Engineers at Servicios de Agua y Drenaje de Monterrey (SADM) in Monterrey, Mexico were presented with a challenge as they worked to provide potable water for the more than 3 million residents of the Monterrey metropolitan area. The area of Monterrey is located in a mountainous region of Mexico and a significant amount of the water comes from a natural park named La Huasteca.
A total of 20 wells are located in this area and supply up to 40 thousand gallons of water per minute to the surrounding region. Whenever problems arose in the wells, it required sending someone out into the rocky terrain to investigate each of the well pumping stations in order to determine where and what the problem was and then make the necessary repairs.
Like many municipal water systems around the globe, SADM began improving their water systems by adding PLCs to collect information from flow meters, energy meters and emergency plant controllers. This helped to more quickly diagnose problems at each pumping station, but they were limited on how that data could be relayed back to the central office because of the remote locations of the wells in non-populated areas.
Now, by using MaxStream's 9XTend wireless modems, SADM is able to remotely connect to each pumping station to monitor meter readings and equipment status. This real-time monitoring solution dramatically cuts back on maintenance costs because of the direct link that they have to stations spread across a large area. Ranges of several miles between data points are easily established by means of the one watt of output power, repeater capabilities and the outstanding receiver sensitivity. This wireless communication network (figure 1) is also used to automate chlorine injection as a function of total flow.

Figure 1. Wireless monitoring system architecture.

Data from a totaliser flowmeter is sent to the chlorine tank station, where a PLC receives this information, and adjusts chlorine supply according to flow variations as depicted in figure 2. System operators can also remotely close tank security valves, avoiding exposure to chlorine when leakage is present.

Figure 2. Chlorine supply automation system.

SADM is currently working to add more remote monitoring and control of their infrastructure by means of the 9XTend, including critical safety measurements at a nearby dam.
All information related to well operation is also sent using XTend radio modems to the nearest SADM administrative office. Information is received by a PLC and made available to all engineers in real time via an intranet site using a datalogger with compact flash memory and webserver capabilities. Historical information is used to detect and implement energy management strategies that result in lower energy costs.
ACEE Consultores (http://www.acee.com.mx), with the valuable help of MaxStream tech support, was in charge of the design and implementation of this radio modem based monitoring and control system. This project was developed in several stages and was completed in eight months.