Water quality is a critical issue in Sri Lanka. Industrial pollution and contamination from dumping waste are the top contenders in a long list of factors impacting Sri Lanka’s poor water quality. It has gotten so out of hand that it was reported local restaurants were using water from illegal boreholes rather than use the town’s public supply. The effects of utilizing poor water have been reported in the form of skin diseases, hepatitis and other grave health issues.
In light of health risks, there has been a big push to quickly address the water supply issue. One system that has been deployed is already improving the water quality situation. It is a SCADA (Supervisory Control and Data Acquisition) managing hundreds of mobile reverse osmosis (RO) stations.
Reverse Osmosis Stations Restore Water Quality
Reverse Osmosis is used to remove the majority of contaminants from water by pushing it under pressure through a semi-permeable membrane. Typically, there is a wide array of dissolved minerals in groundwater. The naturally dissolved minerals, such as salt, as well as dissolved industrial contaminants are removed by the RO process, creating demineralized water that is safe to consume. RO stations are placed at various wells to supply clean drinking water for the local residents.
The testing of the RO process on water quality is typically done via electrical conductivity. Conductivity is determined by the quantity of ionized substances, such as acids, bases, and salts that are dissolved in water. Demineralized water is a poor electrical conductor.
The SCADA system for this water-monitoring project has been configured and the project is well underway. The SCADA is monitoring the state of the RO stations to assess if they are working properly. It checks the quality of the water and reports on such indicators as PH and conductivity values as well as monitoring the status of the stations pumps. Each RO station has about 10 tags that are being monitored for this purpose.
There are approximately 80 RO stations that have been installed at well sites. The RO stations use the SIMATIC S7-1200 PLCs (programmable logic controllers). The stations communicate with cellular modems that are connected with PcVue’s SCADA system via Siemens’ OPC TeleControl server.
There are alarms configured in the PcVue SCADA to alert adverse conditions at the station. These alarms are raised when there are any changes to station status. Alarms also drive animations in the graphical user interface; producing color changes, changing text strings and driving the appearance of graphical symbols, which makes it very easy to maintain the graphical display.
An operator who has credentials granting them appropriate user rights can acknowledge alarms. User rights provide a level of security for the actions within the PcVue SCADA application. In this distributed application, alarms or changes to any status points are acquired by the SCADA server in the control station. This ensures the control station is aware of acknowledged alarms and allows them to track the status of various wells.
The Use of Mobile Telecommunications
The PcVue SCADA application uses the built-in GEO Map control (graphical component) configured for a GIS (Geographical Information System) decision-making display within the SCADA graphics. The GEO Map control uses a standard map provider, in this case Google Maps, which is overlaid with markers created by the PcVue editor capable of displaying real-time information representing the RO stations. The SCADA GIS allows the operator to locate and track the RO stations with ease.
To acquire the status of each station, PcVue connects with TeleControl. TeleControl uses General Packet Radio Service (GPRS) and long-term evolution (LTE) for telecommunications. GPRS is a packet-centric mobile data service on the 2G and 3G cellular communications global system for mobile communications (GSM). LTE, a 4G technology, has become the accepted standard for wireless communication of high-speed data for mobile phones and data terminals. TeleControl is able to transmit data at speeds of up to 60 Kbits per second using an energy efficient method to send and receive data. It is a good choice for remote applications with proven reliability and battery efficiency, particularly when monitoring and supervising remote RO stations.
Tal Niv, CEO of Shaniv Control and Automation Ltd. is a PcVue certified partner integrator and engineering company for industrial control and automation projects and the one who configured the system. He designed the mimics (graphical user interface displays) within PcVue and configured them with icons so that operators can more readily monitor the remote RO stations. For example, there is an icon that changes color to illustrate to the operator whether the pump is functioning properly or not.
The SCADA software has been configured so that the operator can change the identification and the physical location of the RO stations without the need of a PcVue SCADA specialist. The operator is able to maintain the SCADA map displays by editing the identification or the latitude and longitude for any of the RO station marker. This helps in identifying quickly when the RO station has been moved and where they are all located at any time. The displays also provide the control station operator with a comprehensive overview of the system-wide operating status and a visualization of all RO station’s status and location.
This keeps everything manageable and allows the control station to efficiently track where the RO stations are installed and accurately track the water quality at any given well. PcVue SCADA combined with Siemens’ S7 and TeleControl is working in harmony and has proven to be a very effective, affordable, and flexible solution.