooling water pipes are connected to each of said mixing tanks in order to deliver cooling water from a river or other source to said mixing tanks whereby hot and cooling water mixes in said first tank with the water mixture being continuously passed into said second tank for mixing with additional cooling water from a cooling water pipe. The number of stages or mixing tanks will vary depending upon the cooling capacity desired.In another embodiment of the invention, the hot water effluent conveyed to the first tank is not allowed to mix with the cooling water, but instead of the hot water effluent runs through convoluted piping in said first tank and is then discharged into said second tank with the remainder of the system being identical. This is the so-called co-generation modification utilizing hot effluent water which contains undesirable chemicals. In this co-generation modification the local water supplied by the water company or other utility is heated by contacting the hot walls of the convoluted piping and such heated water is then pumped in the uncontaminated state to homes or similar use.