Guide to Interceptors Presented by Why do we

Guide to Interceptors Presented by

Why do we need GREASE Interceptors? • The purpose of a grease interceptor is to intercept and collect free -floating fats, oils, and grease (FOG) from a commercial or institutional kitchen’s wastewater discharge. • At home, it's easy enough to dispose of fats, oils, and grease (FOG) properly: just pour it into an empty jar or can and put it in the trash. But in larger-scale establishments the FOG that these kitchens need to dispose of is far greater in volume and frequency, requiring a specialized device to ensure pipes and the things they connect to remain functional and safe.

FATS, OILS, and GREASE • When fats, oils, and grease (FOG) cool at normal temperatures, they solidify in pipes. When this happens, blockages can form in the sewer pipes, eventually causing backups in the collection system called Sanitary Sewer Overflows (SSO’s). • Any location with long plumbing runs to the sewer collections system inside a large building, such as a mall, hospital, or restaurant are in danger of creating blockages in the pipes which could lead to backups, fines, and perhaps even downtime as the internal plumbing is repaired which is costly.

Separation of FOG and Water • FACT: Grease won't mix with water because it is 10 to 15 percent less dense than water. • The separation of a FOG from water is inversely proportional to the density and viscosity of the water, density and diameter of the FOG, and the temperature of the water/FOG material. • The rate of ascension will be faster when the carrier fluid is less viscous, the FOG is at a higher temperature, and the FOG particles are large.

Regulating Disposal • Fat, oil, and grease (FOG) blockages are the primary cause in 4050% of all sanitary system overflows (Southerland, 2002). • 1973, the Environmental Protection Agency (EPA) established regulations to limit what commercial buildings can discharge into the sewer and by extension into the local water treatment plant. • These regulations gave the EPA the power to fine municipalities for Sanitary Sewer Overflows.

What can interceptors be used to separate?

Where are Interceptors used?

What are Interceptors made of? • Interceptors can be made of many different materials such as: • • • Concrete Steel Stainless Steel Fiberglass Plastic • Other issues to consider when deciding the best option are corrosion resistance, cost, required space to locate the grease interceptor, etc. . .

Corrosive Effects on Interceptors • A 2008 Water Environment Research Foundation (WERF) report determined that the waste water in a grease interceptor is so acidic that it meets EPA requirements for neutralization (p. H<5). • Typically, the p. H level within a gravity grease interceptor will drop below a p. H of 5 within a week of its operation. • Acidic waste with a p. H<5 is very corrosive to steel, concrete, and fiberglass interceptors alike.

Steel Interceptors • The effects of a highly acidic p. H level results in 5 years as the typical life expectancy of a steel grease interceptor. • In addition to the actual cost of a replacement grease interceptor, the owner has to contend with a disruption to their facility and the labor/cost to tear out and dispose of the rusted steel grease interceptor.

Concrete Interceptors • The Portland Cement Association has stated that fats, fatty acids, vegetable oils, salts, sugars, acids, bleach and even water will disintegrate concrete even with proper protective coatings. • Over time, concrete interceptors will crack and deteriorate, leaching contaminated waste water into the ground. • 10 years is the typical life expectancy of a concrete grease interceptor.

Fiberglass Interceptors • Fiberglass is hard and stiff, which makes it subject to cracking. • Additionally, it is known that a low p. H level (below 5) within a fiberglass grease interceptor will exacerbate its brittleness. • Fiberglass interceptors also have a negative environmental impact because they are made with VOCs – (Volatile Organic Compounds). • Countless cases of fiberglass interceptors caving in have been reported; one involved a Volkswagen Beatle collapsing the fiberglass tank after driving over it and needing to be pulled out in the aftermath. • Normally only offered with 30 year warranty.

HDPE Interceptors • HDPE = High Density Polyethylene • Will not crack, chip or bulge under extreme impact, sunlight and / or temperature changes. • HDPE has a greater resistance to a number of chemicals, and is the same material used in Acid Neutralization tanks. • HDPE interceptors are offered with a limited Lifetime Warranty which makes them by far the most economical choice from the beginning. • Rotationally molded HDPE interceptors have NO negative environmental impact.

Issues with Sizing • It is typical for a local authority to require the installation of a 1, 000 gallon liquid holding capacity grease interceptor regardless of the restaurant type and size. • The “bigger is better” thinking has led to new issues including difficulty accessing the grease interceptor for cleaning, cost of pumping out the grease interceptor, and accumulation of hydrogen sulfide (H 2 S) gases from extended pump out frequencies. • These large interceptors must be pumped out after just 25% of their volume is filled, because after that they no longer work well enough to keep fats and oils out of the sewage systems.

Safety Concerns When Sizing • An incorrectly sized Interceptor can lead to extreme grease pass through causing regular snaking of the downstream drain lines, excessive fines from the pre-treatment authority, gas build-up, and most importantly corrosion deteriorating the interceptor until failure. • Unfortunately in 2008, two people died after inhaling noxious H 2 S gases from a large grease interceptor at the Orleans Hotel & Casino in Las Vegas. • http: //articles. latimes. com/2008/jul/28/nation/na-vegas 28

How does the Grease Separate?

Stokes’ Law • Interceptors are required to receive the drainage from fixtures and equipment with FOG-laden wastes. • Retention time as a key element in the design of a basin. • The hydraulic environment and size of the FOG particles, induces the separation of FOG and the deposition of solids within the interceptor. • The separation of FOG from water by gravity differential can be expressed mathematically by Stokes’Law which governs the rise and fall rates of an oil droplet or solid particle in the fluid stream.

FOG Separation • The American Society of Plumbing Engineers (ASPE) established three inches as the minimum distance that a grease globule must rise in an interceptor to be retained. • Using the example of a 21. 33 gal capacity interceptor (22”Lx 14”Wx 20”H) with a 2” inlet/outlet at a 20 gpm flow rate, calculating a 3” rise at 68°F: • FOG droplet size and velocity determine the minimum outlet elevation needed to capture the targeted FOG globule. Affect of FOG size and specific gravity

Inlet Design • Some turbulence is unavoidable at the inlet end of the tank. This effect is greatly reduced by good inlet design (including baffling). • The designer can improve the grease interceptor by increasing the interceptor volume or reducing flow and subsequently lowering horizontal velocity and increasing retention time. • The ideal inlet reduces the inlet velocity to prevent the pronounced currents toward the outlet (flow control device), distributes the inlet water uniformly over the cross-section of the tank, and mixes the inlet water with the water already in the tank to prevent the entering water from short-circuiting toward the outlet.

Best Option for Inlet Setup WERF 2008 Study • The distributive tee is most effective at separating FOG and solids from the waste stream. • One explanation for the higher accumulation of oil and solids is the slower inlet velocity with the distributed tees. The slower inlet velocity, which is caused by an increase in the cross-sectional flow area, allows more effective separation by permitting the upward migration of the oil droplets or downward particle settling.

Where are Samples Taken From?

FOG Separation Day 12/13

Solids Separation Day 12/13

WERF 2008 Separation Results • Short circuiting of the inlet flow can occur if the inlet velocity is too high at a specific location. With the no inlet tee, the flow enters the GI at the surface at one location. The higher velocity at this entrance point reduces the time that is necessary for proper separation within the first performance compartment. Consequently, FOG accumulation and solids deposition is occurring in the second chamber. • The standard configuration clearly shows the potential for re-suspending settled solids once the solids have accumulated to a certain depth. • In the case of the distributed tee inlet configuration, the influent velocity is reduced since the flow is distributed over a greater pipe cross-sectional area. The lower influent velocity allows FOG and solids to separate more effectively in the first chamber and little carry over of FOG and solids occurs in the second chamber.

Styles of Interceptors

Styles of Interceptors • There are (2) styles of Interceptors: • Gravity Grease Interceptors (GGI) • These interceptors are often greater than 500 gallons in liquid capacity, but hold a small percentage of their liquid capacity in grease and are not certified to meet any efficiency standards. • Today’s gravity grease interceptors use the same basic operating design as the first U. S. patented interceptor in 1885. • Hydromechanical Grease Interceptors (HGI) • Engineered so they never lose efficiency, these interceptors can hold upwards of 90 percent of their volume in grease before they must be cleaned out. • Most HGI's must be certified to a standard such as: • PDI-G 101 (1949) • ASME A 112. 14. 3 (1994) • CSA B 481 (2007)

Gravity Grease Interceptors (GGI) • The separation of FOG is based on the capacity and retention time within the interceptor. • Does not require the use of a flow control fitting or internal flow control and is typically buried outside buildings eliminating possible food contamination during cleaning and preventing delays in kitchen operation. • The flow rate is calculated to determine the highest possible peak flow coming from the drainage fixtures and equipment in the food preparation area and multiplied by a retention time to achieve the liquid holding capacity (in gallons) required for the grease interceptor.

Gravity Grease Interceptors (GGI)

Sizing Gravity Grease Interceptors • The 2015 Uniform Plumbing Code establishes the volume of a GGI based on a table of drainage fixture units (DFUs). • Where DFUs are not known, the interceptor shall be sized based on the maximum DFUs allowed for the pipe size connected to the inlet of the interceptor (refer to Table 703. 2 in the 2015 UPC). • Interceptors are typically required by IAPMO to have: • • • a 30 minute retention time baffle(s) no less than two compartments a total volume greater than 300 gallons of liquid holding capacity gravity separation

Sizing Gravity Grease Interceptors • The local authority having jurisdiction has the final say in the sizing of a grease interceptor, so always contact the AHJ to determine which code or method to use before beginning the design. • The flow rate of the GGI is calculated to figure the possible highest flow produced by the drainage fixtures and equipment in the food prep area and then multiplied by retention time (usually determined by the local municipality) to produce the liquid volume (in gallons of water) needed for the grease interceptor. • The Codes provide drainage fixture-unit values based on drain outlet or trap size.

IAPMO Z 1001 DESIGN STANDARD Sizing 1. Define the fixtures feeding the interceptor. 2. Identify the fixtures DFU’s. 3. Add up all DFU’s and size accordingly.

Fixture Outlet Sizing • The majority of plumbing codes list the drainage fixture-unit values for plumbing fixtures, but not all fixtures are listed. • The Codes also provide drainage fixture-unit values based on drain outlet or trap size. Drainage fixture-unit values are converted to GPM discharge rates on the basis of one drainage fixture-unit equaling = 7. 5 GPM fixture discharge rate.

Advantages of Hydromechanical vs. Gravity • A typical 1000 gallon concrete gravity interceptor has an estimated grease design capacity of 1, 020 lbs. • A 100 GPM hydromechanical grease interceptor has a grease design capacity of 1, 150 lbs. • A GGI with a liquid holding capacity of 1, 000 gallons can only function to a point where 250 gallons (1, 000 x. 25) of its volume is occupied by solids and grease. • Assuming that 100 gallons is solid material, then only 150 gallons of grease capacity remains before cleaning is required. This equates to approximately 1, 090 lbs. of grease. • In comparison, a HGI has a significantly smaller 300 gallon liquid holding capacity but a third party laboratory tested grease separation efficiency of 90%. This translates to essentially the same grease capacity as the GGI, exceeding 1, 000 lbs. of functional grease capacity.

Hydromechanical Grease Interceptors (HGI) • Designed to use modulated flow, air entrapment, and internal features to provide an enhanced level of separation efficiency. • The ASME A 112. 14. 3 Standard Sections A and B require the use of an external vented flow control fitting; as well as PDI G-101. ASME A 112 -14. 3 Sections C and D do not require the use of an external vented flow control fitting. Section A, B, and C are directly connected. • The flow rate is calculated to determine the highest possible peak flow coming from the drainage fixtures and equipment in the food preparation area. • The sizing method for HGI is based on the flow rate expressed in GPM (Gallons Per Minute), generally available with a rated flow capacity up to 100 GPM.

Hydromechanical Grease Interceptors (HGI)

Sizing Hydromechanical Grease Interceptors • Reliable performance of any grease interceptor is dependent on being correctly sized to handle the drainage load from the fixtures it serves. • Hydromechanical Grease Interceptors can be sized using 2 methods: 1. PDI G-101 requirements 2. Grease Production sizing

Method 1: PDI G-101 Requirements 1. Calculate the volume in cubic inches of all the fixtures to be served by the Grease Interceptor. (length x width x depth). • Cubic contents of one sink compartment = 18 × 24 × 12 = 5, 184 in 3 • Cubic contents of three sink compartments = 3 × 5, 184 = 15, 552 in 3 2. Divide this number by 231 to convert the volume to US gallons. • Contents expressed in gallons = 15, 552 in 3 /231 = 67. 3 gal 3. Determine the fixture load. A sink seldom is filled to the brim, and dishes, pots, or pans displace approximately 25 percent of the water. Therefore, 75 percent of the actual fixture capacity should be used to establish the drainage load. • 0. 75 × 67. 3 gal = 50. 8 gal 4. These calculations are based on a one minute drain down time (gallons per minute). If a two minute drain down time is applied, then divide the GPM by two. • Result: Hydromechanical Interceptor sized for 50 gpm

Alternative: Sizing by Grease Production • Some industry people believe that sizing grease interceptors based on the amount of grease that is produced in a restaurant or kitchen makes a lot more sense than sizing based on flow rate of water and / or drainage fixture units going into the grease interceptor. • Selecting an HGI that can only store the minimum required amount of FOG may be problematic in that the food service establishment could be required to conduct maintenance on a biweekly, or even daily basis.

Method 2: Grease Production Sizing • The following optional selection method for HGIs allows an engineer to calculate the potential daily grease load that may be anticipated from a given food service establishment to select an interceptor that meets the minimum required flow rate previously established with a larger grease storage capacity. • This can be done first by flow rate and then by grease capacity for pump-out cycle.

Method 2: Grease Production Sizing • The following information and sizing charts can be used to size grease interceptors based on the grease produced in a variety of different restaurants.

Method 2: Grease Production Sizing Refer back to Step 1 for the min required flow rate.

Installation Recommendations • It is recommended to locate the interceptor as close to the greaseproducing fixtures as possible. • Flow controls are best located immediately downstream of the last drain of the fixtures served prior to the interceptor. • Venting is required on the downstream drain line – the same as most other plumbing appliances and fixtures to allow efficient and unrestricted discharge of the waste water. • (GGI) are required to be directly vented. • (HGI) are not required to be directly vented unless specifically mandated by local code or by law.

Uniform Plumbing Code for Interceptors (UPC) • Water closets, urinals, and other plumbing fixtures containing human waste shall not drain into any interceptor. • No food disposal or dishwasher unit shall be permitted to discharge into any grease interceptor. • Each fixture discharging into an interceptor shall be individually trapped and vented in an approved manner. • Each business establishment for which a gravity grease interceptor is required shall have an interceptor that shall serve only that establishment.

International Plumbing Code for Interceptors (IPC) • Hydromechanical grease interceptors shall meet the minimum grease retention capacity for the flowthrough rates indicated in Table 8 -3. • Where food waste disposal units are connected to grease interceptors, a solids interceptor shall separate the discharge before connecting to the interceptor. • The flow control device shall be vented and terminate not less than 6” above the flood rim level.

Heat Tracing • Grease interceptors are increasingly installed further away from the kitchen – often outside of the building. Pipe insulation alone is not enough to keep grease waste flowing. • Some ordinances do not allow the installation of interceptors where the surrounding temperatures under normal operating conditions are less than 40°F. • If this cannot be achieved due to field conditions or other site constraints, a heat trace system can be installed along the grease waste piping to the inlet side of the GGI to help prevent FOG from solidifying before it enters the interceptor. • FOG separates best when the waste water is hot – typically between 109. 4°F – 120. 2°F.

The Need for Maintenance • Efficient grease interceptor function is directly related to properation and maintenance. • Accumulations greater than the intended storage capacity affect flow characteristics and diminish separation and retention efficiency. • FOG is not a stable compound in an aqueous environment. • Cleaning products and bacteria in a grease interceptor accelerate decomposition, which results in acidic p. H levels, oxygen depletion, and the alteration of specific gravity. • A lack of regular service can result in the release of system-damaging compounds, noxious odors, and excessive interceptor corrosion.

CEU Quiz ASPE Members please login to ASPE website and use the link below https: //aspe. org/Education. Registration? Item. Number=318

Tables need for Questions

Questions 1 -6

Questions 7 -12

For 0. 1 CEU Credit ASPE Members please login to ASPE website and use the link below https: //aspe. org/Education. Registration? Item. Number=318 1. D 2. B 3. D ANSWER KEY 4. A 7. D 5. A 8. B 6. B 9. D 10. B 11. C 12. C