What you should know: Everything about wastewater treatment and small sewage treatment plants (4)

After important basic knowledge about #wastewater treatment with #small#sewage treatment plants in parts 1 and 2 of our knowledge series, this part continues with the explanation of conventional #cleaning processes and plant types, before we come to the next and last part to the processes and systems that are " State of the Art" and in times of #climatechange stand for forward-looking water and #climateprotection.

Rotating diving body systems

The #biofilm of the #rotary immersion body system changes between immersed and emerged state, due to the rotational movement of the #growth surfaces - a technical #ventilation device is therefore usually not required here. The cleaning performance is usually limited to #effluent class C (#carbon reduction).

Special system features
The #growing bodies are circular discs that are arranged on a shaft at a small distance from each other. The biofilm forms on the pane surfaces. A prerequisite for this is a constant rotation of the discs, since the biofilm absorbs nutrients when submerged and atmospheric oxygen when it emerges. The waste water is fed into the #bioreactor via a #primary treatment (#settlement pit) in a free gradient and treated there. The cleaned water then goes into the #secondary clarifier, in which #sludge particles from the bioreactor are retained. Excess sludge is conveyed back to the primary clarifier via a mechanical device or a pump.

What are the controls look like?
The operator should ensure that no solids escape from the preliminary treatment. Check that the disks run smoothly and evenly. The statutory controls must be carried out.

Activated sludge treatment plants using the continuous flow principle (BB)

The #activated sludge treatment plant using the continuous flow principle is operated with free-floating #biomass. The microorganisms combine to form #sludge flakes, which - depending on the #aeration process - can have different sizes. In contrast to biofilms, the expert can assess the condition of the system with the naked eye based on the color, shape, smell, quantity and settling behavior of the sludge flakes. The required aeration is generated with an air compressor and fed into the bioreactor via perforated #membrane aerators. Other aeration options are provided by #submersible aerators, #injector aerators and #surface aerators. Usually two pumps are required for the sludge transport. With this type of #wastewater treatment, the effluent classes C (carbon degradation) and N (#nitrification) can be achieved.

Special system features
Due to their biomass structure, activated sludge treatment plants have a good utilization of the reactor volume in relation to biofilm plants. The strength of the aeration must be designed in such a way that both the oxygen requirements of the microorganisms are covered and permanent #sludge deposits are prevented. In contrast to biofilm systems, the multiplication rate of the microorganisms is much higher, so that the biomass can adapt more quickly to different levels of pollution. Activated sludge treatment plants are not so sensitive in terms of #sludge removal from the primary treatment. For this reason, more sludge can be stored in the primary treatment than in biofilm systems. The waste water is fed into the bioreactor via a preliminary treatment (#settlement pit) in a free gradient and treated there. The cleaned water with the activated sludge flakes flows into a funnel-shaped secondary clarifier. So that the activated sludge can be supplied with oxygen again, a pump at the bottom of the secondary clarifier pumps part of the tank contents back into the bioreactor. The excess cleaned water flows through the secondary clarifier into the system outlet. Similar to biofilm systems, sludge is created by excess and dead biomass. This excess sludge is regularly conveyed to the primary treatment.

What should be given special attention?
Since activated sludge treatment plants work according to the continuous flow principle, activated sludge can be expelled if large amounts of water flow in for a short time. This biomass would then be lost for waste water treatment. This can be critical, especially for small plants that are intended for the #wastewater treatment of up to 20 residents.

What are the controls look like?
At least once a month it should be checked whether there is enough activated sludge in the system. Large amounts of floating sludge can form in the secondary clarifier, which must be skimmed off if necessary. The statutory controls must be carried out.

The fifth and last part of our series deals with the processes and systems that can definitely be described as "state of the art" in times of climate change and the associated water and climate protection and in terms of economy, performance, efficiency and ease of maintenance for are prepared for the future. So keep following us - now it's getting really exciting again!