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Sludge Management and Wastewater

The optimal pH for the function of activated sludge is 7, i.e., neutral. However, the biocenosis of the activated sludge can adapt within a pH range of about 6-8, provided that it is stable and does not fluctuate. In the case of fluctuations, it will be a problem to keep the biology at the WWTP in a functional state. It is then necessary to deal with the neutralisation of the wastewater before its actual treatment at the WWTP.
If proper maintenance is not performed on the wastewater treatment plant, the first issue to occur will be over-sludging. This manifests as an increase in the concentration of activated sludge in the activation process beyond the optimum (3-4 kg/m3, which corresponds to about 30% of the volume of the sample taken after settling for 30 minutes). As a result, activated sludge will eventually start to escape into the outflow, typically occurring when the sludge concentration exceeds about 60-70%.
Samples are usually taken only at the outflow. In this case, the sampling point is from the outlet pipe to the emergency overflow, the last accessible point before the discharge from the plant. In the case of additional installed cleaning stages, it logically is always the last accessible point before leaving the plant. If it's necessary to also take inflow samples it's most appropriate to place a container under the inflow pipe so that all incoming wastewater passes through this container and then take a 'mixed' sample from this container. As an optional accessory, the plant can also be supplied with an additional sampling container installed inside the plant, where the necessary amount of water for sample collection is always available.
A properly functioning wastewater treatment plant does not emit odors. If there is an odor, it indicates anaerobic conditions in some part of the plant which should not normally occur as all compartments of the plant should be sufficiently aerated. In such a case, it's necessary to identify the malfunction or the cause of the oxygen deficiency in the specific smelly compartment. Therefore, the plant should never smell like a septic tank or cesspit. However, it's important to remember that the wastewater treatment plant accumulates wastewater which can have an inherent odor.
A wastewater treatment plant is much less infectious than a septic tank. This is due to, firstly, the principle of smaller volumes of wastewater and smaller dimensions of the facility itself, and mainly due to the different processes occurring in both systems. In a septic tank, anaerobic processes take place, resulting in biomass, water and biogas composed mainly of methane and hydrogen sulfide, which are toxic gases and hydrogen sulfide also has a strong odor. Additionally, anaerobic processes minimally remove pathogenic microorganisms that can cause infectious diseases. In contrast, in an aerobic wastewater treatment plant, oxidation of water and all substances contained in it leads to their purification and simultaneous disinfection. It has been proven that 99% of all pathogenic microorganisms in raw wastewater are eliminated during the aerobic cleaning process in wastewater treatment plants due to oxidation. The final products of aerobic wastewater treatment, in addition to biomass are water and carbon dioxide, which are harmless and odorless gases. Furthermore, the system can be equipped with chlorine disinfection or a UV lamp for additional disinfection of the treated wastewater.