Two-stage digestion upgrade

Problem

A major expansion at the London (Ohio) Wastewater Treatment Plant would raise the design capacity to 5.8 mgd and include a biosolids processing facility to replace conventional digesters. The city wanted a system that improved reliability and ran automatically.

 

Solution

Design engineer CH2M HILL selected the two-phase Class A system with ATP/ESD process from CB&I to handle 34,000 gpd in 10 to 12 batches. The reactor in the anoxic thermophilic process (ATP) acidifies the feed materials and maintains 149 degrees F for one hour to reduce pathogens.

Thickened primary and waste activated sludge are blended, then heated with a hot water to sludge exchanger as well as a heat recovery system that cools the reactor sludge before feeding the 450,000-gallon, mesophilic, egg-shaped digester. The system eliminates heating of the digester which retains the material for 13 days at 98.6 degrees. The process is U.S. EPA-certified, so no testing was required. Class A biosolids were achieved within 45 days of startup.

 

Result

The automated system reduces digester retention time, produces Class A biosolids, and allows unmanned operation on weeknights and weekends. 815/439-4015; www.cbi.com.

 

Fabric structures provide protection

Problem

The fiberglass enclosure for a clarifier tank at the Leadville (Colo.) Wastewater Treatment Plant had structural faults. The manufacturer was no longer in business, and other fiberglass structure companies did not make the required enclosure. Officials hired building contractor Duran & Lucero in Leadville to research options.

 

Solution

The company chose a 75- by 70-foot-long Hercules truss arch building from Clear- Span Fabric Structures. The triple-galvanized steel tubing withstands 90 mph winds and snow loads of 90 pounds per square foot. The design, with no internal columns, has ample height for a catwalk across the middle and a door on each end of the building. The noncorrosive, sound-absorbing white fabric cover admits natural light. The fabric’s translucent and reflective qualities stabilize indoor temperatures so that the building stays cooler in the summer and warmer in the winter.

 

Result

The facility has a durable structure that withstands the harsh Colorado climate. 866/643-1010; www.clearspan.com.

 

Modular fiberglass shelters install easily

Problem

The engineering firm representing the Ashland (Pa.) Wastewater Treatment Plant had to enclose a fluidized-bed bioreactor developed by Envirogen Technologies. The design involved a filtration system with multiple pipes.

 

Solution

The engineers selected RM Products to design an insulated structure tailored to the filtration system. The modular building was taller than the standard 9-foot height. Besides a service door, the front face had a custom entrance with lift door. It and a second larger lift door at the rear enabled workers to access equipment on either end of the building or bring equipment in without dismantling the piping. Intake and exhaust fans, heat and lighting were included.

 

Result

The contractor assembled the unit on site with little assistance from RM’s technical team. 800/363-0867; www.rmfiberglass.com.