Filtration by Severn Trent
Tertiary & Wastewater Treatment System
The key to the success of any wastewater program is to employ technology capable of producing advanced wastewater treatment plant effluent that is safe and cost effective.
Tertiary filtration and disinfection of secondary effluents are the acceptable and prevailing technologies for meeting this challenge.
The need for water resource management program coupled with the occurrence of more stringent water quality standards governing treated wastewater either for disposal/discharge, reuse or reclamation places significant importance on the use of Severn Trent Services TETRA® DeepBed™ filters to successfully produce quality advanced wastewater treatment plant effluents.
Severn Trent Services’ complete product line includes application-specific engineered gravity, pressure and modular filters and pre-assembled gravity deep bed filters.
Severn Trent Services offers the TETRA® T Block™ and TETRA® SNAP T™ underdrain filters for wastewater applications. Their proven designs provide superior distribution for both water and air, separately or concurrently.
Denite is a fixed-film biological denitrification process that also serves as a deep bed filtration system capable of removing suspended solids to virtually any final effluent requirement.
The system integrates well with other plant treatment processes to provide superior total nitrogen (TN) and phosphorous removal. Denite is used as the final treatment step in the total nitrogen removal process to help each facility meet stringent TN discharge limits of 3 mg/l.
Effective removal of nitrate-nitrogen is undertaken by introducing a carbon source, such as methanol, using the proprietary TETRAPace® automatic dosing control for savings of up to 30% in carbon consumption.
The Denite system employs a patented SpeedBump® operation to remove or purge accumulated gas – nitrogen or CO2 – that can build up in the filter media that can be accomplished without removing the reactor from service.
TETRA Denite offers consistent and proven performance – even with low water temperatures – all in a footprint one tenth of the size of a conventional suspended growth system. Percent of return of wastewater is less than 4% (<2% typical) of the plant’s forward flow.
Deep Bed Treatment
A DeepBed filter may be defined as a granular filter for removal of TSS from secondary treatment effluent using a media depth of at least four feet or 1.2 metres. Coarse media is normally used to encourage deep penetration of solids into the media bed.
This allows for longer filtration runtimes. Simultaneous air and water backwashes are used to ensure cleaning of the filters as required. Severn Trent Services has successfully provided gravity, pressure and modular filters and pre-assembled modular gravity deep bed filters to more than 300 installations worldwide.
In addition to TSS removal, TETRA® DeepBed™ and Pressure Filters are frequently specified to reduce BOD levels; achieve metal consents associated with chemical dosing for phosphate removal; improve effluent clarity for UV disinfection; and offer additional protection for works at risk of consent failure.
DeepBed Gravity Filters
The TETRA Deep Bed Filter technology is built on the TETRA T Block and SNAP T Block. As well as offering excellent distribution of backwash air and water, TETRA DeepBed filters deliver high loading capacity and superior capability at handling peak loads.
With no nozzles, screens or moving parts, TETRA DeepBed Filters do not clog or wear. The percent of dirty backwash water return is less than 4% (<2% typical) of the plant’s forward flow and the system can be readily expanded into denitrification mode.
DeepBed Pressure Filters
Modular DeepBed Filters