A comparison of Plastic MBBR/IFAS Technology with Levapor Technology
Material of Construction
HDPE : virgin /Recycled/PP/PVC
Poly Ether based Poly Urethane
The properties of HDPE are more often fixed and can not vary/modify to meet requirement for particular application. While PU properties are highly variable and can be modified to meet the properties required for individual application
Due to hydrophobic nature of HDPE plastic, it offers poor water affinity to water and thus biofilm development in wastewater treatment application requires significant time. While Poly Ether based PU are hydrophilic in nature and thus biofilm development is very fast compared to HDPE.
Hydrophilic nature of the PU material also helps in better fluidization of the moving carrier bed and wetting takes place at very faster rate compared to HDPE.
Very high due to impregnation of PU foam matrix with 15-50 kg highly adsorbent activated carbon per m3 of foam
Adsorbent capacity of carrier material is very important property as adsorbent capacity provides , faster adherence of micro organisms on the carrier surface and also adsorbs toxic pollutants on the carrier material which then can be biodegraded by micro organisms causing reversible regeneration of the adsorbing surface.
Levapor carriers are impregnated with activated carbon which provides very high adsorbent capacity rendering remarkable faster colonization of the carrier material, adsorption of toxic material and their degradation which offers far better process stability due to reduction of toxic pollutant concentration in the bulk liquid and its subsequent degradation
On the contrary plastic carriers offer no adsorbent capacity and thus the advantages offered by adsorbent surface are not available with plastic carriers and MBBR/IFAS processes.
Due to the fine pore structure of PU foam matrix, Levapor carrier offers very high internal porosity. The high internal porosity allows for better substrate and DO gradients in the carrier material offering ideal habitat for Nitrifying bacteria and other slowly growing micro organisms which requires varying substrate/DO conditions compared to micro organisms growing in bulk liquid with higher substrate/DO concentration.
The internal porosity also allows for growth of micro organisms in films as well as discrete micro organisms adhering to the carrier material preventing their complete wash our against excessive shear conditions due to mixing and aeration requirement.
Levapor carriers have porosity of 40 pores per inch of carrier length allowing for easy transport of a particle of 370-450 micron through it rendering self cleaning ability and better transport of particulate substrate in it.
The plastic carrier material is highly dependent on the shape of the carrier for its internal porosity and not much internal porosity is offered per m2 effective surface area.
600-650 m2/m3 effective surface area
The effective surface area offered by plastic is 600-650 m2/m3 while un modified PU foam has a surface area of 2500 m2/m3 but the impregnation of PU foam with activated carbon results in surface area as high as 20,000 m2/m3.
The higher amount of surface area results in more amount of micro organisms per m3 of media provided and requires lower degree of filling.
100-150 kg/m3 (general data as no information available from Aqwise)
The bulk weight of plastic carriers due to HDPE material would be very high requiring additional amount of energy for mixing and fluidization while the PU based Levapor carriers have weight of 25-45 kg/m3 which requires quite less amount of energy for mixing and fluidization reducing the energy consumption of the plant to a significant level. Even the colonized Levapor carriers have weight in the range of 65-80 kg/m3 which is nearly 30-50% lower than the HDPE based plastic carriers.
Due to higher surface area to volume ratios , the degree of reactor filling required for Levapor carriers is less compared to plastic carriers resulting in smaller foot print, lower energy consumption.
It also reduces the media requirement for particular treatment resulting in lower capital costs.
The lower degree of filling also enables significant amount of biomass growth in the suspended phase making the reactor truly hybrid in its configuration.
Bulk DO concentration
Due to the surface geometry and film thickness plastic carriers based MBBR/IFAS reactors require to operate at higher bulk DO concentration of 3-5 mg/lit to facilitate better transport of DO within the internal parts of film.
While due to fine pore structure and thus film geometry , Levapor based MBBR/IFAS reactor can be operated efficiently with bulk DO concentration of 2-3 mg/lit resulting in lower aeration requirements and thus lower energy consumption for the required treatment.
Simultaneous Nitrification – Denitrification
Observed lower Total Nitrogen Leaving the reactor
have observed lower nitrogen concentration leaving the Levapor based reactor which could be contributed to simultaneous nitrification-denitrification due to anoxic conditions prevailing in the internal pores of the carrier material resulting in lower Total –N concentration and thus if configured for Pre-Anoxic denitrification then lower recirculation of nitrates required for complete nitrogen removal.