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Environmental Best Practices, Part 3

(October 2008) posted on Mon Oct 06, 2008

Structuring your company around safe environmental practices is becoming a necessity


By Neil Bolding, Steven Abbott

Chemicals going down the drain must be readily biodegradable, which means that the bacteria are happy to consume them. Readily biodegradable is defined by a set of tests (e.g., OECD 301B, 301D, 301E, 301F, modified Sturm test), which show that a large proportion (>60%) of the solvent is converted into carbon dioxide from the sewage sludge in a short time, typically about 10 days.

In theory one way to reduce BOD in the effluent is to use solvents that aren’t readily biodegradable, but this simply means that the solvents will end up being discharged from the sewage outfall back into rivers and streams. Also, don’t be confused by products labelled as inherently biodegradable, which are significantly less biodegradable than materials classified as readily biodegradable.

 

The effect of waste on bacteria

It should be clear by now that killing off friendly bacteria is not a good idea. What is not so obvious is that the bacterial conversion of waste starts right at your facility. The sewage pipe leaving your operation should be full of friendly bacteria. They are happy to be there because you are providing them with a great source of food. So the journey from your facility to the main sewage-treatment facility provides an opportunity for a large amount of your waste to be consumed, which in turn means that the sewage treatment plant doesn’t need to be as large.

If you’re not careful, however, you can kill off the bacteria along your section of the sewer line. What kills them? If you are throwing buckets of hot water down the pipe, you’re not just wasting precious heat, you’re also killing off bacteria. If you are throwing down lots of bleach or acid or alkali (such as caustic haze removers), then you are also wasting precious chemicals and killing bacteria. Ideally, you should monitor both the temperature and pH (measure of acidity or alkalinity) of your effluent on a continual basis to avoid overloading the bacteria. Most facilities don’t throw down a constant stream of alkali, so spot checks of pH may be enough to tell you whether you’re doing fine.

 

Effect on the outflow


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