The days of burying “cake” is coming to an end.
“Cake” is shorthand for the biomass solids created in the treatment of city wastewater.
While treated wastewater is sent into the San Joaquin River with a small percentage so far being recycled for landscape irrigation and construction uses, the biosolids have been hauled off and buried at a landfill.
A state mandate means the landfilling of biosolids will end throughout California this year.
And it won’t be cheap.
The Manteca City Council when they meet tonight at 6 p.m. are being asked to approve a three-year contract with Synagro West for $2,877,000. That comes out to $959,000 a year.
It will cost roughly $100 a ton to haul away and repurpose the biosolids based on Manteca generating 9,000 wet tons of “cake” annually.
The costs will be higher than burying the biosolids.
Compliance with Senate Bill 1383 that mandates diverting biosolids from landfills will be a contributing factor in what is anticipated to be a significant jump in Manteca wastewater rates expected to be imposed later this year
The monthly sewer rate hasn’t been raised in 14 years.
The treatment plant processes roughly 8 million gallons of wastewater daily from the cities of Manteca and Lathrop as well as the Oakwood Shores and Raymus Village neighborhoods.
The plant also receives seasonal discharges from Eckert’s Cold storage in Moffat Boulevard from the processing of bell peppers.
Synagro West has 1,000 plus wastewater treatment facilities and agricultural concerns as customers.
The firm handles 14 million tons of biosolids annually.
There are almost 250 treatment plants in California producing biosolids.
Wastewater goes through physical, chemical and biological processes to clean the water and remove the solids.
Biosolids may be applied directly to land if federal and state rules are followed.
Cal Recycle notes that 56% of the biosolids generated in California are land applied
Concerns about potential odors and public health impacts resulting from land application of biosolids have been expressed by members of the general public near such operations.
That said Best Management Practices (BMPs) have been established by state authorities in order to ensure odors are minimized and human health and the environment are protected.
Cal Recycle stresses BMPs include applying biosolids at agronomic loading rates, incorporating into soil, limiting soil pH, and restricting public access.
Biosolids and compost produced from biosolids are prohibited for use in organic agriculture under U.S. Department of Agriculture rules.
Composting is the second largest use of biosolids. Approximately 16 percent of biosolids are used at compost facilities for eventual use in agriculture, horticulture, and land reclamation.
Biosolids can be composted using a bulking agent such as wood chips or co-composted with green materials.
Cal Recycle indicates 19 percent of the biosolids generated in California are used as alternative daily cover (ADC) or final cover at some landfills. ADC is material used to cover and contain landfilled materials at the end of each day and is a critical part of vector control at landfills.
About 3 percent of the biosolids generated annually in the Golden State are disposed by treatment plant operators using nearby land. Since the process requires large swaths if land, it is not common.
About 2.5 percent of the state’s biosolids are incinerated. It is a process unlikely to expand given air quality regulations now make the process costly
Currently 13 percent of the state’s biosolids — including Manteca’s — are landfilled.
To contact Dennis Wyatt, email dwyatt@mantecabulletin.com
