What are the Basic Water Quality Standards and the Importance of Water Quality Sensors?

Water is essential to power plants, fertilizer, pharmaceuticals, beverage, chemical processing, and wastewater treatment industries. A single industrial sector could have varying requirements for water quality standards. Water undergoes various chemical and physical treatments while passing through multiple sections within these industries. Monitoring these changes is essential to ensure compliance with all water quality standards. It necessitates the need for water quality sensors.

Water quality sensors can vary in detecting parameters, range, communication protocol, and construction. It is vital to ensure that the physical, chemical, and biological parameters are within the sensor's detection range. The parameter ranges are defined by the various regulatory or standard requirements. Maintaining maximum compatibility with your system leads to higher yields, efficient process, and rapid response to abnormalities.

Let's begin by understanding the basics of water quality standards, key parameters that water quality sensors detect and then discuss the importance of water quality sensors in various applications.

Basic Standards of Water Quality

Maintaining water quality is vital for drinking or industrial applications. Low pH, detected by water quality sensors, can damage carbon steel-based piping and be critical in some chemical processes with non-metallic piping. Similarly, water for human consumption may contain contaminants that are detectable through water quality sensors that provide turbidity, conductivity, and other process parameters. Let's dive deeper into water quality standards for a broader understanding of water quality.

♦ Definition of Water Quality Standard (WQS)

According to the United States Environmental Protection Agency (EPA), water quality requirements depend on three main factors: the water user, parameter requirements to protect the user of water, and antidegradation requirements to ensure sustainability. These three core components form water quality. Various organizations standardize the water quality by defining the control parameter ranges, which are monitored using water quality sensors.

♦ Regulatory Bodies

Multiple regulatory bodies define the requirements of WQS based on application. Here are the key organizations that standardize water quality:

• United States Environmental Protection Agency (EPA)
• American Society of Mechanical Engineers (ASME)
• Food and Drug Administration (FDA)
• American Society for Testing and Materials (ASTM)
• United States Pharmacopeia (USP)

While most regulatory bodies may define water quality for specific processes, the EPA provides comprehensive guidelines across all industrial sectors. It is divided into titles, parts, and sections for specific applications.

♦ Examples of WQS

1. General Industrial Water Quality Standards

Organizations such as the World Health Organization (WHO), International Organization for Standardization (ISO), and EPA provide generic guidelines for industrial water use. It should have:

• pH: 6.5 – 8.5
• Turbidity: <5 NTU
• Dissolved Oxygen (DO): >3 mg/L (varies by industry)
• Total Dissolved Solids (TDS): <500 mg/L
• Chemical Oxygen Demand (COD): <250 mg/L
• Biochemical Oxygen Demand (BOD): <30 mg/L
• Heavy Metals (Lead, Arsenic, Mercury): <0.01 mg/L

2. Power Plant Water Quality Standards

With their 40 CFR Part 423, EPA provides effluent limitation for the steam electric power generating industry. Similarly, a more specific organization, such as the ASME, provides a Boiler & Pressure Vessel Code (BPVC), which defines the particular requirements for boiler feedwater chemistry control in Section I:

• pH: 8.5 – 10.5
• Conductivity: <10 µS/cm (ultrapure water for high-pressure boilers)
• Silica: <0.02 mg/L (to prevent scaling)
• Dissolved Oxygen: <0.007 mg/L (to avoid corrosion)
• Total Hardness: <0.1 mg/L CaCO₃

3. Food & Beverage Industry Water Quality Standards

In the case of consumable items for humans, the criteria are far more restrictive. The control parameters are also different from typical powerplant or pharmaceutical requirements. It also means that the water quality sensors must be more accurate and precise in detecting. The FDA provides strict control for WQS with the parameters:

• pH: 6.5 – 8.5
• Hardness: <100 mg/L CaCO₃
• Chlorine Residual: 0.2 – 1.0 mg/L (to ensure proper disinfection)
• Total Coliforms: 0 CFU/100mL
• Turbidity: <1 NTU
• Nitrates & Nitrites: <10 mg/L (to avoid health hazards)

Water Quality Parameters

In the previous section, we observed the various chemical parameters that water quality sensors monitor to ensure quality output. Whether the water is meant for human consumption or any industrial process, it must control three key physical, chemical, and biological parameters.

While there are many parameters that water quality sensors can detect, there are some that are utilized in most industries. We will focus on the most popular and widely used parameters for water quality maintenance:

▪ Physical Parameters

▶ Temperature

Temperature is a critical parameter in most industrial applications. It can be vital in maintaining or enhancing chemical or biological reactions. Water quality sensors that detect temperature are usually online and provide direct information.

▶ Turbidity

Turbidity measures the clarity of water. Contaminants and suspended solids can make water murky or cloudy. Turbidity water quality sensors use infrared light to detect clarity.

▶ Total Suspended Solids (TSS)

Similar to turbidity detectors, suspended solids are also detected using light. The water quality sensor uses light passing through the water to detect suspended solids critical in food, beverage, pharmaceutical, and other crucial fields.

▶ Total Dissolved Solids (TDS)

Higher dissolved solids (TDS) indicate that the water may contain heavy metals or unwanted contaminants that require removal. It can affect the quality of aquatic life in rivers and lakes. The water will also retain more heat, which can affect marine life.

▶ Conductivity

Water quality sensors detect conductivity to calculate dissolved solids (ions). It can indicate the presence of contaminants that do not make the water murky or cloudy.

▶ Hardness

Measuring the amount of calcium and magnesium in water provides the degree of hardness. This parameter is vital as it can cause scale build-up and other damage to equipment. Water quality sensors use ion-selective electrodes to detect calcium and magnesium.

▶ Salinity

Water's density and heat capacity are vital properties. A water quality detector with electrical conductivity measurement can directly represent water salinity, which is a vital parameter in agriculture for irrigation and livestock.

▪ Chemical Parameters

◀ pH

Detecting the level of pH is vital in industrial, agricultural, and environmental applications. A lower pH can mean the water is too acidic, and a higher one means it is basic. The applications determine the required value of pH. For human consumption, water quality sensors need to detect between 6.5 and 8.5.

◀ Oxidation Reduction Potential (ORP)

The water's capability to oxidize or reduce is commonly referred to as redox or ORP. Water sensors that detect ORP provide insights into the presence of agents such as oxygen, chlorine, or hydrogen sulfide.

◀ Dissolved Oxygen

While ORP can measure potential oxygen levels, it is critical to detect dissolved oxygen levels in industrial water. Higher oxygen can damage carbon steel piping and equipment that uses oxidizing metal. For aquatic life, higher dissolved oxygen is desirable for survival. Electrochemical water quality sensors with a cathode (negative electrode) where oxygen reduces are used for detection.

◀ Ammonium Ion

Detecting and reducing the presence of ammonium ions is vital in aquatic ecosystems. Higher ammonium ion levels can reduce oxygen levels, harming aquatic life. Water quality sensors with Ion-Selective Electrodes (ISE) are the go-to choice for most online detection applications.

◀ Nitrate Ion

In drinking water, nitrate ions can be harmful to human consumption and cause problems like blue baby syndrome. In large water bodies, it can produce harmful algal blooms (HABs), which are harmful for the marine life. It is kept below low – 1 mg/L or less in aquaculture applications.

▪ Biological Parameters

▶ Chlorophyll Concentration

It represents the formation of algae and cyanobacteria within a water body. Water quality sensors detect these concentrations to indicate excessive algal growth or nutrient pollution. When excited with a specific wavelength of light, chlorophyll molecules emit light.

▶ Total Coliforms and E. coli

It is the prime indicator of fecal contamination in water, which can harm human health and lead to waterborne diseases. Detection is vital in the food, beverage, waste water treatment, and drinking water industries.

▶ Biological Oxygen Demand

Detecting biological oxygen demand using water quality sensors is vital to ensuring a controlled level of organic pollution. A higher biological oxygen demand can reduce the oxygen available to marine life. The paper, textile, and food industries monitor these parameters closely.

How to Measure Water Quality?

Measuring the water quality requires the use of online sensors or offline analysis techniques. Each of them have their own advantages and disadvantages. Here are the two testing techniques:

★ Laboratory Testing

All industries will have laboratory testing facilities, as they provide more accurate and precise values that can be critical for calibrating instrumentation and comparing results. These are vital for fulfilling regulatory requirements. However, they are slower and more costly for higher sampling volumes.

★ Field Testing

It is the widely adopted and accepted technique for detecting water quality. Various water quality sensors can be used to ensure enhanced supervision during the process. This fast and reliable technique produces reasonably accurate results for parameter control. However, it has the drawback of being moderately accurate.

Importance of Water Quality Sensors in Various Applications

The importance of sensor for water quality in agriculture, chemical, urban sewage, biodegradation, rivers, reservoirs, wells, water treatment, power plants, and many other applications canot be understated. Whether it is an industrial or environmental application, the use of water quality sensors will lead to better results and higher quality.

✔ Agricultural

In agricultural applications, water quality sensors are vital for greenhouse, irrigation, soil management, livestock, hydroponics, aquaponics, fertilizer management, and nutrient management. Parameters such as salinity, temperature, TSS, conductivity, ion presence, pH levels, dissolved oxygen, and BOD are vital to the health of livestock, crops, and the environment. Controlling these parameters also leads to higher crop yields and lower losses.

✔ Water Treatment

Facilites that treat water require biological, chemical, and physical parameter detection using water quality sensors. It ensures adherence to regulatory requirements. These water treatment plants can provide output for clean drinking water and wastewater treatment or provide water for industrial use. Controlling the water parameters such as DO, Coliform bacteria detection, BOD, pH, chlorine levels, nitrate, ammonium, oxidation-reduction potential (ORP), TDS, TSS, and turbidity will result in better efficiency, lower waste, and higher output.

✔ Process Plants

Process plants such as power plants, chemical plants, or refineries require stringent water quality monitoring to ensure operational efficiency, safety, and compliance with environmental regulations. Online water quality sensors are used for efficient operation while avoiding damage to equipment. Monitoring parameters such as pH, oxidation-reduction potential (ORP), chlorine, ammonium, and nitrate can help reduce the aging process and ensure reliability of equipment.

✔ Environmental

Whether it is its lakes, reservoirs, wells water, urban sewage, or any other environmental application. The use of online water quality sensors can provide live data acquisition that can reduce water pollution, balance the ecosystem, and ensure regulatory compliance. Physical, chemical, and biological parameters are all critical for monitoring the environmental impact. TSS, turbidity, and temperature help asses the condition of aquatic life. TDS, salanity, and conductivity provide pollution levels from industrial areas. Similarly, pH, ORP, nitrate, ammonium, and DO level control helps aquatic organisms. These are vital for the environment and sustainability.

Conclusion

Can we ensure water quality without using modern online sensors? The answer is no. Water quality sensors are now an integral part of all industrial and environmental applications. They provide intricate details into the process and ensure controlled products of the highest quality. Their purpose is to provide rapid online monitoring to the user to encourage head-on troubleshooting and process adjustments. They also ensure regulatory compliance to avoid potential legal actions.

Whether it measuring TSS,TDS, temerpatre, salinity, conductivity, turbidity, DO, ion concentrations, pH, ORP, or any other parameters, as we mentioned in our earlier sections, online water quality sensors get the job done with high accuracy and decent precision. We hope you have a better understanding of water quality standards and sensors and their importance.

If you are looking for high-end, long-lasting, affordable, and accurate online water quality sensors, visit the Rika Sensor website. They have over 10+ years of experience in developing sensors for various applications.