Myths about wastewater treatment automation: the screw press makes work easier but not entirely human-free

Automation is now a common requirement in most manufacturing and process technologies. The wastewater treatment sector is no exception. We are also moving towards automation: the screw press, our sludge dewatering machine, is designed for continuous operation. When running, it can be unattended the vast majority of the time. While automation reduces the need for human presence, it does not eliminate it. What are the possibilities of automation within the sludge dewatering process? Find out in this article.

Automation: screw press vs. the others

For sludge treatment purposes, several types of dewatering devices can be used in WWTPs. The most commonly used are screw presses, centrifuges, and chamber sludge presses/chamber filter presses. Of course, each has its advantages and disadvantages.

For example, as far as automation is concerned, the chamber press does not hold up. Why? Because dewatering is a discontinuous process in the case of this device, which cannot be done without the constant intervention of the operator. The sludge chamber is gradually filled with sludge until the chamber is full, then the contents are squeezed to remove excess water. And then comes the moment when human power kicks in. Operators must manually remove the squeezed sludge. Due to the work's enormous physical and time-consuming nature, a chamber press is an unsuitable device for larger sludge volumes.

Centrifuges can also have a problem with automation. Although dewatering is a continuous process with these high-speed devices, they are very susceptible to damage during initial start-up. The several-minute start-up process cannot be done without the operator's sharp eye, which no automation is yet able to replace.

As mentioned above, our screw press is a stand-alone device that is capable of continuous operation. Even in its case, however, automation has its limits.

Limits of automation

In practice, we see that many customers have false ideas about automation. They think that with a screw press they will be able to start the sludge dewatering process from the comfort of their office. But that's not how it works. We would describe our view of automation like this: Automation puts humans and technology in the role of partners. Automation technology helps people to keep technological processes efficient and safe. But one cannot do without the other.

The automation of the screw press is mainly based on the fact that the machine is largely self-monitored during operation. However, a human presence is always required at the beginning and end of the dewatering process. Particularly at the end, when the press requires a clean water rinse to prevent residual sludge from drying out and potentially damaging the machine at the start of the next cycle.

As far as polymer preparation is concerned, automation is also an option here: automatic polymer preparation stations can continuously mix liquid or powdered polymer concentrate with water without operator assistance. However, the automation of polymer preparation goes hand in hand with the continuous operation of the press itself. For example, it is unnecessary to have an automatic station for a dewatering plant that is only in operation for 6 hours a day and requires the presence of an operator who can manually mix the polymer at the start and end of its operation. When does the use of automatic polymer stations make sense? Mainly for large machines whose hourly material consumption is so high that it would be more or less impossible to do it manually, or for operations that are indeed continuous.

Rapid changes do not play into the hands of automation

Those who are in the industry know that the result of dewatering does not only depend on the dewatering equipment used but mainly on the qualities of the sludge. And these can change from minute to minute. It could be said that WWTPs, and therefore sludge, behave like living organisms. The properties of sludge change, for example, depending on the number of rainfalls or environmental accidents. Sludge will also change if a food processing plant is newly connected to the sewerage system, or at Christmas time when people cook and eat at home. Even something as seemingly small as a certain village being supplied with a new bakery with a specific sourdough recipe will have an impact on the sludge. All of these changes need to be responded to flexibly when dewatering the sludge, which is the strength of human operators.

Automation is a necessary part of the development of wastewater treatment, although it has its limits, at least for the time being. Our plants for efficient sludge dewatering fully meet the current requirements for automation.

Contact us. We can provide you with a meaningful dewatering solution.