Troubleshooting Aerated Stabilization Basin
Aerated Stabilization Basin (ASBs) performance can be associated with numerous root causes, both chronic and intermittent. The three main conditions leading to loss...
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Activated Sludge Systems (2)
Filamentous Bacteria Identification
Useful Tool or Red Herring
Mike Foster, Principal Consultant – EBS
Paul Klopping, Principal Consultant – Callan & Brooks
Filamentous 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.
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.