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Skilled Operators Meet Record Demand for Recycled Water
Situation: During the summer of 2016, soaring demand for irrigation water pushed the limits of the sand filtration system at the Jeffrey G. Hansen Water Recycling Plant. Even with the addition of a sixth filter, which increased maximum output from 6.6 to 7.9 million gallons a day (MGD), the system ran at 87 to 96 percent of capacity for three months straight.
Solution: To meet the challenge, DSRSD’s plant operators stepped up their vigilance and efficiency at every point of the treatment process.
Photo: A contractor signals to the crane operator lowering a component of a new, sixth sand filter, which was added at the Jeffrey G. Hansen Water Recycling Plant in March 2016 to increase recycled water output.
Many Factors Can Limit Production
Recycled water plants are sized to meet peak summertime demand, but running at full throttle for weeks at a time is no small challenge. Grease and pollutants in wastewater can disrupt microbial processes during primary and secondary treatment. The resulting secondary effluent may not meet the stringent quality standards required for advanced tertiary treatment, reducing the amount of water that can be recycled.
Equipment breakdowns anywhere along the line can upset the tight production schedules. That, in turn, can make it impossible to refill the storage reservoirs that empty out each night during hot summer months irrigating parks, school grounds, and golf courses.
Bottom line: when demand is high, there is little margin for error.
Operators’ Experience Key to Success
The operators monitored, adjusted, and experimented to sustain optimal conditions for the wastewater plant’s microorganisms. They balanced production time with necessary preventative maintenance, such as continuously unclogging the sand filter airlifts (36 of them) and cleaning the 1,600 ultraviolet light bulbs that disinfect recycled water at the end of the process.
They began using the new sixth sand filter as soon as it was in place in May, before automated controls were installed. Operators ran the new filter in manual mode for most of the summer.
The plant has a separate microfiltration system that can produce another 2 million gallons of recycled water each day. Microfiltration is more costly than sand filtration and so is used primarily during cool seasons. But with demand soaring above the sand filters’ maximum capacity, operators ran the two systems in tandem on 27 days in June, July, and August.
As a result of extraordinary efforts by DSRSD operators, all customers received all the recycled water they wanted, all summer long.
Peak Recycling Capacity to Increase 70 Percent
An $18.2 million improvement project is underway to boost total recycling capacity by 70 percent, up to 16.2 MGD. The improvements will be ready in the summer of 2018. In the meantime, DSRSD’s plant operators will keep relying on their skill and efficiency to meet the Tri-Valley’s growing use of recycled water irrigation.
Chart: Customer demand for recycled water jumped to new highs during the summer of 2016 (blue line) as new irrigation sites came online in Pleasanton, Dublin, and San Ramon.
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