Wastewater treatment tanks, equipment and residues
Wastewater tanks and residues library
Technical guidance on wastewater tanks, accumulated solids and installed equipment, with the operating limits that matter during cleaning and maintenance.
Wet wells, aeration tanks and sludge stores do different jobs within a treatment system. Their contents and equipment, together with inflow and shutdown limits, affect how cleaning is planned and what has to stay in service.
Process role: what the tank does and which treatment stages sit before and after it.
Contents: the wastewater present, retained solids and any known industrial input.
Equipment: pumps, mixers, screens and other components affected by cleaning.
Operations: normal inflow, permitted shutdown and the conditions for return to service.
Reference sources for this library
The sources below cover sewage treatment processes, wet-well solids management, work equipment maintenance, confined spaces and pollution prevention. Manufacturer material applies only to the equipment or process it describes. Site conditions and operating controls must still be assessed for the installation in question.
Balance and equalisation tanks smooth changes in wastewater flow or load. Deposits, mixing equipment and treatment continuity all affect how they can be cleaned.
Read the guide Reference notes, checklist and technical facts
Function
Buffer changes in wastewater flow or load
Possible contents
Mixed wastewater and accumulated solids
Check equipment
Mixers, pumps, level devices and connections
Critical information
Process role and permitted interruption
Process flow and the tank’s balancing role
Wastewater source and known industrial inputs
Mixer, pump and level-device arrangement
Isolation, inflow and downstream continuity constraints
Sludge holding tanks store material from treatment processes before transfer or further treatment. Sludge source, consistency and installed equipment all affect removal and cleaning.
Read the guide Reference notes, checklist and technical facts
Function
Hold sludge before transfer or treatment
Key property
Actual solids content and consistency
Equipment to identify
Mixers, transfer pumps and pipework
Waste route
Depends on sludge source and composition
Source and treatment stage of the sludge
Solids, consistency or analytical information
Mixer, transfer-pump and pipework arrangement
Sludge production, storage and transfer constraints
Storm storage tanks provide temporary capacity in wastewater systems. Sediment can remain after filling, and changing weather or inflow can affect both cleaning and return to service.
Read the guide Reference notes, checklist and technical facts
Function
Provide temporary storage within a wastewater system
Possible deposits
Settled solids and retained debris
Operating constraint
Changing inflow and weather
Separate asset
Not the same as a clean surface-water attenuation tank
Aeration tanks form part of biological treatment by introducing air into the wastewater. Cleaning must take account of the process state and the aeration equipment installed in the tank.
Equalisation mixers operate in basins used to smooth wastewater flow or loading. The tank’s operating state and mixer arrangement affect access and maintenance.
Final settlement tanks separate solids after biological treatment. Sludge collection, scraper arrangements and flow through the tank affect cleaning and maintenance.
Grit chambers remove dense material during preliminary treatment. Maintenance depends on where grit has accumulated and the equipment used to collect or remove it.
Humus tanks remove solids carried from percolating filter beds. Their position after biological filtration and the sludge-removal arrangement are the main maintenance considerations.
Inlet screens retain larger solids before wastewater passes into later treatment. Chamber layout, retained screenings and the flow path affect cleaning and access.
Percolating filter beds use process media to support biological treatment. Maintenance must distinguish material that should be removed from media and equipment that form part of the treatment process.
Solids and grease can collect in lift-station wet wells, particularly where pumping and mixing conditions allow material to settle or form a surface cap. Their location and the station layout affect maintenance.
Reed beds use a planted treatment bed as part of wastewater treatment. Maintenance depends on the designed flow path, the condition of the bed and the part of the system affected.
Sewage screenings are the larger debris retained at the inlet screening stage. Removing retained screenings is different from repairing or maintaining the screen itself.
Sludge digesters treat sludge anaerobically and produce biogas. Their contents, operating state and gas-producing process make them different from ordinary sludge storage tanks.
Sludge drying beds hold sludge during drying as part of sludge treatment. The feed material, retained solids and condition of the bed affect maintenance.
Sludge thickening reduces water content before later sludge treatment. Cleaning depends on the thickening method, the equipment involved and what sludge handling must continue while it is unavailable.
Sludge transfer pumps move sludge between storage or treatment stages. The source and destination, pump layout and deposits around the maintenance area all matter.
Wastewater grit is dense material such as sand or gravel removed during preliminary treatment. Deposits can remain in the chamber or around grit-removal equipment.
