All About Sewer Cleaning
By Joan Whetzel
Most US cities have 2 separate sewers - one for raw sewage and the other for rainwater. However, about 800 cities, including New York City, have a combined sewer system that merges storm drainage with wastewater which all gents sent through the cities' water treatment plants. It works pretty well, as long as it doesn't rain. But heavy rains and/or lines clogged with sewage tends to create nightmares. Any time wastewater or storm drainage sewer lines are clogged means a good sewer cleaning is in order.
Signs of Sewer System Problems
In a majority of US cities the sanitary sewer lines carries residential and business wastewater to the sewage treatment plants, while in a few cities the lines carry the combined wastewater and rainwater to the treatment plants. The combined systems tend to overwhelm the water treatment plants. Once the plants get behind, the water back up the lines mix with the storm runoff, causing a health hazard with rain water mixed with raw sewage in the streets, or worse, the sewage backs into homes and business. Raw sewage can also back up into homes and businesses when wastewater sewage lines become clogged and no longer drain to the treatment plants properly.
How Sewers Are Supposed to Work
Toilets, showers, and sinks in residential and business districts are connected to a city's sanitary sewer system, about 10 feet underground, much lower than storm sewers. The reason they buried lower than the storm sewers is to prevent cross-contamination in the case of pipe breakage or leaks. Routine maintenance to wastewater and storm sewers helps keep them clear of debris with restricts the flow of water or cuts it off completely, and provides an early visual warning of any problems with breaks or leaks that need fixing.
Sewer Cleaning Techniques
It's to a cities advantage to fix sewer problems early, before they become a major problem, which costs lots of taxpayers' money. The sewer cleaning techniques include:
1. High Pressure Flushing which pushes the clog out of the way, much the same as a plunger unclogs a sink or toilet line.
2. Sewer Jet Trucks are able to cut the tree roots that have grown into pipes by means of high-powered hydraulic motor which shoots water into the system and is tied to a cutting blade geared toward tree cutting.
3. Bucket Machines, mounted on trailers, clear the lines by situating two trucks over two sequential manholes. A bucket gets dragged through the sewer line, from one manhole to the next one, hopefully catching and clearing the clogs. The trucks move up alternating manholes, running the bucket up to the next manhole, until the bucket has cleared the line.
4. Vacuum Trucks work something like a huge, super-powered vacuum cleaner. A large diameter hose, attached to the vacuum truck at one end, is placed into the sewer line. Once the vacuum suction is turned on, the clog is removed from the sewer line with suction and deposited in a large tank on the truck.
Effects of Sewer Cleaning
Sewer cleaning reduces over flows due to clogs, which is especially likely in combined sewer systems, by reducing the amount of water in the sewer pipes at any one time. Removing rocks, tree roots, and debris also improves the water quality by removing the dirt, pollutants, and raw sewage clogs that make the water dirty and contaminated with bacteria, before it gets to the water treatment plant. Having it removed from the sewer pipes before the next big rain storm also ensures that these combined sewers won't back up into the city's streets or into homes and businesses, where raw sewage can make people sick.
Tipsfor Homeowners and Businesses
To help keep the sewer lines clear, homeowners and businesses can make sure that certain objects - like disposable diapers, feminine products, and rags - aren't flushed down the toilets or large amounts of food down the kitchen sink, even if the garbage disposal is being used. For storm sewers, make sure that harder objects like bottles and cups as well as large amounts of grass clippings are not swept down into the sewers.
Reference
Sanitary Sewer Cleaning. "Amherst, New York Engineering Department." http://www.amherst.ny.us/govt/govt_dept.asp?dept_id=dept_10&div_id=div_14&menu_id=menu_64
The Works: Anatomy of a City. Kate Ascher. 2005. pp 174, 182,
Sewer Cleaning and Inspection Program. "City of Winnipeg." http://winnipeg.ca/waterandwaste/sewage/mainCleaning.stm
Non-Conforming Sewer Program. "Portland Bureau of Environmental Services." 2010. http://www.portlandonline.com/bes/index.cfm?c=49974&a=204272
Pioneers in Water Treatment Solutions. "Brazos River Authority." http://www.brazos.org/waterTreatment.asp
The Texas Clean River Program. "Brazos River Authority."
http://www.brazos.org/crpHome.asp
Environmental Protection Made Clear. "Wastewater Treatment Made Clear." 2008-2010. http://www.wastewatermadeclear.ca/environment/
