Types of operations in treatment facilities with the using of microorganisms

Lectures 4-5

Bacteria may be aerobic, anaerobic or facultative. Aerobic bacteria require oxygen for life support whereas anaerobes can sustain life without oxygen. Facultative bacteria have the capability of living either in the presence or in the absent of oxygen. In the typical sewage treatment plant, oxygen is added to improve the functioning of aerobic bacteria and to assist them in maintaining superiority over the anaerobes. Agitation, settling, pH and other controllable are carefully considered and employed as a means of maximizing the potential of bacterial reduction of organic in the wastewater.

Single-celled organisms grow and when they have attained a certain size, divide, becoming two. Assuming an adequate food supply, they then grow and divide again like the original cell. Every time a cell splits, approximately every 20 to 30 minutes, a new generation occurs. This is known as the exponential or logarithmic growth phase. At the exponential growth rate, the largest number of cells are produced in the shortest period of time. In nature and in the laboratory, this growth cannot be maintained indefinitely, simply because the optimum environment of growth cannot be maintained. The amount of growth is the function of two variables: - environment and food. The pattern which actually results is known as the bacterial growth rate curve. Initially dehydrated products (dry) must first re-hydrate and acclimate in a linear growth phase before the exponential rate is reached.

Microorganisms and their enzyme systems are responsible for many different chemical reactions produced in the degradation of organic matter. As the bacteria metabolize, grow and divide they produce enzymes. These enzymes are high molecular weight proteins.

It is important to recognize the fact that colonies of bacteria are literally factories for the production of enzymes. The enzymes which are manufactured by the bacteria will be appropriate to the substrate in which the enzyme will be working and so you have automatic production of the right enzyme for the biological reduction of any waste material, provided you have the right bacteria to start with. Enzymes do not reproduce whereas as bacteria do.

Enzymes in biochemical reactions act as organic catalysts. The enzymes actually become a part of the action, but after having caused it, split off from it and are themselves unchanged. After the biochemical reactions are complete and products formed, the enzyme is released to catalyze another reaction. The rate of reaction may be increase by increasing the quantity of the substrate or temperature up to a certain point, but beyond this, the rate of reaction ceases to increase because the enzyme concentration limits it.

All treatment plants should be designed to take advantage of the decomposition of organic materials by bacterial activity. This is something you can equate to lower costs, increased capacity, and an improved quality of effluent; even freedom from bad odors which may typically result when anaerobe bacteria become dominant and in their decomposition process, produce hydrogen sulfide gas and similar by-products.

Consider the fact that the total organic load of wastewater or sewage is composed of constantly changing constituent, it would be quite difficult to degrade all of these organics by the addition of one enzyme, or even several enzymes. Enzymes are specific catalysts and do not reproduce. What is needed is the addition of an enzyme manufacturing system right in the sewage that can be pre - determined as to its activity and performance and which has the initial or continuing capacity to reduce waste.

At the present time, the addition of specifically cultured bacteria seems to be the least expensive and most generally reliable way to accomplish desirable results. When you add the right bacteria in proper proportions to the environment, you have established entirely new parameters of potential for the treatment situation.

The use of microbes in wastewater treatment plants is well documented and is an integral piece of the wastewater treatment process. However, due to various circumstances, the natural microbial population in a facility can become depleted resulting in system back-ups, organic material build-up and overall reduction in system efficiency. It is at this point when supplementation of a microbial product becomes necessary.

Traditionally, microorganisms are used in the secondary treatment of wastewater to remove dissolved organic matter. The microbes are used in fixed film systems, suspended film systems or lagoon systems, depending upon the preference of the treatment plant. All of which are stages that microbial supplementation can be added with benefit. A higher concentration of microbes is going to be able to more quickly remove the organic matter from the water, particularly in the case of lagoon systems where it can take several months for the degradation of waste to be completed.

Microbes also can be of benefit in other stages of the process. Microbes added into the primary treatment phase can work to degrade bottom and surface solids, resulting in less production of sludge. Implementation here can cause the secondary treatment phase to be even more effective through a more thorough treatment in the primary phase.

In some wastewater treatment plants, an advanced treatment stage is necessary to remove excess nutrients that can result in algal blooms and other downstream issues. Microbes can be substituted for chemicals in this stage to keep the treatment process as natural as possible and minimize further pollution.

Finally, the addition of microorganisms can prove beneficial in reducing the volume of sludge that must be disposed of. As a byproduct of the wastewater treatment, sludge is filtered out throughout the various treatment stages and must be treated before disposal. Microbes aid in the treatment and disposal of the sludge by decomposing additional organic matter and reducing volume, while also limiting the noxious odors emitted by the sludge.

It is not hard to see why so many wastewater treatment plants are using biological alternatives in their systems. Aside from the benefits of improved capacity, improved efficiency and lowered operation costs, microbes also keep the treatment process as natural as possible, which is the ultimate goal of a wastewater treatment plant.

Control questions:

1. How do microorganisms help in sewage treatment plant?
2. Which microorganisms can be use in sewage treatment plant?
3. Define the following: Biosorption, bioaugmentation, biofiltration, bioleaching?
4. What do you understand by the terms ‘in situ’ and ‘ex situ’ conservation? Discuss the different approaches used for in situ and ex situ conservation of plant and animal species in different parts of the world.

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