Texas Basic Waste Water Operations Ch#09 Fixed-Film Treatment

The fixed-film biological processes include the trickling filter and Rotating Biological Contactor (RBC). The microorganisms in fixed-film processes are usually attached to rock or plastic media.

The four basic parts of a trickling filter are as follows: • Media • Underdrains • Tank (walls/floor) • Distributor

The media provides a surface on which microorganisms grow. The biological growth is called zoogleal mass. The zoogleal mass breaks down organic material in the wastewater. Zoogleal mass consists of aerobic, anaerobic, and facultative organisms, including bacteria, protozoa, and fungi. The media is usually rock or molded plastic.

The media provides a surface on which microorganisms grow. The biological growth is called zoogleal mass. The zoogleal mass breaks down organic material in the wastewater. Zoogleal mass consists of aerobic, anaerobic, and facultative organisms, including bacteria, protozoa, and fungi. The media is usually rock or molded plastic.

The media provides a surface on which microorganisms grow. The biological growth is called zoogleal mass. The zoogleal mass breaks down organic material in the wastewater. Zoogleal mass consists of aerobic, anaerobic, and facultative organisms, including bacteria, protozoa, and fungi. The media is usually rock or molded plastic. NOTE: the same paragraph referenced three times in a row..... could be important..........

The underdrain, >located under the media<, collects filter effluent, supports the media, and transmits air to the media. The underdrain must run no more than half full to allow air circulation throughout the media.

The distributor is rotary (most common) with fixed nozzles. The rotary distributor consists of two or more horizontal pipes supported a few inches above the media by a central column. Wastewater flows from the column, through the pipes, and is distributed over the media through orifices along one side of each pipe. The jet action of the outflowing wastewater rotates the distributor. The zoogleal mass must stay wet or it will die. During low flow, clarifier effluent is recirculated, usually using centrifugal pumps, through the distributor to keep it moving and to keep the media wet.

The distributor is rotary (most common) with fixed nozzles. The rotary distributor consists of two or more horizontal pipes supported a few inches above the media by a central column. Wastewater flows from the column, through the pipes, and is distributed over the media through orifices along one side of each pipe. The jet action of the outflowing wastewater rotates the distributor. The zoogleal mass must stay wet or it will die. During low flow, clarifier effluent is recirculated, usually using centrifugal pumps, through the distributor to keep it moving and to keep the media wet. NOTE: yes, i was lazy.....

Wastewater distributed on the media must first pass through a primary clarifier or fine screen to remove heavy solids that would clog the distributor nozzles; however, the wastewater still contains about 65% of the organic matter. The organic matter feeds the organisms growing on the media.

When the zoogleal mass grows thick, some of it sloughs off or breaks off. The sloughed material is called sloughings. The sloughings wash into the underdrain, then settle in a secondary clarifier.

Sloughed material settled in the final clarifier is called >humus< sludge. Humus sludge is usually pumped to the digester or to the primary clarifier to resettle, and then pumped to the digester with the raw sludge.

The fixed-film biological processes include the trickling filter and Rotating Biological Contactor (RBC).

Filters are classified by hydraulic and organic loading. Hydraulic loading is the volume of water, including recirculation, applied to the filter in gallons per day/square foot (GPD/square foot) of media or million gallons per day per acre (MGD/acre) of media. Organic loading is in pounds of BOD per day per acre-foot or 1,000 cubic feet of media. An acre-foot is 1 surface acre (43,560 ft2 ) that is 1 foot deep.

Filters are classified by hydraulic and organic loading. Hydraulic loading is the volume of water, including recirculation, applied to the filter in gallons per day/square foot (GPD/square foot) of media or million gallons per day per acre (MGD/acre) of media. Organic loading is in pounds of BOD per day per acre-foot or 1,000 cubic feet of media. An acre-foot is 1 surface acre (43,560 ft2 ) that is 1 foot deep.

Filters are classified by hydraulic and organic loading. Hydraulic loading is the volume of water, including recirculation, applied to the filter in gallons per day/square foot (GPD/square foot) of media or million gallons per day per acre (MGD/acre) of media. Organic loading is in pounds of BOD per day per acre-foot or 1,000 cubic feet of media. An acre-foot is 1 surface acre (43,560 ft2 ) that is 1 foot deep. NOTE: same paragraph referenced 3 times..... might be worth paying attention to....

The BOD test measures wastewater strength, filter efficiency, and effluent quality. Standard rate filters remove 80–85% of the BOD. NOTE: TSS = Total Suspended Solids, DO = Dissolved Oxygen, SV30 = 30 minute settling test, BOD = Biochemical Oxygen Demand (Biochemical oxygen demand is an analytical parameter representing the amount of dissolved oxygen consumed by aerobic bacteria growing on the organic material present in a water sample at a specific temperature over a specific time period. The values you will see and use in calculations are BOD which specifically are results of the BOD5 test so named because it takes 5 days to complete. i dont approve of the way TEEX uses the two terms interchangeably when they refer to separate items so i want to be very clear that when you see "BOD5" it refers specifically to the 5 day test itself and when you see "BOD" it should refer specifically to the value/results the test yields. given that the answer should read BOD5 not BOD but this is how TEEX wrote the answer key and its likely how you will see it in a graded evaluation.

Problems associated with trickling filters are listed as follows: • Filter flies • Odor • Ponding • Clogged nozzles • Clogged underdrains • Snails • Excessive sloughings • Mechanical problems

Filter flies (Psychoda) are tiny dark-colored moths that are not a health threat, but are a nuisance to operators and neighborhoods. The larvae live in the slime of the filter and are most common in standard rate filters. Filter flies live in an environment that alternates between wet and dry.

Odor results when treatment becomes anaerobic. Take action if high organic loading or hydrogen sulfide is present. Increase recirculation, pre-chlorinate, or add forced ventilation. Additionally, check vent pipes and underdrain for an obstruction. If underdrains are more than half full, reduce hydraulic loading. Finally, check for excessive zoogleal growth. If necessary, increase recirculation, which will increase the sloughing process. NOTE: While some odor is produced from the processes listed as answers it is specifically referring to the malodor caused by the byproducts produced by anaerobic processes (hydrogen sulfide H2S).

Ponding results from clogged filters caused by excessive zoogleal growth, debris, insects, snails, improper media, or poor primary treatment.

Rotating biological contactors (RBC) have a motor-rotated or air-rotated shaft surrounded by plastic media. The shaft and media are called the drum. Each drum is about 12 feet in diameter and up to 25 feet long. About 40% of the media is immersed in the wastewater.

Biological slime (microorganisms) grow on the media. As the drum rotates, wastewater flows over the microorganisms, which consume BOD using oxygen absorbed by the water from the atmosphere. In time, some media growth sloughs off and is carried by the effluent to the secondary clarifier where the sloughings settle.

Biological slime (microorganisms) grow on the media. As the drum rotates, wastewater flows over the microorganisms, which consume BOD using oxygen absorbed by the water from the atmosphere. In time, some media growth sloughs off and is carried by the effluent to the secondary clarifier where the sloughings settle.