Business Strategy Division, R&D Center
Solution Technology Development Department
Control Technology Development Group
Daisuke Naka
Business Strategy Division, R&D Center
Water Regeneration Technology Development Department
Shotaro Hatsuyama
The “Demonstration Project for Advanced treatment technology involving controlling the single tank nitrification denitrification process with ICT and AI” was adopted as a 2019 theme of the MLIT’S “B-DASH” projects for promoting innovative technologies for sewerage.
To promote advanced treatment of sewage, the technology was aimed at improving treatment capacity, energy-saving, and reducing burdens in terms of maintenance and management. What makes the technology innovative? And what was the result of the demonstration study?
We conducted an interview with Shotaro Hatsuyama and Daisuke Naka, the project members who know the best about the field.
The B-DASH Project is short for “Demonstration Study of Breakthrough by Dynamic Approach in Sewage High Technology Project,” which is led by Ministry of Land, Infrastructure, Transport and Tourism. The project is aimed at improving efficiency of energy use and reducing life cycle costs in the sewerage business by accelerating R&D and the commercialization of innovative technologies, as well as by the supporting overseas water business conducted by Japanese companies.
“Demonstration Project for Advanced treatment technology involving controlling the single tank nitrification denitrification process using ICT and AI” was conducted by a joint research team consisting of Machida City, Japan Sewage Works Agency, and METAWATER. It was adopted as one of the B-DASH projects for FY2019. The demonstration study was conducted over the course of a 2-year time frame at the Naruse Clean Center in Machida City.
Hatsuyama Many wastewater treatment plants in Japan are now facing the problem of facility aging. Furthermore, as the need for facility consolidation and discontinuation increases due to decreasing populations, we are being asked how water treatment ought to be as we look toward the future.
Advanced treatment to conserve water quality is one of the solutions to address the problem, although it presents other challenges as well, such as construction and maintenance costs for facilities and their treatment capacities.
Amid such circumstances, we started exploring technologies to enhance treatment capacity using the existing civil engineering frameworks without introducing additional power equipment, while at the same time securing water quality that is equivalent to that offered by advanced treatment.
Hatsuyama This technology consists of three element technologies used to provide integrated control of reaction tank equipment and blower equipment (see above figure).
First, the “single tank nitrification denitrification process ("Element Technology 2" in the figure)” features a reaction tank used for the removal and reduction of organic substances, phosphorus, and nitrogen in wastewater with the aid of microbes. Our goal was to achieve treated water quality equal to that provided by the A20 method, with shorter detention time in the reaction tank; in other words, we wanted to improve treatment capacity. The key to this innovative technology was the control that enabled sending appropriate air volumes according to load fluctuations in the tank. This control allowed ideal zone forming in a single tank for the aerobic zone, where microbes that prefer oxygen work, and the denitrification zone, where microbes that perform nitrate respiration work.
Naka Water quality sensors are installed inside the tank. The NOx-N (nitrate-nitrogen and nitrite-nitrogen) sensor near the center and NH4-N (ammonium-nitrogen) sensor at the end, are particularly important. Continuously measured data are sent to the Integrated Computing System ("Element Technology 1" in the figure) and used for automatic calculation of required air volumes. According to the required air volume, a command for the optimum discharge pressure is sent to the “load fluctuation-tracking blower unit ("Element Technology 3" in the figure). This is how real-time automatic control is achieved.
Hatsuyama This technology demonstrates high treatment capacity without the mixers or circulation pumps required with the A20 method. It also does not require a wall to separate aerobic and denitrification zones. Also, a configuration using ICT and AI enables integrated control of reaction tank equipment and blower unit equipment, which used to be optimized independently. It allows us to achieve stable quality of treated water and minimum energy usage without the need for advanced operational management technologies.
Naka I felt it was wasteful to run the equipment at a full power when the air blower unit could be operated in energy saving mode. This system also employs automatic tuning of control parameters through machine learning conducted by AI to address seasonal variations. It can respond reliably to factors such as the activation of microbes that are affected by water temperatures.
[Water treatment facilities at the Naruse Clean Center]
The reaction tank is installed under the dome-shaped cover.
[Air diffusion units installed inside the existing reaction tank]
The flat blue devices send appropriate air volumes.
●Treated water quality
Sampled effluent water at the final sedimentation tank of the demonstration site facilities and measured organic substances, phosphorus, and nitrogen.
The average concentrations of each substance were below the targets.
A nitrogen removal rate equal to that provided by the A20 method (60-70%) was achieved.
●Treated water quality
Sampled treated water at the final sedimentation tank of the demonstration site facilities and measured organic substances, phosphorus, and nitrogen.
The average concentrations of each substance were below the targets.
A nitrogen removal rate equal to that provided by the A20 method (60-70%) was achieved.
●Treatment capacity
Measured the detention time of inflow sewage in the tank.
Although we have set the target at 12.8 hours or less, which is a 20% reduction from the general detention time of the A20 method (16 hours), the result was much shorter during the demonstration: about 10 hours.
●Electricity consumption of blowers
Achieved the reduction target of 10% or more.
●Water treatment electricity consumption
Achieved the reduction target of 20% or more compared to A20.
●Automatic control
For NOx-N and NH4-N, the match rates between control targets and measured values were analyzed.
Achieved a challenging target wherein 95% or more of measured values fall within ±0.5 mg/L of the target.
●Maintenance/management items
The number of maintenance/management items was reduced in comparison to A20.
●Construction cost
Cut by more than 20% compared with A20 (new construction).
●Maintenance/management cost
Reduced compared to A20.
Naka I was worried at first when this project commenced about whether we could launch the AI successfully. Because we cannot obtain demonstration data concerning water treatment if we cannot manage air volume control. It turned out, however, that we were able to finish the 2-year demonstration study without running into any significant trouble.
Now, although the technology is being studied as a part of voluntary research, I personally have a lot of things I want to explore more deeply.
We have not gone so far as to identify the limits of cost reduction in terms of middle and long-term perspectives and the detention time required in water treatment, so the chances are that we will be able to reduce them further. I also want to work on approaches to improve usability, for example, organizing the procedures to return from automatic control to manual operations, which is necessary when inspecting electric equipment.
This technology has received an endorsement from the government through the demonstration project, and I feel the immense potential of it and want to further enhance its added value.
Hatsuyama We had to make substantial achievements over the course of a two-year time frame within the B-DASH Project. This demonstration study used the first 9 months for facility renovation, leaving only one year and three months for the study. I sometimes felt impatient because we needed to obtain seasonal data, which depend largely on microbe activities, and thus required us to keep watching how things were going all the time. What helped us during this situation was a system which involved a combination of mechanical and electrical engineering, which is unique to METAWATER. If problems came up in terms of control, I spoke with Naka, who solved the problems promptly and gave me a sense of reassurance.
I experienced a lot of things during this demonstration study while also improving my skills. I’ll keep challenging myself from here on.
Business Strategy Division, R&D Center
Solution Technology Development Department
Conversant in sewage treatment plant controls, and kept an eye on the overall control of the reaction tank during this demonstration study.
Also engaged in developing tools used for operation, maintenance, and management, including the semi-automation of daily and monthly report creation.
Business Strategy Division, R&D Center
Water Regeneration Technology Development Department
Led this demonstration study at the forefront since the development of the single tank nitrification denitrification process. Naka calls him, the person closest to the customer.
Plant Engineering Division
Section Manger, Sewage Technology Department
Shigeru Machida
Plant Engineering Division
Section Manger, Sewage Technology Department
Kazuhiko Saeki
Business Strategy Division, R&D Center
Resource Recycling Technology Development Department
Naoto Watanabe