FEATURED ARTICLES Water Environment Solutions that Facilitate Ongoing Use of Water Resources

Techniques for Dealing with Risk in Systems

As an important part of the urban infrastructure concerned with water in cities, sew- erage systems are tasked with preventing flooding, improving public sanitation, and protecting the water quality of public waterways. In addition to these roles, the systems have also been subject in recent years to rising expectations for energy eff iciency and eff icient operational management. Hitachi is actively working to develop technologies and supply solutions that meet these needs. Among recent such activities is the develop- ment of operational support and control technology for preventing urban flooding and discharges of untreated , the aim being to reduce the risks of flooding and water pollution during rainfall events. In this way, Hitachi is seeking to contribute to the sew- erage industry as it takes on an even greater importance both in Japan and elsewhere.

Yoshinori Nishida Ichiro Embutsu, Ph.D. Hideyuki Tadokoro, P.E. Jp Masayoshi Hatayama, Ph.D. and P.E. Jp

solutions with a view to overseas applications as well as domestic users. 1. Introduction Th is article focuses on what Hitachi is doing in the fi eld of operational support and control technologies Internationally, Japan is one of the countries that that can help reduce the risks that stormwater poses has achieved a high level of success in dealing with to sewers in particular. sewerage, including by maintaining high standards of treated water quality and reliability of operation. 2. Hitachi’s Sewerage Monitoring Moreover, utilities and relevant government agen- and Control Solutions cies are seeking to maintain standards by pursuing future-oriented measures that address changes in both 2. 1 the business and natural environments, including the Overview of Past Developments increasing need for equipment upgrades, rising pub- Th e sewerage industry is one in which Hitachi has lic expectations, fewer young engineers entering the long been working on technology development. In profession, and climate change in the form of more order to supply a wide range of solutions encompass- frequent heavy rainstorms. ing all four areas listed in Figure 1, namely treatment In response to these trends, Hitachi is putting processes, monitoring and control, maintenance and considerable eff ort into developing technology and inspection, and recycling, Hitachi has developed pro- systems that are tailored to the latest needs of the cess monitoring and control technologies and simula- water sector, including sewerage, and is delivering tion techniques for the evaluation and prediction of

Hitachi Review Vol. 68, No. 5 648–649 81. Figure 1 — Hitachi Solutions for Sewerage Hitachi supplies a wide range of solutions that create value and reduce the load imposed on the environment by sewerage. Note that the figure includes solutions that are current under development or testing.

• Advanced nitrogen treatment • Energy-efficient control for • Fiber-optic systems for sewerage • Wastewater reclamation using microbial immobilization advanced treatment • Sewer inspection techniques systems technology • control for when [imaging, drones, fiber-optic • Production of methane gas from • High-speed nitrogen removal it rains sensors (multi-sensing box)] sewage sludge system (Anammox*) • Simulation of advanced sewage • Asset anomaly detection, etc. • Recovery of phosphorus from • Membrane bioreactor system, etc. treatment sewage, etc. • Sewerage energy management, etc.

Treatment Maintain and Monitoring Maintenance improve water Reliability and Resiliency and Recycling Value creation processes quality and control energy efficiency and inspection life extension

* Anammox is a registered trademark of Paques I.P. B.V.

the processes involved, making use of these in prod- improving practices at the pumping stations, sewage ucts both directly and indirectly. Th is has included treatment plants, and other infrastructure used to deal the recent development of a technique used in the with sewage will also increasingly be adopted given ammonia removal process of that that such methods are more economical. Hitachi is controls blower fl ow rates so as to reliably achieve working on digital solutions for addressing stormwa- the target water quality while also reducing power ter risks that also make use of technologies developed consumption and maintenance workloads. Th is in the past. Th e following sections describe the prog- technique was trialed as part of the Breakthrough ress of this work. by Dynamic Approach in Sewage High Technology Project (B-DASH Project) run by the Ministry of 3. Sewage Pumping Station Solution Land, Infrastructure and Transport from FY2014 that Mitigates Stormwater Risk to FY2015, with the ministry’s National Institute for Land and Infrastructure Management having Th is section describes a sewage pumping station published draft guidelines on how to introduce this solution that addresses the risks of fl oods, inunda- technology(1). tion of equipment, and water pollution within the service area. 2. 2 New Initiative for Dealing with Stormwater Risks 3. 1 One new initiative involves developing ways of Dynamic Pumping Station Simulator dealing with rainfall, something that is expected to As sewage pumping stations that form part of com- become more essential than ever as a consequence of bined sewers (sewers that handle rainwater runoff as climate change eff ects such as heavy rainfall events. well as other forms of wastewater) need to deal with a Along with fl ooding risks such as inland fl ooding or number of diff erent risks due to infl ows being higher the inundation of sewage treatment infrastructure, when it rains, keeping track of these everchanging another concern associated with rain is the risk of infl ows is an integral part of their operation. While city waterways being polluted by their primary priority is to prevent surface fl ooding overfl ows (CSOs) or the discharge of partially treated by quickly draining away the storm rain that falls in effl uent from sewage treatment plants. Measures for their sewage service area, their operation also needs addressing these stormwater risks in the past have to take account of risks that vary with the amount mainly involved physical infrastructure, such as of rainfall. Th ese include the inundation of sewage installing reservoirs or means of redirecting fl ows(2). pumping stations and environmental pollution caused It is also anticipated that operational measures such as by discharges of untreated effl uent.

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Hitachi has developed a dynamic simulator for to operate the pumps under the everchanging condi- sewage pumping stations that enables these stations tions (pump start/stop timings, changes to discharge to operate in ways that take account of these risks(3). levels, and so on). Th e planning and training exercise Th e simulator is made up of a set of separate mod- guidance function is also based on the dynamic simu- els that replicate in detail the specifi cations of the lator, using it to determine the operational outcomes pumping stations and their equipment. Taking the of adopting diff erent control techniques. To do so, it predicted infl ows to the pumping stations as its input, makes use of past data such as records of stormwater the simulator quantitatively assesses the risks (fl ood- and of actual pumping station operation. ing within sewage service area, inundation of pumping Figure 2 shows an overview of the operational guid- stations, higher discharges of pollution, higher energy ance function. Th e intended inputs include predicted consumption, and so on) associated with controlling and actual rainfall from the XRAIN* rain radar data the pumps using the diff erent techniques available as well as actual data on rainfall and trunk sewer water (feedforward control based on infl ows, control of levels transmitted over the sewer’s fi ber-optic network. fl ows into intercepting sewers, and the coordination Th e dynamic pumping station simulator is run using of control with the volume of wastewater receiving these inputs and guidance software used to generate high-level treatment). Th is provides valuable support operational advice. Th e plan for the future is to inte- for determining pump start/stop timings and dis- grate the function with external software for sewer charge levels during rainfall events when on-the-spot infl ow prediction or fl ood simulation. decisions must be made. Figure 3 shows an overview of the planning and training exercise guidance function. Th e inputs include 3. 2 the assumed rainfall pattern and the pump operating Guidance System for Sewage Pumping Stations conditions under the diff erent control modes (pump A guidance system currently under development uses start/stop timings, discharge levels, and so on). Th e the dynamic simulator described above to provide dynamic pumping station simulator is run offl ine a digital solution for sewage pumping stations. Th e using these inputs and the guidance software used to system has two functions: (1) Operational guidance generate advice for planning or training. Preemptively and (2) Planning and training exercise guidance. Th e simulating possible rainfall patterns and operating operational guidance function uses online data such as conditions provides a way to build up a library of infl ows and drain water levels that is transmitted over * XRAIN is a registered trademark of the National Institute for Land and Infrastructure the sewer’s fi ber-optic network to advise on how best Management, Ministry of Land, Infrastructure and Transport in Japan.

Figure 2 — Overview of Operational Guidance Function Information on rainfall data, trunk sewer water levels, and so on are input to the dynamic pumping station simulator and guidance soft ware is used to generate operational advice.

Provide guidance on what to do when it rains Operation

Dynamic pumping station Provide guidance for XRAIN actual and simulator predicted rainfall the different control practices out (pump on/off timings) Actual data from fiber-optic network (rainfall and water levels) Display risk assessment (risk visualization)

Identification of rainfall Software for predicting software Guidance patterns and selection in inflows, etc. Operate pumps based on of control mode guidance

Hitachi Review Vol. 68, No. 5 650–651 83. Figure 3 — Overview of Planning and Training Exercise Guidance Function A library of recommended operating practices can be built up by simulating diff erent rainfall patterns and pump operating conditions before they occur.

Preliminary study of operation and control practices Planning Dynamic pumping station Risk assessment for Data on past rainfall simulator different pump operation out events scenarios

Classification of rainfall patterns Build library of recommended pump operation scenarios for different rainfall patterns based Rainfall pattern to simulate on risk priorities in Guidance software Guidance Pump operating Software for predicting conditions under different inflows, etc. Utilize when operating pumps control modes during actual rainfall events

recommended pump operating practices under dif- use over the specifi ed time period and details of the ferent rainfall scenarios. Th is facilitates a prompt pump start/stop timings. Along with providing suitable response to actual events and the preemptive assess- advice on decisions about pumping station operation, ment of stormwater risks, providing key information it is hoped that the guidance function will also prove for decision-making such as the limits on what the useful for the transfer of operational expertise. infrastructure for dealing with stormwater can cope with and equipment upgrade plans. 4. Use of Wastewater Treatment Figure 4 shows one of the system’s pump opera- Control to Reduce Discharges During Rainfall Events tion guidance screens. Th e screen can be used to select which control mode to use for stormwater pumps while As instances may occur in which the higher infl ows viewing data such as rainfall amounts or current pump experienced by sewage treatment plants during parameters. Once other required control settings have rainfall events results in some of the effl uent being been entered, the screen can also be used to run the discharged without fi rst undergoing biological treat- dynamic simulator and display the results in the guid- ment. Th e challenges, then, include how to prevent ance area (central region of the screen). In this case, the unsanitary conditions and improve water quality in information clearly displayed on the screen includes the waterways into which the effl uent is discharged. recommended stormwater pump discharge rates to Measures for dealing with these challenges include

Figure 4 — Pump Operation Guidance Screen Along with displaying information on rainfall and plant operation, the screens provide useful sup- port for operational decision-making by showing the results of simulating diff erent control modes.

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Figure 5 — Overview of Operational Support and Control System for Sewage Treatment During Rain This uses a sludge settling model to assess the risk of sludge outflows from the final settling tank and utilizes this information for operational support and control. The aim is to reduce pollution discharges while also minimizing sludge outflow.

◆Sludge settling model ◆Risk assessment for ◆Operational support sludge outflow and control Replicates settling and movement • Alarms/operational guidance of sludge in final settling tank SS (mg/L) • Flow control (amount of secondary effluent) Sludge column Limit exceeded 40 (limit) Benefits of using flow control High risk 3.5 20 3.0 2.5 Medium risk Depth 2.0 10 1.5 Low risk Using standard operating conditions 1.0 5 Using flow control 0.5 Sludge depth limit Compare against limit Normal range Final settling tank for concentration of 0.0 Calculated sludge depth (m) sludge Calculated 0:00 12:000:00 12:00 0:00 suspended solids Time SS: suspended solids

reducing the amount of discharge by ensuring that as the end of the fi nal settling tank to use as an indicator much of the effl uent as possible is also treated in biore- of the risk of sludge outfl ow. Alarms and operational actor tanks (secondary effl uent)(4). As the fi nal settling guidance are updated based on this risk and it is also tank becomes a bottleneck when there is an increase in used in control of how much secondary effl uent there is. the amount of secondary effl uent, Hitachi is developing Control of how much secondary effl uent there is a technique for controlling wastewater treatment dur- works by calculating an upper limit for this amount ing rainfall events that helps maintain stable operation that ensures that the calculated sludge depth obtained by minimizing sludge outfl ow from this tank. by the sludge settling model does not exceed its own limit. Th is reduces discharges of pollution by maxi- 4. 1 mizing the amount of secondary effl uent while mini- Technique for Controlling Wastewater Treatment mizing sludge outfl ow from the fi nal settling tank. During Rainfall Events Th is technique uses a model of the sludge settling 4. 2 process in the fi nal settling tank to assess the risk of Study of Sludge Settling Model and Control Logic sludge outfl ow and modifi es how the operation is A desktop study of the sludge settling model and con- managed and controlled accordingly (see Figure 5). trol logic was undertaken using actual data from the Th e sludge settling model defi nes the mass of acti- operation of sewage treatment plants during rainfall vated sludge fl owing into the fi nal settling tank per events(5). unit time as one sludge column. Th e system simulates Figure 6 shows an example of plant data and sludge the movement and settling of sludge columns in the depth calculated by the sludge settling model for a fi nal settling tank and calculates the sludge depth at particular sewage treatment plant. Th e turbidity of

Figure 6 — Results of Sludge Settling Model The results indicate that the sludge depth calcu- lated by the sludge settling model can be used to 2.5 0 10.0 5.0 Rainfall Turbidity of secondary effluent 2 detect potential sludge outflows (increased turbid- 2.0 intensity 8.0 (measured) 4.0 ity of secondary eff luent)(5). Secondary 4 Calculated sludge depth 1.5 effluent 6.0 3.0 6

1.0 (NTU) 4.0 2.0 8

0.5 10 2.0 1.0 Relative water volume water Relative (planned volume = 1.0) Rainfall intensity (mm/h) intensity Rainfall Calculated sludge depth (m) sludge Calculated

0.0 12 effluent of secondary Turbidity 0.0 0.0 0:00 12:00 0:00 12:00 0:00 0:00 12:00 0:00 12:00 0:00 Time Time

Hitachi Review Vol. 68, No. 5 652–653 85. secondary effl uent increases as the volume of waste- References water rises, and this is accompanied by a rise in the 1) The National Institute for Land and Infrastructure Management (NILIM) of the Ministry of Land, Infrastructure, calculated sludge depth. Th is indicates that the sludge Transport and Tourism (MLIT), Technical Note of NILIM, settling model can be used to detect potential rises in No.938, http://www.nilim.go.jp/lab/bcg/siryou/tnn/ tnn0938.htm in Japanese. the turbidity of secondary effl uent. 2) MLIT, “Priority Measures of Sewerage and Wastewater Similarly, the results calculated with fl ow rate con- Management Department,” http://www.mlit.go.jp/crd/city/ trol enabled show that this reduces the risk of sludge sewerage/11pro/ in Japanese. 3) I. Embutsu et al., “Examination of Stormwater Risk outfl ow, with the sludge depth remaining below the Countermeasure Technology with Applied Pumping Station limit as indicated in Figure 5. Th e calculations also Dynamic Simulator,” Japan Sewage Works Association, Proceedings of 55th Japan Annual Technical Conference on demonstrated that changes to operational settings Sewerage, pp. 365–367 (Jul. 2018) in Japanese. such as the recirculation rate can amplify the benefi ts 4) T. Yamamoto et al., “Improvement of Combined Sewer in terms of reducing discharges. System Utilizing Existing Facilities in Osaka City: Development and Practical Application of Wet Weather In the future, Hitachi intends to establish control Activated Sludge Treatment Process,” Journal EICA, Vol. 10, techniques that will help maintain water quality, reduce No. 2, pp. 8–13 (2005) in Japanese. discharges, and improve the effi ciency of wastewater 5) Y. Nishida et al., “Development of Sewage Treatment Control Technology that Reduces Discharge Pollution Load in Rainy treatment during rainfall events by collecting data from Weather,” Japan Sewage Works Association, Proceedings operating plants and testing on pilot systems. of 56th Japan Annual Technical Conference on Sewerage, pp. 437–439 (Jul. 2019) in Japanese.

5. Conclusions Authors Yoshinori Nishida For all that the circumstances under which it operates Industrial System Control Research Department, Center for Technology Innovation – Controls, may continue to change with the times, the impor- Research & Development Group, Hitachi, Ltd. Current tance of sewerage infrastructure remains a constant. work and research: Research and development of monitoring, control, and information systems Hitachi continues to develop solutions that contribute for sewerage. Society memberships: The Society to the safety, reliability, and effi ciency of sewerage of Environmental Instrumentation, Control and Automation (EICA). systems while keeping pace with changes in the busi- ness and natural environments. Th e aim for the future, Ichiro Embutsu, Ph.D. Industrial System Control Research Department, meanwhile, is to further lift its involvement in the Center for Technology Innovation – Controls, Research & Development Group, Hitachi, Ltd. Current urban water cycle through its work on monitoring work and research: Research and development of and control technology and digital solutions by put- monitoring, control, and information systems for water supply, sewerage, and water environment. ting even more eff ort into technology development. Society memberships: EICA, the Institute of Electrical Engineers of Japan (IEEJ), and the Japan Society on Water Environment (JSWE). Acknowledgements Th e sewage pumping station solution described in Hideyuki Tadokoro, P.E. Jp Water Control Systems Engineering Department, this article formed part of independent research by Water, Metal and Industrial Control Systems Division, Control System Platform Division, Services the Hiroshima City B-DASH project and the con- & Platforms Business Unit, Hitachi, Ltd. Current trol technique for sewage treatment during rainy work and research: Development of monitoring and control system for water supply and sewerage. weather was part of joint research with the Laboratory Society memberships: IEEJ, EICA, and the Society of of Professor Hiroaki Tanaka, Graduate School of Instrument and Control Engineers (SICE).

Engineering, Kyoto University. Th e authors would like Masayoshi Hatayama, Ph.D. and P.E. Jp to express their deepest thanks to everyone involved. Technology Development Department, Water Solutions Division, Water Business Unit, Hitachi, Ltd. Current work and research: Planning of research and development for water supply and sewerage systems.

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