Missouri River Treatment Plant Solids Handling

Burns & McDonnell is performing comprehensive wastewater treatment facilities master planning and design for improvements to the Metropolitan St. Louis Sewer District Missouri River Treatment Plant near Maryland Heights, Mo. The Missouri River Treatment Plant is currently designed for an average flow of 28 million gallons per day (MGD) and a peak flow of 80 MGD.

Treatment processes include screening, grit removal, preaeration, primary clarifiers, plastic media trickling filters, secondary clarifiers, effluent pumping, anaerobic digestion and belt filter presses for biosolids dewatering. The plant utilizes digester gas for generating electric power. The scope of master planning included projecting wastewater flows and characteristics, an assessment of regulatory issues that may affect plant requirements, and a capacity and condition assessment of all treatment unit processes. 

The project included a comprehensive assessment of the solids handling facilities. The current sludge treatment processes include pumping of combined primary and trickling filter solids to four anaerobic digesters, polymer sludge conditioning, and dewatering by belt filter presses. Dewatered biosolids are hauled to a central composting facility or land applied to reclamation sites. The assessment considered future process capacity requirements for expanding the trickling filter process, and replacement of the trickling filters with a new activated sludge process. In the case of expanding the trickling filters, various upgrades of the existing facilities are required including replacement of digester heating equipment (boilers and heat exchangers), replacement of the polymer feed system for sludge conditioning and replacement of the sludge conveyor system.

In the case of an activated sludge system, additional improvements are necessary including sludge thickening before digestion, conversion of a secondary digester to a primary digester to increase digester capacity, and installation of a third belt filter press. Alternatives were evaluated for sludge thickening including gravity belt thickeners and gravity thickeners.

Digester gas is used for fueling power generation equipment that reduces use of utility power. Various digester gas handling improvements were identified including a gas cleaning system for removal of siloxanes from the digester gas. Siloxanes form silicone deposits in the engines that result in frequent engine overhauls.

• Facility capacity analysis and master planning
• Expansion of capacity to 32 MGD
• Peak flow capacity expansion to 190 MGD
• New 190 MGD capacity preliminary treatment
• New 30 MG peak flow storage basins
• Odor control
• Existing plant rehabilitation
• Trickling filters
• Effluent pumping
• Anaerobic digestion
• Digester gas cleaning system
• Sludge dewatering
• SCADA upgrade
• Wetlands mitigation