JOURNAL OF COMPOSTING & ORGANICS RECYCLING
APRIL 2001

NO MORE MONEY DOWN THE DRAIN!

DIVERTING FOOD RESIDUALS FROM THE SEWER


By composting food residuals and removing kitchen garbage disposals, Del Mar Fairgrounds project sewer rate savings of $450,000 over the next ten years.

Nancy Strauss

MORE than three million persons visit the Del Mar Fairgrounds in Del Mar, California each year, attending the fair, National Horse Show and thoroughbred race meet. The 400 acres the fairgrounds - owned and operated by the 22nd District Agricultural Association - also include a horse boarding facility, golf driving range and tennis courts. The district has an extensive waste reduction program that began in 1985 with office paper recycling and now covers diversion of food residuals from going down the drain (see "The Last 10 Percent Is The Toughest," January 2000). It's all part of our staff's "zero waste or darn close" policy.
The largest amount of material diverted from the landfill in animal bedding. On an annual basis, more than 18,350 tons are composted. The straw bedding goes to the local mushroom farmer, and the shavings go to composting sites in the San Diego region. The district purchases finished compost from these same companies.
Preconsumer fruit and vegetable scraps are taken to the vermicomposting site in the middle of the racetrack. The worm castings are used on site for fertilizer. During the annual Del Mar Fair, all the food vendors participate in the food collection program. During the 20-day fair, approximately 40 tons of preconsumer food residuals are collected and hauled off site to local composting sites. Eighty-nine percent of the waste stream is diverted from the landfill and recycled or sent to composting.
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SEWER RATE REDUCTION
Richard Anthony of Richard Anthony Associates (RAA) in San Diego, California brought the possibility of a sewer rate reduction to our attention. From 1994 to 1998, Anthony was program coordinator for San Diego County's Wastewater Management Division. He was well aware of Del Mar's extensive recycling and food residuals diversion programs and believed we had a good chance of lowering our sewer rate.
"Redirecting the organics from the sewer to a composting facility results in less suspended solids at the wastewater treatment plant," explains Anthony. "This lowers plant costs and increases its capacity to process sewerage. The Federal Clean Water Act requires zero waste from sewer treatment plants and calls for the sharing of treatment and disposal costs based on the flow and strength of each generator's sewerage."
Diversion of food preparation residuals has allowed removal of garbage disposals from the kitchens and thus lower waste use. Since the sewer bill is based on a strength classification and water usage, removing the disposals saved water and reduced solids.
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TESTING FOR SEWER STRENGTH
A sewer sample was taken and tested from sewer strength. It looked promising and we approached the city of Del Mar with our concerns. The deputy general manager, Brad Gessner, negotiated an agreement with the city that stipulated if the district could prove the sewer strength was less than previously assigned, the city would adjust the rate appropriately and issue a refund for the previous 12 months and reassign the strength at the new level.
The difference in classification is several milligrams per liter for a shopping center (our choice) as opposed to a restaurant with a bar. The city required the district to complete ten separate tests during various times of the year. RAA supplied us with the documentation needed to challenge our sewer rates and the city agreed with the findings.
The results were overwhelming! They showed conclusively that the district was misclassified for sewer strength, which resulted in a 23 percent reduction in our sewer rate and refund of $45,000 for the previous 12 months and projected savings of $450,000 over the next ten years. Another benefit will be additional capacity at the municipal wastewater plant because of the diverted food residuals. This is just one more reason to make food residuals a part of any waste reduction program where food preparation takes place.

REDUCING SUSPENDED SOLIDS AND BIOCHEMICAL OXYGEN DEMAND FROM COMMERCIAL SEWERAGE

THE COUNTY of San Diego (California) Department of Public Works (DPW) manages and maintains four county sanitation districts that discharge wastewater to the San Diego Metropolitan Sewerage System (Metro) for treatment and biosolids disposal. Because Metro receives funding from the Federal Clean Water Program, all participating agencies must meet requirements for sewer service charges based on wastewater strength. To help customers with high strength wastewater, the county and the California Restaurant Association developed on educational program to help reduce flows, strengths and costs. The county and the association wanted to prove that source separation and a separate collection

program for food discards may be effective means of reducing wastewater strength and treatment, bakeries and other food handling businesses.

In June, 1997, a countywide pilot program was started to reduce strength and lower costs associated with waste water treatment. The program required routine maintenance of interceptors (large multistage grease traps) and source separating food discards from restaurants. In cooperation with the San Diego Chapter of the California Restaurant Association, the San Diego County Sanitation District conducted the pilot program through September, 1997. The Department of Public Works (DPW) staff sampled and analyzed effluents from restaurants and other high strength user groups.

DPW staff tested the wastewater during three intervals: Before the program began; After education and grease trap/interceptor maintenance was performed; and two weeks after the second sampling to obtain consistent values. Wastewater strengths were measured in terms of Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) levels in milligrams per liter of wastewater. District restaurants that participated in a preprocessed food separation and collection program reduced levels of BOD and TSS when proper waste management practices in the kitchen were implemented.

The test data provides exciting environmental and economic incentives with the application of a widespread food residuals diversion program from the waste water stream to composting . Sewer service charges for user groups listed by the state as high strength generators could then be reduced by removing the cause of strength and documenting the new levels of TSS and BOD. The federal and state requirements for a strength-based sewer service revenue program would be met and the new classifications would ensure fairness and equity.

-Richard Anthony
Richard Anthony Associates
raa@richardanthonyassociates.com

 


Sampling results for restaurant wastewater BOD and TSS.
 
State Standards
Sample 1
Sample 2
Sample 3
Restaurant
BOD
TSS
BOD
TSS
BOD
TSS
BOD
TSS

Applebees
1,000
600
1,380
302
200
148
508
148
Boston Market
1,000
600
280
52
200
152
29
177
Bonita Golf Club
1,000
600
820
195
200
215
570
299
KFC
1,000
600
1,820
248
600
248
580
150
Murietta's
1,000
600
1,540
520
590
160
600
411
 
Average:
1,168
236
358
185
457
237
 
Std:
616
171
216
45
242
115
 
Median:
1,380
248
200
160
570
177
 
Min:
280
52
200
148
29
148
 
Max:
1,820
520
600
248
600
411

Table compares the results of three sampling analysis for two fast food and three dine-in restaurants.