The two most commonly used chemical scrubber designs are packed bed and mist. While considerably different in design and operation, their shared historical purpose is to collect and absorb nuisance malodors into a liquid solution containing water and an oxidant chemical like chlorine, sodium hypochlorite or chloride dioxide as well as pH adjusters such as caustic soda and phosphoric acid so that treatment for hydrogen sulfide and ammonia can occur in the liquid phase.
Bioscrubbers have been historically handicapped by the difficulty of developing and maintaining the bacterial seeding. Nutrients and other additives has been proved quite inefficient.
But with the use of Non-Active Biocatalysts as OrTec the bioscrubbers need less maintenance, less water use and have a longer life and you can easily retrofit chemical scrubbers into bioscrubbers.
Chemical Scrubbers
- Used to absorb the contaminants into an additive, usually in the aqueous phase.
- The contaminant are transferred from the gas to the liquid phase – but not treated
- Removal efficiency is controlled by blow-down rate – high efficiency requires high blow-down rates and creates high levels of BOD (Biochemical Oxygen Demand) in the water blow-down
- May be effective for compounds with high aqueous solubility and low volatility.
- Contaminant is chemically bound in aqueous phase by an additive
- Additives are consumed and have to be added continuously
- Operating cost is higher due to additive costs
- In general additives are hazardous (i.e. Phosphoric Acid, Caustic Soda, Sodium Hypochlorite, etc.)
- Since additive functions only in aqueous phase, contaminants have to get solubilized in water first, before mixing can occur
- Problem also occur with contaminants with low aqueous solubility
Bioscrubbers
- Can treat (not just remove) organics (phenol, toluene, ethanol. methanol, etc.) as well as inorganics, such as hydrogen sulfide, ammonia, etc.
- Organics are converted to carbon dioxide and water
- Specialized packing, is used to allow active biofilms to form on surface and effectively contact contaminant(s) in gas phase
- Non-Active Biocatalysts (without bacterial content) are used to accelerate the biodegradation of the contaminants by the active biofilms
- With the use of non-active biocatalysts large biofilm loadings will not clog the system.
- Bioscrubbers are constructed just like a chemical scrubber (it is generally possible to retrofit them into bioscrubbers), with grating to hold the specialized packing material and liquid nozzles to distribute the recycled liquid
- Bioscrubbers are seeded at start-up using activated sludge liquid, and a non-active biocatalyst maintenance liquid is recycled at low flow rate to keep biofilms moist
With the use of a non-active biocatalyst (www.ortecltd.com) the bioscrubbers need less maintenance, less water use and have a longer life. Additionally this safe and cheap product makes the blow-down to not pollute. In short a green and economical solution.