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biochemical oxygen demand, filamentous bacteria, biochemical oxygen demand bod, chemical oxygen demand

Features of a Wastewater Microscopic Evaluation

MicroscopeThe purpose of a microscopic evaluation is to determine the biological health of a wastewater treatment system. The results can be used to help predict Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), TOC, and TSS results or to determine whether or not to supplement the system with nutrients or bacteria after an environmental upset. The results will also help to determine the degree of toxicity caused by an upset condition.

The biological health of a wastewater system can be determined microscopically by observing several features of the samples. Floc is an aggregation of bacteria that produce a polysaccharide coating which enables them to adsorb to chemical contaminants, which they will later degrade for food, and to adere to each other.

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floc, aeration, filamentous bacteria, abundance, heterotrophic organisms, Aerated Stabilization Basins, filament, activated sludge, aerator, filamentous organisms, aeration basin, effluent, carbon compounds, filaments

Filamentous Bacteria in Aerated Stabilization Basins Part 2

Concern or Curiosity?

Part 2 – Thiothrix and Type 021N

Mike Foster, Principal Consultant – Environmental Business Specialists, LLC
Paul Klopping, Principal Consultant – Callan & Brooks

ThiothrixIn part one of this series, we discussed the differences between activated sludge and aerated stabilization basins (ASBs) with regard to filamentous bacteria and filamentous bulking. We also talked about one of the most common filaments found in ASBs, Haliscomenobacter hydrossis. In this article, we will discuss three other filament species found in aerated stabilization basins – Type 021N, Thiothrix, Beggiatoa.

These three filaments all share a common metabolic trait – mixotrophy. These organisms can grow on a number of organic compounds heterotrophically, but also may gain energy for growth from the simultaneous oxidation of inorganic, reduced sulfur compounds (e. g. H2S). Thus the presence of reduced sulfur compounds in wastes being treated may give these filamentous organisms a growth advantage over other strictly heterotrophic organisms (i.e. floc formers). It should be noted that actual energy capture from sulfur oxidation has not been vigorously proven, as yet, and that true autotrophy does not occur, as organic carbon compounds are always required for growth.

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Activated Sludge Systems, deeper understanding, filamentous bacteria, daigger, growth pressures, conventional wisdom, michael richard, laboratory conditions, david jenkins, filaments

Filamentous Bacteria Identification

Useful Tool or Red Herring

Mike Foster, Principal Consultant – EBS
Paul Klopping, Principal Consultant – Callan & Brooks

Filamentous bulkingFilamentous bulking is a major problem for operators of municipal and industrial activated sludge systems. For the past thirty years, renowned scientists, such as Dick Eickelboom, David Jenkins, Glenn Daigger, and Michael Richard have written extensively about the identification of the various species of filamentous bacteria and their probable causes. Because these filaments generally cannot be grown in pure cultures under laboratory conditions, most of the causative assignments regarding filamentous bacteria are empirical in nature.

Conventional wisdom says that filamentous bacterial abundance is a function of several principle causes – low dissolved oxygen, low nutrient residuals, high sludge age (low f:m), readily metabolized substrates (organic acids or starches), and sulfides. The problem arises from the fact that very few filaments can be assigned to only one cause and (as mentioned above) the causative relationships for filaments are almost entirely empirical in nature.

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Activated Sludge Systems, continuous operation, lagoon system, Biological Treatment, industrial wastewater, Aerated Stabilization Basins, activated sludge system, cold weather, carbon source, aeration equipment, clari, inorganic matter

Pros and Cons of Aerated Stabilization Basins and Activated Sludge Systems

In North America, there are predominantly two systems used to biologically treat industrial wastewater: the aerated stabilization basin (ASB or aerated lagoon) and the activated sludge system. These two systems have far more similarities than differences. Both pro ­cesses are based on the utilization of dissolved oxygen by microorganisms in converting organic and inorganic matter into a settleable form. The following provides information on the pros and cons of each system.

Aerated Stabilization Basin – Figure 1

The ASB, also known as a lagoon system, is a large body of water used for biological treatment. The placement and continuous operation aeration equipment is both the most important part of the system and the most expensive. Untreated effluent comes into the primary clari­fier and then into the ASB. As the effluent passes through the system, the BOD or “food” present is used as energy and a carbon source for bacteria. Once the treated water has gone through the ASB it typically enters a polishing pond for tertiary treatment where the remaining TSS (total suspended solids) settles out before being discharged as the final effluent.  These systems are particularly widely used in the pulp and paper industry in the southeastern United States, where mills are usually remote and have access to large tracts of land.

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