A system for controlling, reducing and/or mitigating the amount of liquid waste from, or derived from, a fuel-fired furnace and/or boiler, the system comprising: a fuel-fired furnace and/or boiler that burns at least one fuel to generate heat and flue, or combustion, gases; at least one particulate control device (110, 112), wherein the particulate control device (110, 112) is located downstream of the furnace and/or boiler and is operatively connected to same; one or more wet flue gas desulfurization units, wherein at least one of the one or more wet flue gas desulfurization units is located downstream of the at least one particulate control device (110, 112) and is operatively connected to same; and at least one spray drying device that receives and dries a liquid waste and/or liquid waste stream containing a level of total suspended solids content in the range of 1 percent by weight to 60 percent by weight and a total dissolved solids content of 2,500 ppm to 250,000 ppm, wherein the at least one spray drying device is located in a flue gas slipstream, wherein the flue gas slipstream receives a portion of the heat-laden flue, or combustion, gases from the fuel-fired furnace and/or boiler and wherein the at least one spray drying device is operatively connected at a first upstream end to at least one of the one or more wet flue gas desulfurization units and receives either the complete liquid waste and/or liquid waste stream, or at least a portion of the liquid waste and/or liquid waste stream, from at least one of the one or more wet flue gas desulfurization units, and is further operatively connected at a second downstream end to one or more injection points (122, 124, 126, 128, 130, 132) in a main flue gas stream generated by the fuel-fired furnace and/or boiler and provides either a complete dried waste and/or dried waste stream, or at least a portion of the dried waste and/or dried waste stream to the main flue gas stream, wherein the complete liquid waste and/or liquid waste stream, or a portion of the liquid waste and/or liquid waste stream is supplied to the at least one spray drying device without any pre-treatment process or step to remove any portion of the suspended solids contained therein; wherein the at least one spray drying device controls, reduces and/or mitigates the volume of liquid waste and/or liquid waste stream from at least one of the one or more wet flue gas desulfurization units via the use of at least a portion of the flue, or combustion, gases generated from the furnace and/or boiler and to provide the dried waste and/or dried waste stream to one or more injection points (122, 124, 126, 128, 130, 132) in the main flue gas stream. a fuel-fired furnace and/or boiler that burns at least one fuel to generate heat and flue, or combustion, gases; at least one particulate control device (110, 112), wherein the particulate control device (110, 112) is located downstream of the furnace and/or boiler and is operatively connected to same; one or more wet flue gas desulfurization units, wherein at least one of the one or more wet flue gas desulfurization units is located downstream of the at least one particulate control device (110, 112) and is operatively connected to same; and at least one spray drying device that receives and dries a liquid waste and/or liquid waste stream containing a level of total suspended solids content in the range of 1 percent by weight to 60 percent by weight and a total dissolved solids content of 2,500 ppm to 250,000 ppm, wherein the at least one spray drying device is located in a flue gas slipstream, wherein the flue gas slipstream receives a portion of the heat-laden flue, or combustion, gases from the fuel-fired furnace and/or boiler and wherein the at least one spray drying device is operatively connected at a first upstream end to at least one of the one or more wet flue gas desulfurization units and receives either the complete liquid waste and/or liquid waste stream, or at least a portion of the liquid waste and/or liquid waste stream, from at least one of the one or more wet flue gas desulfurization units, and is further operatively connected at a second downstream end to one or more injection points (122, 124, 126, 128, 130, 132) in a main flue gas stream generated by the fuel-fired furnace and/or boiler and provides either a complete dried waste and/or dried waste stream, or at least a portion of the dried waste and/or dried waste stream to the main flue gas stream, wherein the complete liquid waste and/or liquid waste stream, or a portion of the liquid waste and/or liquid waste stream is supplied to the at least one spray drying device without any pre-treatment process or step to remove any portion of the suspended solids contained therein; wherein the at least one spray drying device controls, reduces and/or mitigates the volume of liquid waste and/or liquid waste stream from at least one of the one or more wet flue gas desulfurization units via the use of at least a portion of the flue, or combustion, gases generated from the furnace and/or boiler and to provide the dried waste and/or dried waste stream to one or more injection points (122, 124, 126, 128, 130, 132) in the main flue gas stream.