How can sensors protect vulnerable areas? part 3

Today, advertisements for Camp Lejeune lawsuit settlements are frequently seen on cable and network TV. Another frequently cited water disaster occurred in Flint, Michigan.

Detecting lead in drinking water

On April 25, 2014, the City of Flint changed its water supply from Lake Huron (supplied by Detroit) to the Flint River. Subsequently, water distribution pipes corroded and leached lead and other contaminants into the city’s drinking water. In addition to physical health effects from lead exposure, 66% of the local households reported one or more adult members experiencing at least one behavioral health issue, and 54% of households reported that at least one child experienced at least one behavioral health issue.

One of the most common methods of measuring lead concentrations in water is inductively coupled plasma mass spectrometry (ICP/MS). It requires shipping water samples taken in the field to a laboratory, where a professional chemist performs ICP/MS testing. The highly accurate testing method uses an inductively coupled plasma to ionize the sample and create atomic and small polyatomic ions for detection.

In contrast, anodic stripping voltammetry (ASV), an electrochemical technique, can also detect the level of lead in water. The technique can be used in a portable testing system to avoid sending samples to a laboratory. In ASV, after reducing metals onto mercury electrodes by a current, a doped electrode used as a conductor determines the amount of metal plated on the electrode and, therefore, the concentration of metal in the water.

Lead service lines (LSLs) have been banned in the US since 1986. However, according to a report released in 2021 by the Natural Resources Defense Council (NRDC), a United States-based 501 non-profit international environmental advocacy group, between 9.7 million to 12.8 million lead pipes still carry water to homes in the US. The report also noted that 40 states did not know where their lead pipes were located. Adequate field sensing could identify these areas and avoid the problems experienced in Flint, MI.

Detecting intentional water contamination

In 2021, a water treatment plant in Oldsmar, Fla, was hacked. With remote control of a plant operator’s machine, the hacker increased the sodium hydroxide (NaOH) level in the city’s drinking water by a factor of 100, from about 100 parts per million to 11,100 parts per million. While sodium hydroxide, or lye, is the main ingredient in liquid drain cleaners, it also controls water acidity and removes metals from drinking water. The increased amount of NaOH represented a potentially dangerous increase. In this case, the hack was detected when a cursor, moving on its own, slid across a computer screen in the control room. Plant operators handled the increase in NaOH in the water, and local authorities enlisted additional help from the FBI and Secret Service to address the hack.

Since the water treatment process involves injecting sodium hydroxide into the water, reliable non-contact level measurements of NaOH with a local display and alarms are required to monitor the level in the storage tank. A reflective ultrasonic level sensor can be part of this aspect. Other sensors and controls in the water treatment plant monitoring system would have alerted the plant’s staff to the condition using process instrumentation that continuously monitors water quality parameters, such as pH, to ensure safe drinking water.