Product category:
Waste-water handling, monitors + treatment
News Release from: Brightwater Engineering | Subject: Brightwater HSAF
Edited by the Processingtalk Editorial
Team on 23 May 2008
Wastewater treatment and its Carbon
footprint
The Brightwater HSAF process is designed to enable BOD and/or ammonia reduction, depending on its configuration, and offers a low energy technology approach to water treatment
The recently-issued 'Future Water' document, a DEFRA publication that maps the water management strategy for England to the year 2030, has as one of its core goals cutting greenhouse gas emissions from the water sector Add to this a growing concern over the escalating costs of electricity and the focus puts low-energy wastewater technologies such as the Brightwater FLI HSAF Submerged Aeration Filtration firmly in the spotlight
This article was originally published on Processingtalk on 9 Apr 2008 at 8.00am (UK)
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As wastewater treatment is a major element of sector power consumption, the highly-efficient HSAF system, with minimal air and power requirements, will make it a technology of considerable interest.
The Brightwater HSAF process is designed to enable BOD and/or ammonia reduction, depending on its configuration within the overall wastewater plant treatment processes.
In most applications, treatment streams are fed through the base of the packaged unit to an aerated biological treatment zone containing the advanced Brightwater BMax media.
Here, wastewater flows upwards through the buoyant recycled plastic media, whose contoured surfaces host a high concentration of active bacteria that reduce BOD or ammonia levels as required.
The air supply that feeds the biological process is distributed evenly throughout the tank via an air grid at its base - this efficient oxygen transfer system means less air is used and less power is required than in standard systems.
The efficiency of the oxygen transfer enables transfer rates of 8 to 10% per metre of tank depth compared to 4 to 5%/m in a standard structured media plant.
The cleaning cycle consists of an air scour and one or more simple desludge stages.
The air scour phase passes additional air through the media, creating turbulence and gently fluidising the media for around ten minutes at intervals of typically between two and seven days, thus releasing the excess solids and biomass.
The reactor then undergoes a settlement period with the air turned off, so that the media bed can repack and the solids collect at the base of the reactor.
The excess solids are then removed from the base before the reactor is put back online.
This procedure maintains media bed hydraulic capacity and enables retention of the biomass, which is needed to ensure treatment efficiency is maintained.
The Brightwater HSAF tank has a compact construction, and the low energy input ensures that system has very low carbon and physical footprints.
Cost comparisons with other equivalent technologies reveal that many rival processes have much higher power requirements.
For instance, a conventional structured media system has a power requirement of 3.7kW at 300mbar of air pressure, whereas the power requirement for the HSAF at the same pressure is just 1.5kW, and the cost per annum for process air at 11p/kwh is GBP1445, substantially less than the GBP3565 energy bill for the structured media system.
This would result in a GBP42,400 saving over the typical 20 year life of such an asset.
The figures for an alternative random media SAF are 3.5kW and GBP3372 per year, giving a GBP38,540 saving over 20 years with a Brightwater system, with similar results for mineral media SAF systems.
In addition, power to provide scour air for backwashing in the HSAF costs just GBP5.68 a year as the buoyant media can be fluidised to release excess solids with minimal additional air.
In terms of performance, the HSAF system also outshines rivals despite its modest power use.
It reduces BOD and ammonia levels in wastewaters using the versatile static bed biological process and BMax floating media, whose high specific surface area (700m2/m3), is more than three times that of structured media systems, which generally provide a surface area for treatment of around 200m2/m3.
The exceptional surface area enables the BMax media to retain a high bacterial population, which in turn facilitates higher BOD loadings of 2.3kg/m3 to achieve a 20mg/l BOD standard, compared to 1kg/m3 for a structured media system.
Focusing on the other removal option for the system, the ammonia loading rate for 5mg/l is 0.3kg/m3 compared to a far inferior 0.08kg/m3 in a structured media system.
Despite the HSAF system low power requirement and tiny footprint, this rich bacterial environment means the system is able to produce high-quality effluent containing just 1mg/l of ammonia in tertiary mode.
Performance data from a range of plants in operation shows that suspended solids of less than 15mg/l at the 95 percentile can also be readily achieved at flow rates of up to 6m3/hr.
The Brightwater HSAF technology is well proven, with over 40 units installed in both municipal systems and non-municipal applications such as landfills.
The filter is available in a range of package plant sizes from 1m2 to 12m2, all with a reactor depth of 2.5m, to treat flows from 3litres/sec to 20litres/sec.
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