Multiple filter installation for UK water PLC
Southern Water Denitrification Biosand™
The Biosand™ pilot plant
The Biosand™ Internal arrangement
Biosand™. Biomass sand grain attachment in highly active biofilms, resulting in high biological activity Internal arrangement
Biosand™. Active biomass is retained on grains of sand even after the washing process
Aquabio Ltd - Nitrification / Denitrification
AquaBiofilter™ Biofiltration
For wastewater and process water AquaBiofilter™ biofiltration is the perfect match for combining biological conversion and efficient retention of suspended solids. Nitrification / Denitrification form part of the Aquabio's Tertiary Treatment process solutions utilising the AquaBiofilter™ filters.
For a technical presentation on the benefits of using AquaBiofilter™ for nitrification & denitrification, click here. A technical paper describing the application of the AquaBiofilter™ filter can be found here.
Please see our downloads section for further case studies explaining nitrification & denitrification using AquaBiofilter™.
The process is based on continuous moving bed high rate upflow filtration, using fine sand media for achieving both a high area/volume ratio with efficient biomass attachment and a highly efficient deep-bed filtration process. The continuous sand washing process enables a 24 hours per day uninterrupted operation. Filtrate is used for sand washing, therefore the continuous washwater recycle does not contribute to the organic load of any of of the upstream processes. AquaBiofilter™ works as a continuous-process, in which the filter bed is cleaned during the filtration operation, and as a result process interruptions are eliminated. AquaBiofilter™ is self cleaning.
Tertiary Nitrification Using AquaBiofilter™ - Ammonia Removal
Ammonium-nitrogen may be present in municipal and industrial waste water, but also in groundwater. As an oxygen consuming component ammonium levels should be low in order to use the water as process water, or to discharge the water into surface water. Ammonium nitrogen may be converted into nitrogen gas by means of autotrophic bacteria, using oxygen. For ammonium levels up to 20-30 mg/l N this process may effectively be executed in an AquaBiofilter™ bioreactor, using the filter material as carrier material for the nitrifying biomass.
Ammonium Removal - Process
Within the AquaBiofilter™ filter the biomass growth is balanced by the continuous rinsing of the filter media. In this respect it is important to maintain as much biomass within the reactor as necessary for full nitrification. If the feed water quality and quantity shows considerable variations this can be achieved by a continuous control of the sand rinsing capacity.
Ammonium Removal - Oxygen
The required oxygen uptake for the nitrification process can be supplied in different ways. For some applications pure oxygen may be dosed, while for other cases compressed air may be used. The air is distributed homogeneously over the filter area in order to assure an even gas flow rate.
Tertiary Denitrification Using AquaBiofilter™
Final effluent consent levels may be as stringent as <5 mg/l total nitrogen in order to improve the quality of the receiving water and prevent algae blooms. The majority of the secondary works in the UK were not originally designed for full denitrification and hence they need to be upgraded where the new standards apply. It is often difficult to adapt existing works to these new criteria as it requires new, or additional, anoxic stage(s) and high recycling rates (for activated sludge plants) or the denitrification may not be easily integrated into the existing infrastructure (mineral and plastic media filters). As a result tertiary denitrification is implemented using AquaBiofilter™ moving bed biofiltration.
Process set-up
Within the filter anoxic conditions prevail, enabling the denitrifying biomass to grow on top of the grain surface and in the pores of the bed. After passing the filter bed (in upflow mode) the filtrate is characterized by low dissolved oxygen, NOx-N and TSS concentrations. Furthermore a 10-15% decrease in COD means that the carbon source (added prior to the filter) is efficiently taken up. The residual NOx-N is mainly NO3-N (nitrate). AquaBiofilter™ denitrification plants are efficient as well as providing robust and reliable reduction of both total nitrogen and solids. Consistently low outputs of TSS and NOx-N levels of <10mg/l and <2mg/l respectively are achieved. Several AquaBiofilter™ denitrifying filter installations are now in operation, or under construction, in Europe, Asia and Northern America.
Refurbishment and Optimisation of Existing Tertiary Plants
In the past 20 years a vast number of tertiary moving bed filters have been installed to remove suspended solids and BOD attached to solids. These plants were put into place to meet the previous, or current, consent levels. As the new and future consent levels are focusing on even lower levels for TSS, BOD, as well as ammonia, nitrate and phosphorus, it becomes commercially and operationally attractive to investigate any opportunity to easy upgrade existing facilities. This is when it might be possible to modify and refurbish existing ‘standard’ filter plants into biofilters and so combining the functions for TSS removal, nitrification and/or denitrification. Considerable savings can be made as the existing infrastructure is maintained and reused in a second life.
Process Monitoring and Regulation
AMBR / BIOVERT™ For Total Nitrogen Removal
Aquabio's membrane bioreactor technology has been applied for total nitrogen removal in high strength wastewaters. This enables very strict discharge requirements to be met using single and multiple nitrification and denitrification stages. One such plant has been designed and constructed for DEFRA in 2006. For more information please see this case study.