To cater for ever-increasing water demand for proposed site and nearby factories, a plan have been set in place to build a UF and RO plant to cope with water demand in the surrounding glove factories.
Once water demands are met, excess water are being sold to neighbouring factories to generate income to maintain the plant.
First phase of the plant will be a 200m3/hr UF and a 120m3/hr RO, with plans for additional to be added as a new plant or expanded to the existing plant. The proposed plant will take raw water from the retention pond nearby and filter the water into a newly built UF tank and RO tank.
Requirements
- To design a fully automated plant with SCADA to capture plant entire operating data.
- The plant controls has to be automated and able to be monitored remotely as the plant is required to run 24 hours a day with no full-time operator on-site.
- Besides remote monitoring, remote control is also required to enable operators to rectify or manually override the system remotely in case of any fault within the plant, requiring human intervention.
- During system fault, there must be a fast method to alert the operators that are out of plant facility in order for the operators to act fast on faults occurred.
- Various water quality sensors need to be installed to facilitate the automation and system decision making process, eliminating the need for human to make critical decisions during operation.
- Output of the plant needed to be recorded in a reliable fashion as the treated water is sold to other plants and therefore full accountability needs to be in place.
- Plant running parameters are available at all times to monitor for any water input or output quality anomalies.
- Plant design must be modular to enable ease to add future sensors or to allow plant expansion into the existing design / system.
- SCADA is required to store data in reliable fashion as the water treated is to be sold, and should any arguments arises due to unsatisfactory water from the plant, the data is readily available for counter-argument or post-mortem purposes.
Solution
- The plant is configured in 3 x 80m3/hr MF+UF and also 5 x 40 m3/hr RO to meet the specifications required with some spare capacity for backwash, CEB and CIP downtime.
- A PLC and 10” touchscreen is installed to serve as the autonomous control system with the 10” touchscreen serving as the Human-Machine interface.
- On top of that, a dedicated SCADA system is deployed to record operating data from the PLC for further analysis. Data is stored using SQL database system due to the huge amount of data collected from the plant.
- Proper report charts are programmed into the SCADA to allow daily report to be generated and sent to the respective person-in-charge email addresses.
- To fulfil the monitoring and control needs of the plant, the following instruments are installed:
- UF Inlet flow meter
- RO Inlet flow meter
- RO Outlet flow meter
- UF to TWT tank flow meter
- UF tank ultrasonic level sensor
- RO tank ultrasonic level sensor
- UF outlet turbidity sensor
- RO inlet and reject turbidity sensor
- RO inlet, outlet and reject conductivity sensor
- RO inlet ORP sensor
- RO outlet and reject pH sensor
- UF to TWT tank turbidity sensor
- Incoming pond turbidity sensor
- TWT header to UF tank turbidity sensor
- Rain gauge
- All water quality related instruments are installed in a sampling pipe to allow easy access of all sensors in one place
- REMOX system which includes 4G connectivity is installed to allow the plant to be monitored and controlled from outside plant facility.
- Password access is enforced to allow only authorized personnel to login and monitor the plant.
- To facilitate the maintenance, the system also allows re-programming remotely without having to be on-site. Remote maintenance is a must for such system to allow short turn-around time during plant fault as the plant is contracted to supply water to neighbouring plants, and any down-time usually means a penalty can be imposed due to breach of contract requirements.
- To ensure operators or management get the best heads-up during plant fault, a email alarm messaging system is provided from the SCADA system. All critical alarms occurred at plant will be relayed to the operator or management at real-time through email service with a proper timestamp.
- On the mechanical side, due to the pumps are installed with softstarter to eliminate water hammering from happening during pump start/stop cycle. This is crucial as UF and RO system have heavy start/stop cycle to change between filtration, backwash and CEB modes.
Conclusions
- The system delivered is able to run in fully automatic mode, lessening the amount of manpower needed.
- The enhancement of REMOX remote monitor and control function drastically helped the team to troubleshoot and resolve any issue easily without being physically on-site.
- Daily report email on plant last 24hour operation helped the operators and management to determine the operation efficiency of the plant easily make decision on how to tweak the plant to achieve higher efficiency. Power-per-m3 of treated water is able to be calculated as the system also takes the current and voltage reading from the power meter of the control panel.
- Due to SCADA system constantly taking record of the sensors and auto-generate the report, the operators are relieved from the job of manually taking the sensor data and preparing a daily operation report for the management.
- Any fault in the system can be easily identified using the SCADA system as all sensor record are in one single place with proper timestamps.
- Areas to be improved:
- Email alert system can be enhanced with a SMS alert system which is able to alert the operators faster than email (SMS alert is omitted from earlier design due to cost to maintain an unlimited SMS line)
- Softstarter sizes need to be upsized in the future as the start/stop cycles have exceeded the allowable limit of the device. Program logic need to be enhanced to take into account of start/stop cycle an hour to ensure the limit is not breached during normal operation.
- Dedicated sampling pump to be installed for the inlet pond water turbidity sensor as currently it is relying on the pump operation to draw water to the sampling pot.
