A majority of industrial sites emit hazardous toxic substances like ammonia and hydrogen sulphide that are immensely harmful for the human body. These toxic substances are generated due to processing of industrial products like leather, chicken sheds and food processing. These harmful matters are generally released into the water, and air, and if this is untreated for a long time, it generates odour that cause long time health issues. Nowadays, modern odour control technologies like Biofilters are considered to be effective in odour treatment. There are certain aspects that make this particular system effective in controlling industrial odour.
What is Bio Filtration?
Bio filtration is a process that involves the movement of contaminated air stream through a media bed that is porous and moist. As this air passes through the media, the toxic substances are absorbed in the water. The water in the media contains micro organisms like bacteria which act as a catalyst in the whole process. The absorbed contaminants are consumed by bacteria. This helps in a clean emission of air.
There is a different process in which the air containing odour is passed directly through a medium containing lava rocks, which is extremely porous. The rocks create adequate space for the bacteria to settle down and hence this process eliminates the toxic substances from the air effectively. The bio-filtration process reduces 80 to 95 % of the toxic substances. There are three specific characteristics of this particular system. They are:
• Either Open or enclosed
• Built on the ground or inside a reactor
• Several or single bed
There are various kinds of reactors in which the bio-filtration process takes place. The major ones are:
a) Bio trickling filters – In bio-filtration process, hydrogen sulphide is absorbed and the sulphur molecules stays back in the media. This happens due to the oxidation process. The sulphuric acid that is left behind gets accumulated in the filters thus hampering the filtration process to a great extent. The bio trickling filters were developed in order to restrict this issue. This is actually a type of bio-filtration process that uses multi layer system. In this system, plastic media is used and, the distribution of water and air are done through various layers. This increases the activity of microbes that are attached to the media. High load of toxic substances like hydrogen sulphide and ammonia are effectively treated in these particular types of filters.
b) Bio scrubber –This bio-filtration process is now widely used because of its capabilities of reducing maximum odour out of a bulk emission. A separate vessel full of microbes actually performs the absorption process. This is much more effective than the other processes because it reduces the contaminants in a sequential process.
Bio filters involve two kinds of mediums that work effectively in order to absorb the toxic substances. Peat, compost and wood chips, form the first basic media, whereas, the modern media consists of plastic. The whole process has a higher initial cost but, at the long run this particular odour control system proves to be effective.