Project Details

The treatment system at the WWTP consisted of pressurized sand filtration, biological cyanide and ammonia oxidation with rotating biological contactors (RBCs), followed by tertiary pressurized sand filtration prior to discharge. The main treatment portion of the facility, the RBC system, was original to the 1983 plant construction, with only minor improvements. Increased maintenance, lack of replacement parts, process obsolescence, and age of equipment led SURF to examine alternative processes and equipment to accomplish the current tasks of the existing RBCs.

A new treatment system, a moving bed biological reactor (MBBR) process was constructed to replace the RBCs. The MBBR process is an innovative biological wastewater treatment system which includes media to allow both attached biological growth and suspended growth to occur. Having both attached growth and suspended growth microbes allows removal of pollutants within the wastewater stream prior to discharge with a much lower footprint than the RBC system. Moreover, the MBBR system provides adaptability for the possibility of future nutrient removal requirements. Once the new treatment system is fully operational, all of the RBCs can be demolished allowing a much cleaner site for the WWTP. Treatment of the underground water and GGTF tailing water is essential for protection of Gold Run Creek, where discharge occurs, and is important for overall protection of the environment from pollutants. This treatment system allows SURF to meet required discharge permit limits in the surface water discharge permit regulated by the state of South Dakota Department of Agriculture and Natural Resources.

A Preliminary Engineering Report was prepared, examining alternative processes and equipment to accomplish the tasks of the RBCs. In that report, a moving bed biological reactor (MBBR) system was selected to replace the RBCs. The MBBR process is an innovative biological wastewater treatment system that provides highly effective treatment with a small footprint for replacing the RBCs. It is an industry known process with several different equipment suppliers having experience treating wastewater similar to SURF’s. A World Water Works MBBR system was constructed for SURF.

The MBBR treatment system is a fixed film process used for treatment of various wastewaters. The uniqueness of this type of system from other fixed film processes is that the biofilm is mobile throughout the basins. The MBBR acts as a fixed film process due to biofilm carriers that are mobile throughout the treatment basin. The biofilm carriers are retained within the basin at all times by use of a retention screen or sieve at the inlet and outlet of the reactors. The media used for the SURF MBBR is HDPE, a plastic material with a high surface area on which the biofilm grows and microbial degradation of pollutants occurs.

The MBBR treatment system constructed for SURF is a two train, single stage system, with the ability to operate as a two stage process during high load conditions. Mixing and aeration is provided by a blower system through aeration piping and a coarse bubble aeration system within the basin. Blowers are located in a new Blower Building. The SURF MBBR system removes ammonia and continues to remove cyanide as needed. Wasting of biosolids is not required in the SURF MBBR because biomass sloughed from the carrier exits through the waste stream. For the SURF WWTP, sloughed biosolids are removed by the final sand filtration system.