Small Scale Testing vs. Full Scale Testing

Small Scale Test vs. Full Size Field Trials for Wastewater Treatment Products
Why Beaker-sized Trials Are Not Good Indicators of Product Performance

By Ned T. Barden, PhD

Over the last few years commercially-available microbial and enzyme remediation products have become increasingly popular for industrial and food preparation wastewater treatment. These biological products have permitted the successful clean-up of a myriad of organic compounds and waste found in many different types of wastewater. When used properly, the best of these products have been highly effective and economical.

In many instances contaminated wastewater has been cleaned up enough to be safely and legally discharged directly into the environment or to the municipal wastewater treatment system.
In food preparation facilities, drainlines remain free of waste blockages and back-ups.
Often utility bill surcharges, due to excessive waste loads as measured by
Biochemical Oxygen Demand (BOD), Total Suspended Solids(TSS), and Oil and Grease (O&G) levels in the wastewater, have been substantially reduced.

As with all new technology, end users want to be assured of the efficacy of the product before buying. Even with a proven tract record, i.e. successful results in previous applications for other customers, a product must often be proven all over again with the next user. In many cases the potential customer himself will want to "try the product out" on a small scale before committing to the sale.

Unfortunately, these hastily set up "small scale" trials do not come close to real world conditions. They are too small, not scientifically set up, and will not stand a chance to duplicate the successful results of previous, full scale field trials. Most often, the small-scale test consists of a beaker or jar with a sample of the waste, e.g. a scoop of fat from the surface blanket found in a grease trap, with a portion of the product to be tested mixed in. After a few days on someone's desk if the fat has not disappeared or been emulsified in the water the product has "failed".

In actuality, these beaker scale tests only favor high surfactant (detergent) or enzyme-only products. A surfactant does not digest the waste, it just emulsifies the fat, i.e. allows it to mix or disperse into the water phase. In a beaker this gives the appearance that digestion is taking place when it really isn't.

In a full-scale wastewater system most of this surfactant treated, emulsified fat would wash through and cause problems for someone else downstream. Wastewater treatment facilities have enough problems without more surfactant-carried grease clogging their lift stations and equalization tanks.

Enzyme-only or bacteria-only products also cause problems downstream. With these treatments, fats and oils are only partially digested, allowing them to mix with water. Downstream the resulting undigested material will cause problems worse than the original fat and oil ever could, forming a very sticky, insoluble coating on every surface it comes in contact with. The coating builds up and entraps other solids, eventually leading to odor problems and restricted flow, complete line blockage, or pump and valve failures.

The best products for wastewater treatment are bacteria-enzyme combination products, such as the BZT™ Waste Digester product line developed by United-Tech, Inc., Tulsa Oklahoma. These proven performers are "full service" degraders and use only GRAS listed microorganisms that have not been genetically altered, plus digestive enzymes selected for high activity in a wide range of wastewater treatment situations. The enzymes initiate the digestion of the organic waste, and the bacteria complete the digestion. By using the partially digested waste as food to grow and multiply, the actively metabolizing bacteria excrete harmless carbon dioxide and water. Most of the organic waste is fully digested "on site" and not sent on to cause problems downstream.

An effective combination product must also contain selected bacterial strains with the ability to grow and establish a digestive biofilm on surfaces throughout the wastewater system. To form a functional biofilm the bacteria need adequate nutrients, physical conditions (pH, temperature, dissolved oxygen), and time. It is the actively degrading bacteria in the biofilm that will provide on-going digestion of the organic waste and keep the system free of blockages and back-ups. Fats and oil are reduced along with BOD and TSS, the factors used to assess surcharges by the local wastewater treatment facility.

Knowing what it takes to establish the active cultures in a system, the best evaluation for efficacy of these treatments are full-scale field trials under actual conditions. Beaker trials cannot duplicate the necessary conditions and cannot meet the minimal requirements of the bacteria-enzyme combination products. Thus, tests performed on a small scale are not reliable indicators of a product's true potential. The nutritional factors, the physical parameters, and the time requirement can be met only under actual full scale field conditions.

A proven tract record from a full scale, real world situation will always be more realistic and reliable than any results poured from a beaker. It is also more economical to use an effective, proven bacteria-enzyme combination product than paying less for one that contains a large number of ineffective bacteria. Beware of products sold by numbers of bacteria only. Choose your wastewater treatment product on the basis of proven performance in full-scale situations, not just because it shows some results in a beaker test or perhaps has the highest count.

Dr. Barden is an applied microbiologist with over 25 years experience in university research, product development, waste treatment, and President of Applied BioResources, Inc.