Mixer eliminates thermal stratification

Problem

Operators at the Spanaway (Wash.) Water Co. discovered thermal stratification inside a 127-foot steel standpipe after noticing heavy condensation each morning at the bottom 30 feet. Probes installed at 20-foot intervals in the tank measured temperature differences as great as 19 degrees F. Water samples indicated 0.7 mg/L chlorine residual at the bottom of the tank and almost zero residual at the top. Poor-quality water entering the distribution system often triggered taste and odor complaints.

Solution

Operators installed a single Water Mixer from PAX Water Technologies in less than a day and without a crane or heavy equipment. Every hour, a powerful jet blended a foot of stratified water. The unit completely mixed the water column in seven days, and lowered the upper layer temperature from 66 degrees F to below 61 degrees F. Grab samples showed chlorine residual at the top of the tank increased from zero to 0.31 mg/L.

Result: "Consistency in water quality is the key to customer satisfaction," says water programs manager Tim Tayne. "This also ensures the water always meets drinking water standards, even during high demand." 866/729-6493; www.paxwater.com

Cover and liner restores reservoir

Problem

Tears in the cover and liner of the 12-million-gallon reservoir at Bethlehem, Pa., and water pooling on the cover convinced city officials to decommission the 30-year-old basin. The replacement project for the reservoir went out to bid.

Solution

MPC Containment won the contract. Workers designed, fabricated and installed a 150,000-square-foot 45-mil CSPE black/black liner and identical black/blue cover using materials from Burke Industries. They removed silt buildup and trees and attachments to a pump house and vertical structure at one end of the reservoir. The company also recommended enhancement tubes to direct standing water to the nearest trough for expulsion by the pumping and double-Y trough system.

Result: The city received a fully functional water reservoir. 800/621-0146; www.mpccontainment.com

Dewatering improves solids handling

Problem

The 8 mgd Bluebonnet Water Supply Corp. Water Treatment Plant in Temple, Texas, generated a worst-case 106 million gallons of spent backwash water and clarifier sludge annually, storing it in three concrete lagoons. Solids in the settling lagoon never dried sufficiently to permit effective removal. Handling the monthly average waste of 266,000 gpd sludge and paying a hauler to transport it was a considerable operational effort and expense for the facility.

Solution

Bluebonnet added three modified sludge collection basins with vacuum transport units, two lift stations, and the Poly-Mate polymer system and Sludge-Mate dewatering containers from Flo-Trend Systems. The three basins are active, having material settling in the bottom of them to a depth of no more than 1 foot before the sludge is transferred. When the sludge collection system activates, 19,600 pounds of solids flow by gravity to the first lift station, where the material is dewatered to 15 percent solid cake. Filtrate drains to the second lift station and returns where it is returned to the headworks of the plant.

Result: Chief of operations Damon Boniface and staff stay ahead of sludge production and control disposal costs. 800/762-9893; www.flotrend.com