Parts per million (PPM) is a standardized unit of measurement used to express the concentration of a substance within a solution. When testing water quality, PPM almost always refers to the Total Dissolved Solids (TDS) present in the water. TDS represents the combined weight of all dissolved inorganic salts, organic matter, and minerals. A higher PPM reading indicates a greater amount of these dissolved substances. Lowering these readings improves the aesthetic quality of water and reduces the concentration of potential contaminants.
Interpreting High PPM Readings
TDS is composed of various substances, including common inorganic salts like calcium, magnesium, sodium, and potassium, along with anions like chloride, sulfate, and bicarbonate. These solids originate from natural sources, such as the weathering of rocks and soil, or from human activities like agricultural runoff and industrial discharge. TDS is generally measured using a conductivity meter, which estimates the total ionic content by measuring how well the water conducts electricity.
High TDS levels affect the taste and appearance of water, often giving it a salty or bitter flavor. The World Health Organization (WHO) suggests that water below 300 PPM is considered excellent for palatability, while readings above 500 PPM are often considered high. Consistently high concentrations of dissolved solids can also lead to excessive scaling in appliances, hot water heaters, and pipes, which may shorten their service life.
A high PPM reading is a general indicator of water quality, not a direct measure of its safety. Many common dissolved solids, such as calcium and magnesium, are harmless minerals. The concern with elevated PPM is that it can signal the potential presence of specific, harmful contaminants like heavy metals, pesticides, or nitrates. Therefore, a high TDS reading suggests the need for further investigation into the water’s specific composition, especially if it exceeds 500 PPM.
Advanced Technologies for Significant Reduction
Achieving a substantial reduction in water PPM requires employing advanced filtration technologies that physically or chemically separate dissolved solids from water molecules. Reverse Osmosis (RO) is the most popular and effective method, utilizing a semipermeable membrane that acts as a highly selective filter. This membrane has extremely small pores, about 0.0001 microns, allowing water molecules to pass through while physically blocking up to 99% of dissolved salts, minerals, and contaminants.
The RO process works by applying pressure to the source water to overcome the natural osmotic pressure created by the difference in dissolved solids concentration. This forced flow drives the water through the membrane, leaving the concentrated solids to be flushed away. The system’s effectiveness, known as its rejection rate, typically ranges from 95% to 99% for Total Dissolved Solids. This makes RO capable of producing purified water with readings as low as 10 to 50 PPM from moderately high source water.
Water distillation achieves near-total reduction by changing the water’s phase. Water is boiled into steam, which leaves all non-volatile dissolved solids behind in the boiling chamber. The purified steam is then collected and condensed back into liquid form, resulting in water with an exceptionally low PPM.
Deionization (DI)
Deionization (DI) is a specialized method that uses ion-exchange resins to remove charged particles from the water. DI systems work by exchanging the positively charged ions (cations) and negatively charged ions (anions) with hydrogen and hydroxyl ions, respectively. These ions then combine to form pure water. DI is often used in laboratory or industrial settings where ultra-pure, ion-free water is required.
Accessible Methods and System Maintenance
While advanced systems deliver the lowest PPM, more accessible and cost-effective methods can provide a moderate reduction in dissolved solids and improve water quality. Activated carbon filters, commonly found in pitcher filters and under-sink units, work primarily through adsorption. The highly porous surface area of the carbon attracts and traps organic compounds, chlorine, and other substances that cause bad taste and odor.
Carbon filters are highly effective at removing compounds that affect aesthetics, but they generally do not significantly reduce the overall TDS level. This is because they are less effective at removing inorganic salts like calcium and magnesium. They improve the drinking experience by removing taste-altering substances, even if the measured PPM does not change dramatically. Gravity-fed pitcher filters, which often use a combination of carbon and ion-exchange media, offer a convenient, low-volume solution for modest improvements in water quality.
Maintaining any water filtration system is paramount to sustaining low PPM readings and ensuring the system’s longevity. Filters, particularly pre-filters and carbon blocks, must be replaced according to the manufacturer’s schedule, typically every six to twelve months, to prevent clogging and reduced efficiency. For RO systems, the semipermeable membrane usually requires replacement every two to three years. Regular maintenance also includes cleaning storage tanks and periodically checking the system for leaks or a drop in water pressure.