PREVENTING SEWAGE OVERFLOWS AND SPILLS - Page 2
What is the difference between "sanitary sewers" and "storm drains"?
"Sanitary sewers" collect and convey sewage to a treatment plant where the sewage can be treated. It is important to understand that sanitary sewers are a completely different set of pipes from "storm drains."
In Hawaii and most other areas, an independent system of pipes called "storm drains" is used to only transport storm water (i.e., rainwater) to streams, bays and the ocean with little or no treatment. The separate "sanitary sewer system" (see definition above) is "sanitary" because it keeps sewage out of the storm drains and sends the sewage to a treatment plant before it is released into the environment.
Some key points to remember are:
- Sanitary sewers have limited capacities and are not designed to dispose of storm water (i.e., rainwater) from your property.
- Storm drainage flows are generally not treated and therefore should not contain any pollutants that could affect our streams and ocean.
- Rubbish should not be thrown down sewers or storm drains. Because sewage is treated, sewers can handle sewage as well as certain types and limited amounts of "toxic" materials such as household cleaners.
Sewage spills are simply an overflow of untreated or partially-treated sewage from the sewer system (i.e., the raw sewage overflows from a sewer line before it reaches the wastewater treatment plant). The sewage can overflow from the manholes in the streets, from open cleanout lines, or from toilets and drains in your home.
In really bad situations, someone else's sewage could spill out of your toilet or shower and flood your home! Yuck!! This may not happen to you but what you do in your home could cause it to happen to someone else living farther down the sewer line!Sewage spills are a big problem because:
- Sewage spills cause public health problems. Spills can expose people to disease-causing germs (pathogens) such as E. coli and Cryptosporidium that are present in sewage.
- Sewage spills can pollute our streams, the ocean and other bodies of water. In addition to being a public health problem, sewage can add unwanted nutrients to our water environment and cause excessive growth of algae that disrupts the ecosystem.
- Sewage spills can pollute the groundwater, which in many inland areas, is our source of drinking water.
- Sewage spills hurt our economy. Sewage spills are costly to clean up and this affects our sewer bills (which almost everyone feels are already too high!). More importantly, sewage spills can cause beach closures that can have a big impact on Hawaii's tourism-based economy.
Sewage spills are caused by the clogging of pipes and/or too much flow. Clogging is caused by blockages from fats, oils and grease as well as rubbish, roots and other foreign or unwanted objects in the sewer system. Too much flow is caused by infiltration and inflow (i.e., groundwater and rainwater getting into the sewer system). The following sections discuss each cause in detail.
Keeping fats, oils and grease out of the sewer system
Fats, oils, and grease, and other byproducts of cooking come from meat, lard, shortening, butter, margarine, food scraps, sauces, and dairy products. They present a significant clogging problem for sewer systems. Fats, oils and grease stick to the inner walls of sewer pipes and reduce the diameter of the pipes over time. This eventually causes clogged sewer pipes and sewage spills. 
Clogging is further caused by chunks of grease breaking away from the pipe walls and becoming stuck further down the line. Grease balls that form when grease combines with sand, grit, and other sewage debris can even become large and hard enough to clog sewage pumps! Fats, oils and grease also flow down to the wastewater treatment plants where it disrupts operations and increases maintenance costs.
Regulations require restaurants and other commercial food handling facilities to install large grease separation devices to protect sewers from grease problems. Folks at home need to do their part!
How should we properly dispose of grease and oils?
Everyone can do their share to prevent clogged sewers by following these simple Do's and Don'ts:
DO's:
Collect oil and grease in a container filled with absorbent material (shredded newspaper, napkins, paper towels, rags, etc.) and properly dispose of it in the garbage.
- Scrape grease and food scraps off cooking/serving utensils and plates for proper disposal. Better yet, wipe them with used napkins and paper towels before washing.
- Encourage friends and neighbors to practice similar habits of proper oil and grease disposal. Parents, set a good example for your kids! Kids, educate your parents!
- Do not pour grease or oil down the drain or toilet.
- Do not dump greasy or oily food waste into the drain. (Minimize the use of your garbage disposal and better yet, compost your vegetable scraps!)
- Be sure to put your oil and grease in a suitable container or bag with absorbent material. The reason for using the absorbent material is so that your grease and oils do not leak out of garbage trucks and cause a big mess. Also, remember that solid grease can turn to liquid in our hot climate so use absorbent material for solid or semi-solid fats too!
- If you have a large amount of cooking oil, consider using a disposable automotive oil change box filled with absorbent material. For even larger quantities (several gallons or more), take your used cooking oil to a recycler (check your yellow pages).
- On Oahu, your trash is sent to HPOWER and therefore, instead of causing a costly sewer and environmental problem, throwing your fats, oils and grease in the trash is now helping to generate power and save everyone money!
Your toilet and sewer system are only designed to dispose of human wastes and toilet paper (which quickly breaks down). Unfortunately, people use the toilet as a wastebasket out of convenience. It is a huge "out of sight, out of mind" problem because people often don't see the mess sewer overflows cause and the problems that sewer workers need to deal with!
Almost any type of rubbish may restrict sewage flow, clog sewers, and cause sewage overflows. Keep the following from going down your toilet and sinks:
- Paper (paper towels, facial tissue (Kleenex), paper napkins, wrappers, etc.). Only toilet tissue is okay!
- Plastics (bags, wrappers, bottles, cotton-tip shafts),
- Rubber (gloves, condoms, underclothes elastic, etc.),
- Cloth and fibers (cotton balls, tampons, cigarette filters, stockings, rags, etc.).
- Food scraps (greasy items are the worst but minimize throwing down non-greasy items too. Try to even keep out smaller food items such as tea-leaves, coffee grounds or eggshells. Garbage grinders help but its even better not to use it where possible -- compost what you can and throw the rest in the trash. Place food scraps in tightly sealed bags or other containers so it does not become an odor or rodent problem.)
- Toys, cans, sticks, pebbles and sand, and pretty much all other solids except for human wastes and toilet tissue.
Do your share to keep rubbish from clogging our sewers by following these simple Do's and Don'ts:
DO's:
- Place and use a wastebasket in the bathroom to dispose of rubbish (including disposable diapers and personal hygiene products).
- Use sink and shower drain strainers.
- Scrape food scraps into sealed containers or bags and throw them out in the garbage.
- Educate each other on minimizing disposal of rubbish to our sewers.
- Don't use the sewer as a convenient means to dispose of food scraps.
- Don't use the toilet as a wastebasket!!
Last Updated: December 13, 2007