The existing facility initial construction was completed in 1941. It consisted of the main control building, 2 circular secondary clarifiers, 2 3 pass aerator basins, 3 rectangular primary clarifiers, 4 anaerobic digesters and sludge drying beds. Currently, all processes are still in service except the primary clarifiers and the drying beds.
The first plant expansion was completed in 1956. Design average flow was 20MGD. The expansion consisted of a raw sewage pump station, grit removal detritors with comminutors and parshall flume and chlorine supply facility. 2 additional circular secondary clarifiers, 3 additional rectangular primary clarifiers, 2 additional 3 pass aerator basins, a blower control building with positive displacement blowers (3) and vacuum filter presses. 2 additional anaerobic sludge digesters were also added.
In 1977 a advance waste treatment facility(AWT) was completed consisting of 5 rapid sand mutli media filters, backwash surge tank, 2 additional rectangular secondary clarifiers, additional blowers and raw sewage pump upgrades to increase design flow to 24MGD.
An EPA grant funded a project begun in 1983 that focused mainly on sludge processing and improving the existing land application/management program. It included new return activated sludge (RAS) pumps, 4 filter belt presses, semi tractors and tankers (6) and land application vehicles for both liquid and dried sludge (5). Additional waste pumps, transfer pumps and various other process pumps were included, as well as 4 new centrifugal blowers. 2 centrifuges were included for waste activated sludge (WAS) thickening prior to digestion.
A new AWT pump station was completed in 1996 which consisted of 3 200 hp submersible pumps to replace the 3 screw pumps which were part of the original 1976 construction.
A 42” diversion line with an additional outfall (#30a) was completed in 1998 at the AWT to bypass filters and maintain effluent flow during high river levels/flood conditions. New weirs on the ‘old’ (1941) secondary clarifiers and the rectangular (1976) clarifiers were included as well as a new operable main discharge sluice gate on the final outfall (#21a).
Phase I and Phase II projects were started in 2000 and were undertaken consecutively to replace, improve and repair much existing equipment from the original 1941 & 1956 projects. Phase I focused mainly on the ‘back end’ of the plant and included 2 circular primary clarifiers to replace all the existing 1941 & 1956 rectangular ones. A new primary pumping facility/control building and a flow control basin to modulate the primary effluent/ return activated sludge (RAS) ratio/mix to the aerators were also added. 2 new belt presses replaced 3 of the 4 original belt presses from the 1983 project. A complete sludge conveyance facility was constructed to transfer the dewatered sludge from the presses to trucks for landfill transport. The 2 anaerobic digesters from the 1956 project were upgraded and repaired with draft tube mixers retrofitted for each(4 per). An existing, unused basin was converted to a side stream treatment (SST) process and a septic receiving station (SRU) was built for domestic haulers to discharge to.
Phase II was completed in 2008 and included 2 main points of focus – an improved head works and AWT facility. The head works improvements consisted of 2 fine screens with screening washer/compactors, 4 new raw sewage pumps(3@ 20”/20 MGD & 1 @16”/10 MGD), a new pre cast parshall flume for raw flow measurement and a new grit removal facility. Cosmetic improvements on the existing pump station, originally built in 1956, were completed as well as totally new electric service and new process control electronics. The grit facility consisted of 2 head cells for grit removal from the raw stream, grit pumps, and dewatering equipment. The AWT improvements focused on media replacement from multi media to mono media. Air grids were installed below the media beds to improve backwashing. New valves, actuators, controls & blowers were also installed.
In 2011,MSD under took 2 improvement projects. CSO 18 was relocated & renamed CSO 37. The CSO was moved from the north side of White River across from the Treatment Facility to the south side of the river on the grounds of the Facility. Also, the Jakes Creek Lift Station was improved and a 2.5 million gallon equalization tank was erected for excess storm flow. Both of these projects are completed and online.