How do I evaluate Biological products?

Well one thing to note- cfu stands for colony forming units. It is a measure of plate counting bacteria to get official numeration of the amount of bacteria present per gram of product. Make sure the CFU or plate counts are per gram vs. per gallon, per lb, etc.

What you are measuring has to correlate to how you obtained the sample, how much sample is used and how the results were achieved. Sound complicated, well it can be. Sometimes vendors use plate counts as a "magic number" to wave around and try to out maneuver their competitors. Numbers are not always as important as the types of bacteria present.

We have done years of studies that prove that the number of bacteria present is not as critical as the types of bacteria present. We have found in most wastewater treatment facilities, that it is the Gram Negative bacteria that are better floc formers. Bacillus and Gram positive bacteria do not form as solid of a floc structure. Both types of bacteria will degrade BOD similarly. But in most treatment plants, BOD as well as TSS is important, therefore, floc structure is very important.

One thing we did when testing and developing biological products was to perform shake flask tests. Shake flask studies are conducted for treatability studies of wastewater samples to reduce overall BOD or to target a specific compound and to improve settling characteristics. It can be used for toxicity studies or for product screening procedures. It is similar to a quick and dirty jar testing for polymers that most people are familiar with but takes a little bit more time and is used to evaluate the performance of biological products.

These studies use various strains of bacteria and different supplier's products to test counts vs. types of bacteria present. BOD removal, floc formation, higher life forms present, and TSS were all measurements that were taken into consideration. If plate counts are performed, the number of bacteria, the size and shape of the colonies on the plate as well as the diversity must be taken into consideration. Slime formation on the plates should be evaluated also.

*Note- Sometimes if companies are aware that a biological product is going to be used for comparison studies between other companies and competitive biological products, they have been known to "spike " the test sample to a higher concentration of bacteria in order for their product to deliver higher results. Be careful what you tell the supplier or make sure that what sample they deliver meets those same specs continually. Hold them to the plate counts on their biological product if they maintain that this is their normal product quality.

Here is a photo of two sets of plates. One biological product is mostly bacillus or gram positive bacteria. The set on the right is a mixture with a high blend of Gram negative bacteria and mostly pseudomonas. The plate on the right, regardless of the initial counts, showed higher growth potential and activity, more natural polysaccharides, which help to form floc and reduce TSS and polymer consumption in final clarifiers.

Here is a two-week trial of our biological product vs. a competitor product. Our biological products typically  have only a count of 1 billion per gram, but it is mostly gram negative bacteria. Here is a competitor product used at an outside lab in a treatability study. Formula A has a count of 5 billion per gram. This study was run for three weeks.

How do I evaluate  biological products from one supplier to another?
Biological Wastewater Treatment Products
Biological Product Information

The treatability of the wastewater samples is determined on the basis of

• Relative increase in bacterial counts (T_final / T_initial)
• Decrease in TOC and TSS over the 24-hr period.
• Microscopic Examination including:
• Number and morphology of floc structures, color,
• Settleability, size and shape of floc
• Polysaccharide coating
• Quantification of higher life forms- types as well as numbers
• Clarity of the bulk water

Ok, well that was a lab test, sometimes field tests may prove to be different. do you still doubt that bacterial counts are not as important as types? Think of it this way, if you were to chose a basketball team and had 10 guys off the street vs. 5 Michael Jordans- who do you think would give you better results? You do not chose a polymer program based upon actives or molecular count, but on performance, why should you choose your bacterial products based upon numbers?