Using CompactRIO and NI Developer Suite to Automate a Manganese Removal System in a Water Treatment Plant

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"With a fully automated system developed using National Instruments hardware and software, we increased the productivity and reliability of the plant. "

- Thomas Ari Negara, CV.BERKAT ANUGERAH

The Challenge:
Increasing tap water quality to meet standards from the Ministry of Health of the Republic of Indonesia by developing a manganese removal system for a water treatment plant that processes water at a rate of 8,640 m3/h.

The Solution:
Using the NI Developer Suite and NI CompactRIO hardware to develop a full supervisory control and data acquisition (SCADA) system that has the following features—static and dynamic animation, an alarm log, real-time and historical data trending, a tabular database, setting parameters, and user-level security.

Author(s):
Thomas Ari Negara - CV.BERKAT ANUGERAH

Manganese is a mineral that is naturally found in rocks and soil. It is a normal constituent of the human diet. It exists in well water as a naturally occurring groundwater mineral, but may also be present due to underground pollution caused by industrial activity.

In a set of 237 raw water samples from Jakarta, Bogor, Tangerang, and Bekasi examined by the Puslitbang Farmasi Ministry of Health in the Republic of Indonesia, 89 samples (35.9 percent) were found not suitable for drinking and 50 samples (21.1 percent) exceeded the maximum allowed amount of manganese concentration as determined by the Ministry of Health of the Republic of Indonesia. The average manganese concentration found was 0.91 milligrams per liter of water (mg/L). The maximum allowed manganese concentration in tap water is 0.4 mg/L, and manganese may become noticeable in tap water at concentrations greater than 0.05 mg/L by imparting a color, odor, or taste to the water.

Exposure to high concentrations of manganese over the course of years has been associated with toxicity to the nervous system, producing a syndrome that resembles Parkinsonism. This type of effect may be more likely to occur in the elderly. A modern water treatment plant (WTP) should have a manganese removal system that ensures the manganese levels are low enough that there are no potential risks to the nervous system, even in those who may be more sensitive.

Methodology

In general, manganese oxidation is difficult because of its slower reaction rate. A longer detention time (10 to 30 minutes) following a chemical injection is needed prior to filtration to allow the reaction to take place. In this system, we use manganese greensand as the filtration medium. Manganese greensand is the most common medium for removing manganese through pressure filtration in fully automated systems. Greensand is a processed material consisting of nodular grains of the zeolite mineral glauconite. The material is coated with manganese oxide. The ion exchange properties of the glauconite facilitate the bonding of the coating.

The treatment gives the medium a catalytic effect in the chemical oxidation reduction reactions necessary for manganese removal. This coating is maintained through either a continuous or intermittent feed of chemical injection.

To optimize the control of the manganese removal system, we proposed developing an automation system using an NI cRIO-9073 real-time controller and a SCADA system based on LabVIEW. With the NI Developer Suite 2011, we developed a full SCADA system that has the following features: static and dynamic animation, alarm log, real-time and historical trend data, a tabular database, setting parameters, and user-level security. With a fully automated system developed using National Instruments hardware and software, we increased the productivity and reliability of the plant.

System Operation

Raw water temporarily enters tank LT-101. Raw water is transferred to the filter tanks V-100, V-200, V-300, and V-400 by feed pumps P-101, P-102, and P-103, to be processed with filtration and chemical injections. The speed of the feed pump is regulated by a proportional integral derivative (PID) controller to maintain the water level in tank LT-101. To make sure each feed pump runs for the same number of hours, we developed automatic switching based on a real-time clock on the cRIO-9073:
• 0 to 8: P-101 and P-102 running
• 8 to 16: P-102 and P-103 running
• 16 to 24: P-103 and P-101 running

There are two processes on the filter tank that run simultaneously—filtration and chemical injection. The filtration on each filter tank is monitored by the value of the differential pressure inlet and outlet. When the differential pressure exceeds the limit setting, the controller commands the filtration valves to close and the maximum speed on the feed pump is reduced. After that, the controller commands backwash pumps P-201 and P-202 to turn on alternately until the differential pressure in the filter tank is less than the limit setting. A chemical injection is conducted by controlling the pulse rate and length of the dosing pump where the flow rate of the chemical injection is determined by the flow rate of the raw water to the filter tank.

After the filtration and chemical injection occur on the filter tank to remove the manganese, the tap water transfers to tank LT-102 and it is ready for the residents of Pantai Indah Kapuk (PIK), Indonesia to consume.

To monitor the performance of the manganese removal system, we installed a water quality sensor to analyze the pH, oxidation reduction potential (ORP), conductivity, turbidity, chlorine, and manganese levels before and after the water passes through the filter tank. Because of the limited capability of the chemical injection to remove manganese from the raw water, we implemented a security feature to halt the system if it is damaged or exceeds capacity. The controller commands the manganese removal system to automatically stop and open valve XV-601 when the manganese content of the tap water is more than 0.4 mg/L.

Author Information:
Thomas Ari Negara
CV.BERKAT ANUGERAH
JL Pool PPD Pesing Poglar, Pergudangan Prime Centre 2 Block A/9
Indonesia
Tel: +66221-29030973
Fax: +6221-29030908
THOMAS.WHY05@GMAIL>COM

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