Most gaseous emissions from wastewater treatment systems, which comprise several gases besides ammonia and hydrogen sulfide, including various VOC’s, are highly malodorous (although some, like methane, are odorless). Not only are these foul smelling gases offensive to workers and neighboring communities, but they are harmful to human health. This is why they are the subject of environmental regulations. This presentation will focus primarily on two of the most frequently encountered culprits, which as mentioned before are ammonia and hydrogen sulfide.
There are essentially three approaches currently being used in an attempt to curb the generation of the foul-smelling and toxic gases we have mentioned. The first is the use of non-biological solutions, such as chemical agents which attempt to provoke chemical changes in the wastewater in order to absorb or oxidize the gases being produced, or filters such as beds of activated carbon or wood chips, in some instances, with the same objective. This solution tends to be of limited usefulness and efficiency and is frequently quite expensive and complicated to maintain.
A second common approach is the application of active biocatalysts. Strains of mutant bacterial cultures are added in the expectation that the organics will be digested more efficiently and thus a reduction in gaseous emissions will be experienced. Synthetic enzymes are sometimes used with the same reasoning.
The third approach is the application of non-active biocatalysts as OrTec, which simply prevent the generation of the offending gases in the first place. For this and other reasons, as we will discuss further on, this is by far the most effective, economical and therefore preferred approach.
As mentioned before, the problem with the first approach is that the hardware and structures required are usually expensive, have large footprints and be hard to maintain; in addition, their efficiency is frequently wanting. In the case of chemicals, the reactions involved tend to produce toxic byproducts that pollute the waste stream discharge, thus causing more problems than they attempt to solve. In the case of biocides, which are used in an attempt to kill all the bacteria involved in the odor-producing process, they wind up also destroying beneficial microorganisms in the receiving bodies, be they rivers, streams or lakes. Although initially this might appear to be a more economical solution, upon more detailed analysis and comparison with other options, this turns out not to be the case. Thus, this is really not a sound approach.
Active biocatalysts don’t share the disadvantages of the non-biological solutions, but they have some serious shortcomings of their own. Specialized, mutant bacterial cultures have been developed over the years, as well as synthetic enzymes, in an attempt to supplant or enhance the biological action of the existing biomass or native microorganisms in any given situation. The idea here is to substitute the native bacteria with more efficient strains, or complement the enzymes produced by the native bacteria in an attempt to accelerate the rate of degradation of the organic matter, thus getting rid of the offensive odors and resulting in a faster and more efficient treatment of the wastewater.
In the first place, in order to achieve the desired results, very large quantities of these biocatalysts must be used, since there are trillions and quadrillions of native bacteria already present in any regular sized treatment system. The addition of a few million new ones is going to have very little effect. Secondly, the new bacteria tend to be very sensitive to brusque changes in their environment, such as pH or organic overloads. They also have relatively short reproductive lives.
Similarly, the addition of very large quantities of enzymes is required to effectively catalyze the biological digestion process. In short, this would lead to unacceptably large expenditures. There are, however, no toxic byproducts resulting from the use of these biocatalysts.
Non-Active Biocatalysts, which don’t contain microorganisms or add enzymes to the biomass, are used in very low concentrations, typically sub-ppm proportions ranging from 0.1 to 1.0 ppm. They are infinitely more efficient that active biocatalysts and chemicals, since they produce a tremendous acceleration of the biological process by which the native microorganisms bring about the digestion of organic matter. This is accomplished by accelerating, or catalyzing, the cellular metabolism of the existing biomass. As a result, they are less expensive than chemicals, filters and active biocatalysts. Rather than upsetting the naturally existing microbial cultures, they squeeze the maximum potential out of them.
The non-active biocatalysts accomplish this task by stimulating the growth of the existing biomass and promoting its purification and acclimation.
Due to their very nature, they are very simple to apply. More importantly, they are completely safe, harmless to workers, and will not produce harmful or toxic byproducts in the treated discharge. They are by far the most efficient, safe, green and economical solution.
Over 15 years’ experience with the application of non-active biocatalysts to hundreds of different applications, commercial, institutional, agricultural, industrial and domestic, have shown us that this is the most effective technology, not only for controlling offensive and unwanted odors, but for eliminating contaminating gases and bringing various situations into regulatory compliance.
These situations can involve not only malodors, but exit parameters as well. This experience includes a wide range of hog, chicken and cattle farms, but also food processing plants of a diverse nature, bakeries, grease traps, wastewater treatment plants (both aerobic and anaerobic) and many others too numerous to mention in this presentation.
It is hard to overemphasize the many favorable characteristics of the non-active biocatalysts. They are usually of vegetable origin, so they are completely “green” and “safe” to handle and apply, not just “safer” or “greener”, as many active biocatalysts are labeled. Our experience is that the non-active biocatalysts end up substituting products that by and large are either completely or partially toxic, or that result in toxic byproducts, and that are not nearly as effective or economical to apply.
These biocatalysts are non-active, in other words they do not have active ingredients as such and contain no bacteria, and thus are non-toxic to any living being. They are also extremely concentrated and this is why they are applied in sub-ppm proportions.
Since their effect is on the indigenous bacteria, they can be applied in aerobic, anaerobic or facultative systems, with the same effects. This includes digesters, activated sludge systems, lagoons and ponds, septic systems and many others.
When dealing with aerobic reactors with areators, spargers and the like, mixing is usually not an issue, since the turbulence will provide the necessary homogenization. When stagnant ponds or lagoons are involved, on occasion some means of mechanical mixing might be required in order to accelerate the results and the effectiveness.
Corrosion is frequently an important factor in anaerobic digesters or reactors, so the elimination of gases such as hydrogen sulfide provide an additional cost incentive due to reduced equipment maintenance. If methane is recovered, the cost of applying the products is completely recovered and frequently they produce substantial additional profits from the extra energy.
These non-active biocatalysts have also been used with complete success to treat solid waste in various settings.