We have received recommendation from our safety vendor to install charcoal slow sand bed filtration system. The purpose of this system will be only to contain or to trap the pathogenic microbes from the bioprocess lab wastewater. Currently our bioprocess lab waste water (almost 90%) is being steam autoclaved and been sent to our ETP facility through underground drain pipes. The filter shall be placed close to bioprocess lab since our ETP facility is located around 500 m from our bioprocess lab and the autoclave may not be always 100% efficient and may pass microbes to ETP. Also there is a possibility of leakage of pathogenic waste water to atmosphere thriugh the underground pipes.
We are not completely convinced about the recommendations and have the following two main doubts:
1) In the recommendation, alternate layers of charcoal and sand have been suggested for the filter. Both charcoal and sand have sizes in mm whereas pathogenic microbes have sizes in microns. How can the filter contain the smaller size pathogenic microbes?
2) In several literature, charcoal has been told as the breeding base material for bacteria. Our lab waste water flow is intermittent. This may cause bacteria to breed on the charcoal layer which could cause more bacteria in the treated water than in feed waste water to the filter. Also, many of the papers in literature don't recommend charcoal layer in slow sand bed filters.
3) The slow sand bed filters are mostly used to purify the lake/river water to drinking water where the turbidity and wastewater feed characteristics are more or less same. Our bioprocess lab wastewater has high turbidity (around 40-60 NTU) and characteristics also vary based on the different experiments performed at different times.
Based on the above points we think that this system will not be adequate to contain/trap the microbes from bioprocess lab wastewater. Please let us know your replies and any suggestions for alternate scheme for containment of microbes.