Bacterial Biology Discussion
Bacteria, along with other organisms, are responsible for the breaking down of organic waste, and an understanding of their characteristics is critical to pollution control technologies. In discussions of WWTPs the terms “bugs” and “bacteria” are generally used to describe the organisms involved in biological activity. In our discussions we are only talking about bacteria. Another term used in biological treatment is enzymes, which are non-living chemicals produced by bacteria that help break down organic waste into a form more easily consumed by bacteria. Enzymes are catalysts that assist in conversion of material, but aren’t consumed in the process. Some bacteria produce enzymes. There are thousands of different enzymes produced by bacteria. Enzymes, or more accurately exoenzymes, are manufactured by common bacteria when their food source is limited.
Viruses are the lowest life form, and are many thousands times smaller than bacteria. Bacteria are single cell organisms between 1 – 5 microns in size. Bacteria have a cell wall, with no internal organs or body parts, and can be many shapes. Bacteria are too small to be identified or studied in an optical microscope, but can be studied with an electron microscope.
A sample of various bacterial shapes is shown below. Please remember that the size ranges from about 1 to 5 microns.
Higher life forms involved in biological activity in water include protozoans, worms, and rotifers, and are over 1000 microns in size.
Bacterial cell walls have many pores that can absorb soluble material. They can’t consume particles, and absorb food through somatic pressure. Material with a molecular weight of 1000 or less, and only soluble material like sugars and amino acids, can pass through cell walls. Colloidal material such as milk proteins, starches, and fats can’t pass through pores, but can be converted to soluble material with enzymes.
The solubilization of material represents about 50% of the ESI WWTP business.
The classification of bacteria is constantly evolving. For our purposes bacteria that are active within a moderate temperature range are the classes of bacteria we deal with.
45 C – Mesophilic bacteria: Bacteria and temperature range we can have commercial application (10 to 40 C).
10 C Freezing Point
1. Anaerobic – absence of oxygen, some bacteria can’t live with dissolved oxygen.
2. Facultative – with or without dissolved oxygen, many bacteria in this class, use SO4, NO3, etc. as oxygen source to replace dissolved oxygen.
3. Aerobic – with dissolved oxygen, most common classes for our application.
Bacterial reproduction is a key element to the successful technologies and products available through ESI. The selection of specialized bacteria and the control of reproduction within unique bioreactor environments enable ESI products to be manufactured for a variety of applications.
Bacteria reproduce at varying rates, from several minutes to many hours. Typical bacteria reproduce every 30 to 60 minutes in an adequate environment. Even this difference in reproduction rate matters significantly over a given time as presented in the table below.
All organisms compete for energy and material. In wastewater treatment it is important to efficiently break down organic material using very small organisms, largely made up of bacteria. This is the basis of secondary treatment. Generally the better the bacteria can multiply the more successful they will be in a given environment. However, in order to breakdown specific kinds of material, specialized bacteria may be necessary. These specialized bacteria can be a specific type of bacteria, or can be specially conditioned common bacteria.
Another aspect of bacterial biology that plays an important role in our technologies is the performance and reproduction of nitrifying bacteria. Nitrifying bacteria play an important role in reducing ammonia and nitrite levels in aquariums and in the effluent of a wastewater treatment plant, and in the control of excessive algae growth in ponds. Because nitrifying bacteria closely resemble algae in their food source requirements the addition of these specialized bacterial types into ponds experiencing algae blooms can be an effective algae reduction program. Excessive algae can result in depletion of dissolved oxygen as algae matter decomposes, the build up of organic sediment, high suspended solids, and odors.
Nitrification is basically the conversion of ammonia (NH3) to nitrite (NO2) and then to nitrate (NO3). NH3 is quite toxic to fish and other aquatic organisms, NO2 is less toxic, and NO3 is relatively non-toxic. Nitrification occurs in aerobic and relatively clean, low BOD conditions. BOD is a commonly used parameter to measure the effect of organic matter within one body of water or treatment plant has on the receiving stream’s dissolved oxygen, usually over a five-day period.
While there are thousands of types of bacteria that consume organic matter, there are only ten species of nitrifying bacteria. As such, there are much lower numbers of these specialized bacteria in a given aquatic environment. Two important groups of nitrifiers as they relate to our nitrification technology are:
Nitrosomas, which converts NH3 to NO2, and
Nitrobacter, which converts NO2 to NO3.
Typically there is a pH drop during nitrification as hydrogen ions are released. If alkalinity (a measure of the buffering capacity in the water – carbonate) is high, there is no significant drop. If alkalinity is low, there may be a pH drop.
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