The HUBER STRAINPRESS® has helped Napa Sanitation District maximize its investment in its fats, oils, and grease receiving system by improving operations, ensuring the protection of downstream components, and enhancing the production of a valuable, revenue generating asset.
By Mark Egan
Napa Sanitation District, located in Napa Valley, CA, provides wastewater collection, treatment and disposal services to the residents and businesses in the City of Napa and surrounding unincorporated areas of Napa County. As an independent special district, Napa Sanitation District is governed by a five-member Board of Directors, comprising of three elected officials from the City of Napa and Napa County and two public appointees. Their mission is to collect, treat, beneficially reuse, and dispose of wastewater in an effective and economical manner that respects the environment, maintains the public’s health, and meets or exceeds all local, state, and Federal regulations.
Napa Sanitation District struggled for a long time with a bucket type strainer as the screening technology for their fats, oils, and grease (FOG) receiving and injection system. Not only was trash passed through the bucket an issue for efficiency, but it was also a safety hazard. “I got a sharp stick in the hand from a sewing needle when clearing out the clogged bucket strainer. It’s a huge safety risk because of the environment you’re working in—with all sorts of waste, including heavy restaurant waste and waste from a chicken processing plant entering the stream. Each time we must clear out the bucket, we risk an injury and infection,” says Dusty Maynard, Operator III.
Napa saw all sorts of debris land in their FOG bucket strainer, but not all of it was getting screened out before the FOG moved into the digester. Non-digestible debris was showing up downstream of the strainer, which is not acceptable if the FOG system is expected to work efficiently. The stream must be cleaned out ahead of reaching the digester because it takes up valuable space, and it also has the potential to cause damage. The bucket strainer clogged frequently, causing a halt in the process that allowed operators to manually unplug it. This is nasty, hazardous work. The odor is persistent and lasting and the waste stains ruin clothing. It is truly a foul experience.
Stopping the process to unplug the strainer is time-consuming. Two to three times a day, operators must manually get the strainer back into working order. This adds up to approximately eight-man hours per week. Those are eight-man hours that operators could spend on more productive activities. “Basically, we must make sure that the flow into the digester is clear of debris. The more efficiently we can do that process, the better off we are in respect to cost and safety,” says Maynard. “Anytime we must stop everything for a fix, it costs us. Even though the FOG system generates revenue in the end, it makes no sense to burn up the valuable time of our operators on clearing out clogs.”
The big issue with FOG receiving, though, is the never knowing what kind of trash is mixed in the haul. Grease traps are notorious for collecting all types of debris, some of which can be very hazardous. “While the FOG system is a tremendous asset to us, it can create issues for us if the screening technology used with it doesn’t adequately perform. And that is what we were struggling with in using the manual bucket type debris strainers as the screening component of our FOG system,” says Maynard.
Images courtesy of HUBER.
From Dinner Forks to Dishwashing Gloves
Because FOG injection enhances digester performance, a FOG receiving and injection system was a desirable one to implement. The increased production of methane gas ultimately increases the amount of energy the process can produce. In the end, this internally produced methane gas generates energy that offsets operations costs and creates new revenue in the sale of excess methane gas.
They needed to replace a basket strainer that removed debris from their septage hauling. The basket strainer was inefficient, required significant maintenance, could not be automated, and posed significant health and safety risks. They selected a strain press to solve these problems.
Comments Maynard, “When we saw the STRAINPRESS® pilot at the nearby Walnut Creek Wastewater Treatment Facility, we knew that we wanted to implement it. Instead of HUBER taking the pilot component back to its headquarters, we simply had them bring it to our site.” So, Maynard reached out to the HUBER California representative, Ryan Spanton with Goble Sampson.
HUBER Technology serves the municipal and industrial wastewater treatment market with high quality liquid-solid separation technology. HUBER Technology offers the complete chain of screening, grit, and sludge handling processes. The company is an original source manufacturer specializing in stainless steel fabrication of technologies for water and wastewater with proven experience and expertise with more than 40,000 installations worldwide.
The STRAINPRESS® is a horizontal pipe-shaped coarse material separator that consists of inlet and driving zone, screening and press zone, and finally a discharge section with a conical pressure regulating device. The coarse material is separated continuously under pressure and periodical cleaning of the screening zone by backwashing is not required.
The Perfect Choice for FOG System
Once Napa Sanitation District decided upon the solution, implementation was in a matter of months. Training was minimal for operators and septage users and has been a dramatic increase in efficiency and decrease in O&M and health and safety concerns.
The HUBER STRAINPRESS® has helped Napa Sanitation District maximize its investment in its FOG receiving system by improving operations, ensuring the protection of downstream components, and enhancing the production of a valuable, revenue generating asset. The HUBER STRAINPRESS® integrates perfectly into the FOG system to be an integral part of its success. Says Maynard, “The HUBER STRAINPRESS® has processed a huge amount of waste without a single hitch. Because there are no clogs to manually clear, we never have to touch the waste and avoid any safety risks from doing so. And the bonus is that we also avoid mess and odor!”
According to Maynard, adding the STRAINPRESS® completely transformed their operational experience, giving them results that optimized their FOG receiving program. “HUBER’s STRAINPRESS® stops all the debris. We don’t see debris beyond it so we can be confident that clean flow is entering the digester. Since day one, the HUBER STRAINPRESS® has done a wonderful job.” | WA
Mark Egan is Facilities Maintenance Supervisor at Napa Sanitation District. For more information on HUBER, call (704) 949-1010 or e-mail [email protected].