Activated sludge describes a wastewater treatment process in which the microbes that grow on the contaminants in the wastewater are recycled; i.e., they stay in the system.
By maintaining a higher population of active microbes or biomass, the treatment time required to reach removal goals is shortened. In addition, the microbes are acclimated to the composition of the wastewater and “selected” or enriched in the microbes that are most efficient.
There are quite a few variations in the design of activated sludge systems. The simplest consists of an aeration tank and a clarifier.
Microbes grow in the aeration tank and settle to the bottom of the clarifier. The concentrated suspension of microbes is partially returned to the aeration tank (return activated sludge or RAS) and partially wasted (waste activated sludge or WAS) so that the concentration of microbes is relatively constant in the aeration tank. The amount wasted is approximately equal to the amount of growth or increase in the amount of biomass.
Many plant designs have additional modifications for processes, such as:
As noted above, increasing the biomass concentration (the mixed liquor suspended solids or MLSS) in the aeration tank increases the rate of contaminant removal and thus allows a smaller tank to achieve the treatment goals. To that end, a variety of plant designs attempt to do this.
Another strategy to keep a high biomass concentration in contact with the wastewater is the use of plastic media. It’s used in trickling filters, rotating biological contactors (RBC), submerged fixed film bioreactors and moving bed bioreactors (MBBR). Media allows the majority of the microbes to attach and thus stay in the aeration tank. Additional biomass may be returned from the clarifier.
Activated sludge processes may experience a variety of problems:
No activated sludge plant design is exactly the same, which means the problems you may encounter are unique. You need a wastewater treatment plant expert to diagnose your plant’s issues and offer an effective solution.
Monera Technologies provides expert technical assistance to diagnose and treat the problems occurring in wastewater treatment. Contact us for bacterial and nutrient products to aid in the correction of treatment deficiencies in your activated sludge plant.