Water quality impacts daily life, influencing everything from the taste of drinking water to the health of garden plants. Understanding the concentration of dissolved substances in water is important for managing its quality effectively. This concentration is commonly measured in parts per million, or PPM, which indicates the quantity of dissolved materials present in a given volume of water. What constitutes a desirable PPM level is not universal; it depends entirely on the water’s intended application.
Understanding Parts Per Million
PPM quantifies Total Dissolved Solids (TDS) in water, encompassing inorganic salts and small amounts of organic matter. These dissolved solids include beneficial minerals like calcium, magnesium, sodium, and potassium, and other components such as chlorides, sulfates, nitrates, and bicarbonates. TDS stems from both natural sources, like water flowing through rocks and soils, and human activities such as agricultural runoff or industrial wastewater. While some dissolved solids are essential and enhance taste, others, like heavy metals, can be undesirable or harmful.
Measuring Water PPM
Water PPM is typically determined using a TDS meter, a compact device that measures electrical conductivity. Dissolved solids, particularly salts and minerals, carry an electrical charge, increasing water’s conductivity. The meter converts this reading into an estimated PPM value. To use it, immerse the electrodes into the water sample, ensuring only the tip is submerged. After a few seconds, the PPM value will display, and periodic calibration with a standard solution ensures accuracy.
Recommended PPM Levels for Common Uses
Drinking Water
For drinking water, TDS levels influence palatability and safety. The World Health Organization (WHO) suggests water under 300 PPM is excellent for taste, while 300-600 PPM is good. The U.S. Environmental Protection Agency (EPA) has a secondary guideline of 500 PPM for aesthetic concerns like taste. Water below 50 PPM can taste flat, while over 500 PPM may have an unpleasant metallic or bitter taste. High TDS levels are not always a direct health risk, but can indicate other contaminants.
Plants
For plants, optimal water PPM depends on the plant type and growth stage, as it relates to nutrient concentration. Young seedlings need 350-500 PPM. As plants mature, vegetative growth requires 650-900 PPM, increasing to 900-1150 PPM during flowering or fruiting. For soil-grown plants, nutrient solution PPM ranges from 400-600 PPM for seedlings to 800-900 PPM for vegetative growth. These are general guidelines, and specific plant needs may vary.
Managing Water PPM
Water’s PPM levels can fluctuate due to various factors, including the quality of the original source water, the materials in plumbing systems, and environmental conditions like evaporation. For instance, water flowing through mineral-rich ground will naturally have higher TDS. Evaporation concentrates dissolved solids, leading to an increase in PPM over time. Adjusting water PPM involves either reducing or increasing the concentration of dissolved solids.
Reducing PPM
To reduce high PPM, common methods include reverse osmosis (RO) filtration, which lowers TDS by removing dissolved particles. Distillation separates pure water from dissolved solids by boiling and condensing steam. Ion exchange systems also reduce PPM by replacing undesirable ions, often used in water softening. For hydroponic systems, adding pure water can dilute the nutrient solution and lower PPM.
Increasing PPM
Conversely, to increase PPM, particularly for plant growth, nutrient solutions or mineral supplements are added to the water. For drinking water that is excessively pure, remineralization filters can introduce beneficial minerals to achieve a more balanced and palatable PPM.