Grease Collection- III

Grease Collection and Retention
• Based on the Clean Water Act and
• closures of the public beaches due to the sewer contamination of the beaches,
• several court cases have forced an overhaul of the practices of the restaurant facilities and eateries in southern California.
• Financial cost of the street public sewer cleaning process,
• major clog sewage treatment plant,
• or a beach closure is enormous.

The overflow of sewer into the public storm drain system is a paramount issue to avoid in any public works. The presence of grease particulates in the sewer system has greatly increased this probability. Although the best operation management practices within restaurants are in place, they are hard to monitor and comply. Lack of staffing is the primary cause. However, the Authority Having Jurisdictions will have a great opportunity in scrutinizing the engineered plans and to insure proper design practices are in place. Along with many other inspection, the designed plans are part of the environmentally correct restaurant, or food manufacturing plant.

A typical sewage treatment plant contains several processes. Various forms of basic screening, filtration, settling chambers, clarifiers, and chemical additives are some of the processes. Grease particulates at lower temperature coagulate and become a clogging mechanism in nearly every one of the stages of sewage treatment. The organic properties of the grease particles make an excellent meal for bug growth within the plant, hence increasing the BOD levels and increasing the cost of the treatment plant. Some estimates are up to 80 cents per gallon of treatment. Sudden massive dosage of food in the sewage treatment plant induces the bugs to eat the food at rapid rate and not reproduce enough for the next cycle. At this point, plant operator must introduce cultured bugs into the system for its natural process. Each Jar of bugs cost near $400.00.

Case history: In Orange County California, Grand Jury (2000-2001) reviewed 35 wastewater facilities with near 12,000 miles of sewer lines and near 7000 restaurants. The purpose of the review was the possible sanitary sewer overflow events resulting in beach closures. The following was the result of that review:
“Restaurant generally dispose of cooking grease/oil in the following three ways:
1. Grease traps- These are small devices hooked directly to the outgoing drains of sinks and dishwashers and are located inside the restaurant. Beause they hold small quantities of captured grease, these traps must be emptied and cleaned on a regular basis, and the grease properly discarded to prevent grease overflow into the sewer system.
2. Grease Interceptors- Interceptors are large underground devices usually located out the restaurant and connected to the restaurant’s outgoing sewer drainage system. These large tanks have heavy man-hole-like covers that are difficult to access for inspection. When full, they must be emptied and cleaned by private waste pickup and disposal companies.
3. Large covered barrels- Barrels in which higher quality cooking grease is placed are kept covered and then collected by commercial companies who sell it for industrial reuse. These barrels are placed outside the restaurant. They are easily accessible and are usually not a contributing factor to the problem, unless they are accidentally spilled and the contents enter sewer or storm drain”

Case History: Cookie factory in San Marcos California: The night shift cleaning of the facility would cause a large magnitude of sugar and sweets to flood the treatment plant in short period of time. The enzyme eating bugs would feed themselves to extinction. Therefore, the facility had to replenish the bugs at $400.00 per jar ($1000.00 per night) to renew the bugs life cycle within the facility. Solution a large 10,000 gallon dilution plant was used for the interceptor to accept the dilute the night shift sewage with day sewage, and hence the bugs life would be in equilibrium.

Localized retention and capture of the grease at the source (the restaurants, factories, etc.) greatly enhances the entire system, and the cost becomes a component of the restaurant cost of operation as oppose to the general public tax payer supporting the maintenance of sewer piping and infra structures or the treatment plant.

Unfortunately, within all counties across the country, there is no consensus on what kitchen equipment should be grease sewer piping. There is some equipment that is not in question, i.e. the prep sink, the scullery sink. However, the verdict is not unanimous on several others. The controversial ones are the floor drains, the mop sink, the dishwasher, and the sink with the garbage disposal. The theory is that any water/sewer mixture that contains solid particles or detergent chemicals must not go to interceptor/trap. The detergent by its nature creates bubbles and attracts the grease particles and through lighter weight and its buoyancy, which bypasses the retention chamber freely. The solid particles clog the system and create havoc within the chamber. Floor drain and floor sinks have never been reasoned within many jurisdictions.

One of the properties of the grease is the viscosity variations with temperature as well as the phase change of liquid to solid at room or lower temperature. This issue amplifies in colder climate or long distance traveling of the grease sewer piping. The change in viscosity and thus its solidification increase the chance of roto rooter house calls. Burial of the piping below the freeze point of the finished floor plus providing electric heating jackets for the piping greatly enhances the flow of the grease sewer piping as well insures the uniformity in the viscosity throughout the year.

The most culprit piece of equipment in the kitchen has been identifies as the pre-rinse prior to the dishwasher. This accounts for nearly high percent of the grease content of the kitchen. Most other fixtures are incidental grease load and are not frequent. A local treatment or collection of grease to the pre-rinse may solve overall grease collection process.