Wastewater - Glossary of Terms -


Lift Station : A point in the sewer system where the wastewater needs to be pumped (lifted) to a higher elevation so that gravity can be used to bring the wastewater to the treatment plant. In Hailey there are 2 lift stations:
1) located at the old Riverside plant that collects most of Hailey except Woodside and parts of Deerfield.
2) located at the new plant and collects Woodside, parts of Deerfield and the Woodside Industrial area. Most of lift station 1 can be diverted here in case of emergency.

Fine Screen : A machine placed in the wastestream that collects large pieces of material that may cause damage or blockages downstream such as rocks, rope, etc. Other material (like paper towels) is shredded and allowed to continue on to further treatment. This is the first piece of equipment in the treatment process at the Woodside Treatment Plant.

Grit Separator : The next device in the wastestream. As the wastewater goes around, it slows down and the heavier sand and grit settle in the bottom. Every hour or so, the settled grit is forced by air into a grit classifier. Here the grit is separated from the water and, by use of a screw drive, is discharged into a dumpster that is emptied every 3 days.

Preliminary Treatment : The above 2 devices are considered preliminary treatment. The point of preliminary treatment is to protect the pumps and other equipment in the plant and to reduce down time due to blockages and damage.

Primary Treatment : A step in the treatment process where solids are removed through settling or floating. The floating solids (scum) is then taken to a land fill or burned. It increases the efficiency of plants where the wastewater has only limited contact with the bacteria. Since this plant has long contact periods, this step is skipped.

Secondary Treatment : Usually a biological process where bacteria oxidize or breakdown organic matter that is missed by primary treatment. At Woodside, the bacteria take care of all the organic material (no primary). Also during this time nutrients are removed by either being taken up by the bacteria or converted into other substances (e.g. ammonia nitrogen converted into nitrogen gas). In an SBR plant, secondary treatment is accomplished in several fixed steps:

1) mixed fill - new wastewater is mixed with old without oxygen
2) aerated fill - mixing with forced air (aeration)
3) react - mixing while switching between air and no air
4) settle - no mixing, no air
5) decant - removing 'clean' water from basin
6) waste - bacteria are taken out of the basin (idle if wasting is not needed).

Reactor Basin : Large (81'x 81'x 21') concrete tank where various steps of secondary treatment occur.

Aerobic Bacteria : These bacteria require molecular oxygen in order to consume food (organic material and nutrients). If not enough oxygen is present, the treatment process will suffer because the bacteria cannot do the required steps. When these bacteria are predominate, there should be no foul odor just a musty or earthy smell.

Anaerobic Bacteria : These bacteria become inactive in the presence of molecular oxygen. They oxidize food by stripping oxygen from other sources such as sulfate and sulfite. If wastewater is without oxygen for long periods of time, the odors will be unpleasant (e.g. rotten egg smell), the water will be septic, and damage to concrete and metal can occur because of the formation of sulfuric acid.

Sludge : The solids in the basin which settle. It is composed of mostly bacteria and unconsumed organic matter.

Settle : The point in the process where the sludge is allowed to drift to the bottom of the basin and separate from the liquid. There is no mixing or aeration during settle.

Supernatant : The liquid layer that is drawn off the top of the basin after settling. It should be relatively clear and free of solids. AKA decant.

Tertiary Treatment : Any process that upgrades effluent quality to meet specific reuse requirements such as fishing, boating, and swimming. Removes specific contaminants that conventional treatment cannot. At this plant it consists of a final 20 Ám filter to remove fine non-settleable solids. AKA Advanced treatment.

Disinfection : The inactivation or killing of pathogens. This plant uses UV lamps to disrupt the DNA of pathogens which makes them unable to reproduce. Most plants use chlorine but it's dangerous to handle and may create unhealthful by-products. Disinfection is not the same as sterilization which is killing all organisms and not just the ones that cause disease.

Pathogens : Organisms that can cause disease. Many of the pathogens in wastewater are killed during the treatment process before disinfection because the environment is not right for them. Other pathogens (e.g. E. coli) that can survive in many different environments need to be removed by disinfection.

Wasting : Removal of excess bacteria that would cause settling problems. If the bacteria produced throughout the day were not removed, they would build up to a point that the sludge could not settle and the effluent quality would be poor.

Effluent : Any discharge coming OUT of a basin or tank. Most commonly refers to the final product of a treatment plant. Influent is flow INTO a basin or tank.

TSS (Total Suspended Solids) : A required test where a sample of known volume is passed through a filter and the solids remaining on the filter are weighed. Reported as mg/L (milligrams per liter). Too much TSS in the effluent would be seen as cloudiness and also as an indication that there is a problem with the process.

BOD (Biochemical Oxygen Demand) : By measuring the amount of oxygen bacteria use over a period of time, the amount of organic matter in that sample can be determined. This test is required to be done weekly and is also reported in mg/L. A high BOD in the effluent is undesirable because it would deplete oxygen needed by fish in the river.
   
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