Water Treatment Efficient Water Treatment and Distribution

Author / Editor: PRADEEP KARNIK / Dominik Stephan

The ever increasing cost of electricity and scarcity of water in most countries are forcing the utility operators to optimise their plants with the aid of modern technology. Industrial electronic devices, intended for control and monitoring – such as starters and electronic variable speed drives, can lead to 25 to 30 percent of energy saving in terms of electricity consumption. High time to take plant sophistication to water treatment and management systems...

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FIG. 2: Liquid cooled drives for efficient heat abstraction of electrical rooms
FIG. 2: Liquid cooled drives for efficient heat abstraction of electrical rooms
(Picture: Schneider Electric Industries)

Reducing the cost of electrical energy has become an imperative for managers and operators of water distribution systems and treatment stations. Industrial electronic devices, the use of which is growing in this sector, offer a practical solution to these requirements, and one that has already been proven in numerous installations. In India, with the introduction of PAT (Perform, Achieve, Trade) scheme, energy management in distribution and treatment of water is now a key buzzword.

Electricity, Treatment Agents and Delivering – Key Assets of Water Management

It has been found that water management involves the control of three key balance sheet items – which, according to the country, are divided more or less equally. These items are: electricity consumption (Fig. 1), purchase of treatment products (production and sewerage) and the personnel delivering the services. And electricity consumption often accounts for 30 per cent of the total cost.

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Reducing this item has therefore become an imperative for operators and managers of water distribution systems. Within this context, industrial electronic devices are increasingly being used in this sector:

  • to adjust the power factor to avoid penalties from the electrical utility and to reduce initial investment (size of equipment)
  • for management purposes, to reduce billing costs
  • to control motors (on pumps, agitators etc.) as a means of reducing consumption and extending the service life of equipment
  • to replace traditional control methods like motor-driven valves that lead to unnecessary energy consumption by pump motors.

In each of these cases, the savings, depending on the load level and the size of the installation, can be substantial. Motor control offers particularly great potential – as it allows a direct reduction in consumption (or in the number of kVAh to be paid for). In a pumping station, for example, the requirement is to start up the motor in the evening at full load and to stop it at dawn, for this purpose a simple starter is sufficient.

In another scenario, managing the variable flow rates will require a variable speed drive in order to achieve an animated effect. In the same way, to obtain a constant water pressure in the showers on every floor of a hotel simultaneously, regardless of the flow rate, the pressure will be regulated by means of a variable speed drive.

A typical problem encountered in a water board in the South, where the power supply was erratic, frequent tripping and failures of motors, operating on gen-sets necessitated reduced starting currents, hammering and low power factor.

Energy Efficiency and Reliability With Uneven Power Supply

The Variable Speed Drive (VSD) provides an answer to all these mentioned issues apart from saving energy as well. The ‘speed’ reference comes from a process regulator (flow or pressure) ensuring an optimal operation apart from protecting motor from all power issues, and enhancing availability. Today, almost all the motors in that water board have VSDs as a standard.

Variable Speed Drive (VSD) for Waste Water Treatment

The introduction of VSD in a sewage plant to drive asynchronous motor, replacing other mechanical solutions based on control valves, recorded significant energy savings and operating costs. Its main advantages include the suppression of pressure shocks (water hammer) during starting and stopping.

It forms the ideal partner to the ‘water hammer arresters’ fitted in distribution systems – thereby extends the service life of hydraulic equipment, and hence reduces overall costs. A further advantage is the reduction in the starting current, which in the case of large equipment helps in cutting installation costs...

Liquid Cooled Drive Increase Drive Efficiency

Liquid Cooled Drives (Fig. 2) are becoming a more attractive option for high Ingress Protection (IP54 and above), and increase drive system efficiencies. Internal coolant in the liquid cooled drives, collects the heat inside the power modules – where the heat is being generated, and dissipate it outside the room by exchanging with either water or air outside. Less than 0.15 per cent of total heat generated will be exposed to surrounding air, which is practically negligible. Therefore, no need of additional air conditioning.

Controls and SCADA – Managing Water Treatment and Distribution

As the technology improved so did the control processes. An example of this is the use of streaming current meters as a secondary control loop behind the primary flow pacing for coagulant dosing. The true power of the control system was the ability to combine large quantities of digital and analog data – and produce algorithms of greater complexity than can typically be achieved through combinations of single instruments.

Water operators have to manage infrastructure made of a lot of distributed and geographically dispersed sites. To achieve efficient operation, and to allow asset performance management, data consolidation is the key. Not only in terms of process, but also energy, and finally hooking to the enterprise level systems.

Efficiency 24/7 – Water Treatment Has Special Requirements

Water and wastewater infrastructures have to run 24 hours a day, 7 days a week. At the same time, infrastructure operation is conducted by a limited number of people, who should work in safe conditions. This calls for integrating process, power and video within a single environment, through consistent look and feel interface, which greatly improves SCADA operator efficiency and staff security, and enables the operator to visualise the problem through video – and react to security alerts immediately...

To get clear view about performance of assets, to decide improvement actions, and follow up results over time necessitate Energy Optimisation System (EOS) for water, at plant or remote control centre, wherein KPIs and trends combine process and energy data, bring real time visibility on plant energy performance and carbon emissions, and provide guidance for improvement through dashboards to allow benchmark of your assets.

Security too has become a major concern for water operators. Drinking water production and distribution, chemical storage at wastewater treatment plant require particular surveillance security operations on a single system, validation of entry into sensitive areas, information to audit log and greater traceability for events that occur.

Current Major Problems and Solutions for Water Treatment

The current main problem in water plants is correlating control and response. It is for the operator to respond to the plant and vice versa. Data is required to be churned out into useful information, which necessitates the understanding of the process constraints and the complex process interactions built on correlations between the variables, cause and effect.

There is a need for a process analyst tool that predicts the behaviour based on the available parameters by identifying patterns. This tool (Fig. 3) allows operators and process engineers to analyse the cause of process disturbances by bringing together trend and alarm data, which are traditionally stored separately. With the Process Analyst, users can simply view them all on a single integrated display.

Combining Flexibility and Efficiency

Complete flexibility is provided to the user on how the pens can be displayed, for example they can be overlaid or stacked and any pen can be placed in different panes to reduce clutter and make the display easier to read. The Process Analyst includes many unique features including true Daylight Savings Time support, accuracy to millisecond resolution, individual time axis per pen, customisable toolbars, rich printing and saving of all display settings for easy recall...

Root cause analysis: When a process upset or disturbance occurs, it is always time consuming to find the root cause. In the past, the process engineer had to compare trend data from the screen with alarm logs. With Process Analyst, all the engineer has to do is simply add any pen (analog, digital, alarm) that could have contributed to the process upset to the display. Each process change can then be easily compared as alarms occur, enabling sophisticated analysis of the process upset.

Compare different batches: With Process Analyst, it is easy to compare different batches in a single integrated view. Any differences in the batch execution will immediately be visible.

Sequence of events: With SCADA systems, the data is distributed around a wide area and typically the RTUs collect the data at millisecond resolution, and send it to SCADA every time it is polled. The Process Analyst displays historical alarms and trends to millisecond accuracy, making it easy to determine the sequence of events.

From Water Treatment to Water Distribution

Having achieved a level of sophistication at the treatment plants – it was natural to carry on and try to achieve the same level of control in the distribution system. The early development of telemetry was fraught with the problems of low data transmission speed, high latency, and the unreliability of radio or leased line communications used. The latest technologies including GSM, GPRS have simplified and stabilised the entire processes.

Need for Server Clusters

On the IT front, there is a need for Server Clusters capable of cross-supporting each other – such that one server may be the hot-standby server for many distributed local servers, or any combination of primary and hot-standby roles may be assigned to best suit the distributed network requirements.

Multiple ‘local’ servers collecting data and generating alarms and data logs for their local process area, with a single standby server at a central location that provides hot-standby services to all local servers. To prevent single-site reliance, that second local server shall have the next nearest local server as its hot-standby, but not the original server. This provides a ‘domino’ redundancy configuration that distributes the processing to reduce overall consequences due to a dual point-of-failure.

Tomorrow’s architectures (Fig. 4) are not limited to just servers to house the SCADA softwares but to include scalability, integratability to other systems including fire alarm systems, building management systems, access and security, electrical management systems, air conditioning, power quality and management systems, biometrics, CCTVs, hydraulic modeling, leak detection, LIMS, GIS and simulation software, integrated to provide a common look and feel.

Quo Vadis, Water Management? SCADA in Future

In the near future, SCADA would need to support a wide range of productivity analysis tools including: Key Performance Summary Indicators such as OEE, Availability, Reliability, Utilisation, Production against targets, Downtime accounting with clear client visualisation tools to identify productivity bottlenecks.

Also in the list, there will be: identification of poorly performing production areas and equipment, common failure causes, production accounting, with clear client visualisation tools to identify performance against budget, performance by shift, by crew, by product, by recipe, quality accounting, with clear client visualisation tools to identify non-compliant measurements, quality trends, quality by shift, by crew, by product, by recipe, tracking and tracing, with clear client visualisation tools to trace supplier materials throughout their distribution in the production system, right through to customer receipt, cost accounting, with clear client visualisation tools to identify the production costs associated with individual production areas, crews, shifts, products, recipes, and finally maintenance interface, with strong interfacing abilities to commercial maintenance packages.

Optimisation, Modelling and Simulation Packages

On the heavily cost-constrained water market, water utilities need to cut their operating costs while rising to the challenges of water quality, sustainable development, and ever more stringent regulations. Energy Optimisation System helps them do just that by optimising their energy use, which can account for up to 30 per cent of operating costs. It supplies plant operators and managers with real-time actionable intelligence that enable them to monitor, measure and manage how and where their wastewater treatment processes use energy.

Its user-friendly dynamic dashboard displays show at a glance, plant-wide pictures of energy consumption that use meaningful, customisable KPIs. They can drill down to individual energy- intensive processes and loads like aeration tanks to identify energy optimisation opportunities and take action.

How Energy Optimisation Systems for Wastewater Treatment Works

Energy Optimisation System for wastewater treatment plants (Fig. 5) encompasses functions that range from energy consumption and emissions monitoring and reporting to performance benchmarking and configurable alarms, and advanced power quality analysis and data securing. Benefits include lower energy costs per m3 of wastewater treated, higher energy efficiency, better quality electricity, better electricity supply contracts, and improved emissions performances.

On the distribution front, without real-time intelligence about operational performance, network status and customer demand, water utilities face the challenge of reacting swiftly to any change in these conditions apart from experiencing the challenge of deteriorating water quality due to aging distribution piping and depleting water sources.

Many have invested significantly in SCADA systems, which allow for partial monitoring of the network, but don’t offer the option of proactively simulating impacts on the distribution network. Most H2O utilities have only 20 per cent of their investment placed in the actual plant. The remaining 80 per cent is placed in the distribution network. And most have little or no idea of what happens to the water once it leaves the waterworks.

Regulatory standards are becoming more and more challenging to live up to, and require extensive documentation . even contingency plans for the unexpected. Another major challenge is Non-Revenue Water (NRW), which has a negative financial impact on water utilities, water resources and subsequently on the quality of the water itself.

Hydraulic Modelling Tool: How It's Used

Hydraulic modelling tool (Fig. 6) simulates the flow and pressure in the distribution network. Using real-time data to analyse and track the current situation, it enables operators to make better and smarter decisions, to optimise production and raise bottom line. Integrated with these modeling tools, there are a number of features and modules that enable you to achieve further savings on both operating costs and capital investments including:

  • Leak detection: To quickly detect new leaks in distribution network, with the most robust and reliable detection methods like Integrated Flow Measurement (IFM) and Night Line Measurement (NLM). You can also identify zones with leaks and signal alarm to the SCADA system to necessitate immediate action. 
  • Pump optimisation: To determine how the pumps in a distribution/ transmission network should operate at any given time in order to minimise the total pumping and energy costs for the network, while still supplying sufficient water to consumers. By combining pump efficiency, energy costs and water consumption, saving of up to 20 per cent of the pumping costs is possible.
  • Production optimisation: It integrates knowledge about the water producers within the network with hydraulic constraints and water supply, and identify the most economical way of operating the utility.
  • Pressure optimisation: To integrate the information from the SCADA system and the model to provide advice for optimal pressure operation of the network. Any reduction of pressure in the distribution network will have immediate and significant cost reductions.

Finally, water is the most critical resource issue of our lifetime, and our children's lifetime. The health of our waters is the principal measure of how we live on the land. Let us not wait for the wells to dry to know the worth of water.

* The author is the Vice President - Industry Business Unit, Schneider Electric, India.

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