Without any filtering or cleansing, water on the ground flows down storm drains and into rivers, streams, and the bay. Water that drains from your sinks, toilets, and inside drains is routed via the sanitary sewer system and treated to eliminate the majority of contaminants before being dumped into the bay. The rest of the trash and garbage in our streets goes into dumpsters or recycling bins.
Some cities have programs to clean out their streets and sidewalks of snow and other debris prior to the arrival of spring. This helps make walking and biking safer for everyone who uses the streets.
Debris such as glass, plastic, paper, and metal can enter our waterways through normal wear-and-tear during heavy rainstorms or when it snows. Some items may be swept away by floodwaters or blown into bodies of water as large particles. Other items may be ingested by animals which then pass them along to humans through their feces. Finally, some items may be thrown into our streets during wind or earthquake storms. All of this material should not be present in our storm drains because it will clog them up and prevent any water from flowing.
For most streets, the default route for water runoff is through the city's storm drain system. Some streets, however, have surface drains that carry water directly from the street to a sewer line or other type of treatment facility.
Aid in the Prevention of Sewage Spills into the Bay
Your water drains into a septic tank if you are not linked to a sewage system. The majority of the sediments settle out in the tank, while the liquid water flows via subterranean pipes with holes punched into them, allowing the water to seep out and into the earth. The pipe is called the drainpipe.
The size of your tank depends on how much water you use each day. Your septic tank must be large enough to hold all the water that drains from your house during an average storm event. Most tanks are about 30-40 gallons, but sizes up to 200 gallons are available. A larger tank will store more water and be less likely to overflow during a heavy rainstorm.
Overflow pipes connected to the tank allow any extra water to escape if the tank becomes full. These pipes should be installed so that they do not connect to the household plumbing - otherwise, you might end up with a bucket load of dirty water when there's a blockage somewhere in the sewer line! If the overflow pipe does connect to the household plumbing, then make sure that it has a 3/4" diameter hole at the connection point to allow for some water to escape.
Your local building department can tell you the maximum allowable volume of a septic tank. This is usually shown on your property survey.
Stormwater is carried via paved roadways with curb and gutter and into the storm sewer system through inlets or catch basins in residential neighborhoods with urban streets. A catch basin collects water from the roadway and directs it to the storm sewer pipe beneath the street, which finally leads to the storm sewer system outlet. The water flows through these pipes quickly due to their depth (about 24 inches) and diameter (about 3/4 inch).
The City's municipal water supply system is separate from the storm water system. Water from the municipal source is filtered through deep wells before being delivered to customers. Some of this filtrated water is returned to the surface through canals and other areas not requiring intense pressure. This "return flow" is either directed into adjacent land or back down into deeper parts of the well for additional filtering.
The remaining filtrate enters the storm sewer system through manholes located along streets across the city. As rainwater flows over these manholes, it seeps into small openings within the metal ring that surrounds them. This water then flows into underground pipes where it is transported by gravity to local treatment plants for further processing before being released into local waterways or back into the municipal water supply system.
These same manholes also provide a way for residents to access and maintain their own plumbing systems.
Water that leaves our homes either goes into a septic tank in the back yard and seeps back into the earth, or it is routed through a sewer system to a wastewater-treatment facility. Primary treatment is transferring water into big tanks and allowing solid matter to settle to the surface. The remaining liquid is called secondary treated waste water. It can be sent to a landfill or recycled.
The primary method of treating sewage before it is discharged into local waterways is known as biological treatment. This process requires oxygen in sufficient concentrations to support all the microorganisms needed for treatment. Organic material in the sewage provides nutrients for bacteria to break down other substances. The by-products of this breakdown include carbon dioxide, hydrogen sulfide, and nitrogen compounds.
Physical treatment methods such as filtration remove larger solids from the sewage stream before it enters a treatment plant. Chemical treatment uses additives to dissolve or precipitate materials out of the sewage stream. These additives can be natural or manufactured products found in household cleaners or pesticides.
Wastewater contains chemicals from medications taken by humans and their animals, as well as pollutants from industries. If not treated properly, these substances enter our lakes and oceans, causing health problems for fish and other organisms that depend on them for survival.
Treatment facilities use special processes to reduce the amount of harmful chemicals in wastewater before it is released into local streams and rivers.