Continual Improvement through Investment, Training, and Creative Ideas
A DSRSD core value is to constantly increase efficiency even as we increase or maintain the level of service we provide to customers and the community. The projects below provide recent examples of increasing efficiency through prudent capital investments, training, and creative ideas that improve work processes.
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Good Ideas Save 60 Percent on Biosolids Disposal Cost
The District bought this used biosolids dredge on eBay for $23,000 and then spent $115,000 to refurbish it. No longer spending $90,000 a year on a contract dredging service, DSRSD recouped its investment in two years.
Situation: DSRSD was spending more than $330,000 a year to dispose of biosolids
Every summer, DSRSD dredges approximately 1200 dry tons of “biosolids” from one of its five, 15-foot-deep facultative sludge lagoons and plows the material 10 to 12 inches into the soil of an adjacent dedicated disposal site. The District is fortunate to own the 55 acres needed for these facilities. Land disposal is one of the least expensive ways to manage biosolids, and it’s friendly to the environment. Still, until 2009 the District was spending more than $330,000 annually on specialty contractors who had the necessary skills and equipment to do the job.
Solution: Implementing employee suggestions reduced costs by 60 percent
By implementing a series of creative employee ideas, the District has cut the annual cost of biosolids disposal by 60 percent, from $330,000 to $134,000. The process started in late 2008 when the great recession hit. As District revenue from developer fees plummeted, employees in every department brainstormed ways to reduce operating expenses. At the wastewater treatment facility, staff suggested having District personnel, rather than contractors, drive the tractors. They also wondered if it would be more cost effective to purchase, rather than rent, equipment used every year.
Tractors crisscross DSRSD’s Dedicated Land Disposal Site plowing biosolids, the organic material left at the end of wastewater treatment, into the soil.
Between 2009 and 2011, the District cut costs to $250,000 per year by using a combination of staff and temporary employees and purchasing some of the needed equipment. The revised budget still spent almost $90,000 on a contract dredging service. Staff kept looking for a used dredge to buy, but found none within an affordable shipping distance.
Then in 2012, employees spotted a dredge for sale on eBay, right down the road in San Jose. It needed some refurbishing but was still a good buy at $23,000, about 10 percent of the cost of a new dredge. Once it went into service in 2013, the cost of biosolids disposal fell again to about $160,000 per year.
In 2015, staff tested new ways to increase efficiency that cut costs further. For example, they set up marker flags to help tractor drivers precisely align each row. Previously drivers had used natural landmarks to eyeball their position. The flags allow them to use every inch of available space and cover the field in less time. They also tested driving faster to avoid over-saturating the soil, which increased the volume of biosolids that the field could absorb. The bottom line result: in 2015 biosolids disposal was completed six weeks early, saving enough in labor and equipment rentals to cut the annual cost to $134,000, 60 percent less than in 2008.
Future: Less Disposal, More Resource Recovery
The District recovers a renewable fuel, methane, from three anaerobic digesters to generate heat and electricity, reducing energy bills and greenhouse gas emissions.
Every day, as DSRSD treats 10 million gallons of wastewater, 82,500 gallons of wastewater solids are separated and conveyed into three anaerobic digesters. These huge airtight tanks operate like mechanical stomachs where enzymes and microorganisms break down the solids into stable compounds. As the bacteria break down the wastewater solids, they produce a valuable resource—methane. The District recovers this methane, blends it with natural gas, and feeds it to engine generators that produce all of the heat and half of the electricity used at the treatment plant.
In the future, biosolids management will evolve further from disposal to resource recovery. DSRSD is participating in the regional Bay Area Biosolids to Energy coalition, which is investigating technologies for recovering more of the energy from processed biosolids. The coalition is also investigating technologies that can recover water, carbon, and phosphorus from biosolids.