In the context of water quality, the term “hormones” primarily refers to a class of trace contaminants known as Endocrine Disrupting Chemicals (EDCs). These are synthetic and natural compounds that interfere with the endocrine system of humans and wildlife. EDCs and pharmaceutical residues are present at extremely low concentrations, often measured in nanograms per liter (parts per trillion). Despite these low levels, they pose a public health concern due to their potent biological activity. The worry stems from the potential for chronic, low-level exposure to disrupt hormonal balance, which regulates growth, development, metabolism, and reproduction. Addressing these emerging contaminants requires understanding their origin and the advanced technologies necessary for their removal.
Sources and Types of Hormones in Water
Endocrine Disrupting Chemicals enter the water supply through several distinct pathways because conventional wastewater treatment is not designed to remove them completely. A primary source is the human excretion of pharmaceuticals, including birth control medications, hormone replacement therapies, and other therapeutic drugs. These active compounds pass through the body and enter the sewer system, ultimately making their way into rivers and water sources.
Another significant contributor is agricultural runoff, which includes livestock steroids used to promote growth and a range of pesticides that exhibit endocrine-disrupting properties. When rain or irrigation water drains from fields, it carries these chemicals into surface water and groundwater reservoirs.
Industrial wastewater discharge also introduces a wide array of synthetic EDCs into the environment, including chemicals like Bisphenol A (BPA) and phthalates, which are used in plastics and manufacturing. These synthetic compounds are the main concern, as they can mimic or block natural hormones. While natural estrogens like estrone and estriol are also found, they degrade more readily than the persistent synthetic variants like 17α-ethinylestradiol (EE2), a component of many oral contraceptives.
Large-Scale Water Treatment Methods
Municipal water treatment facilities often employ advanced technologies to eliminate trace EDCs and pharmaceutical residues. These solutions move beyond standard filtration and disinfection to actively break down or capture these complex molecules.
Ozonation
Ozonation introduces ozone gas (\(\text{O}_3\)) into the water. Ozone is a powerful oxidant that chemically reacts with the molecular structure of EDCs, particularly those with electron-rich functional groups like phenols and amines. This process breaks the complex molecules down into smaller, less harmful by-products, achieving removal rates greater than 90% for many EDCs and pharmaceuticals. Ozonation is sometimes employed as an initial treatment step to oxidize contaminants before they reach other filtration stages.
Granular Activated Carbon (GAC) Filtration
GAC filtration relies on the process of adsorption, where highly porous carbon material traps organic contaminants on its vast internal surface area. The effectiveness of GAC is determined by the size and polarity of the compound, with larger, more hydrophobic EDC molecules tending to adsorb more strongly. GAC is effective at removing a wide variety of trace organic contaminants. However, its performance can be negatively impacted by natural organic matter (NOM), which competes for adsorption sites and reduces the carbon’s capacity over time.
Advanced Oxidation Processes (AOPs)
AOPs often involve combining ozone with hydrogen peroxide (\(\text{H}_2\text{O}_2\)) or ultraviolet (UV) light. This combination generates highly reactive hydroxyl radicals (\(\cdot\text{OH}\)), which are significantly more potent oxidizers than ozone alone. The hydroxyl radicals react non-selectively with nearly all organic compounds, ensuring a comprehensive breakdown of even the most recalcitrant EDCs. While AOPs can achieve near-complete removal, they are more energy-intensive and costly to implement than standard ozonation.
Household Filtration Options
For consumers looking to reduce their exposure to trace EDCs at the tap, several advanced household filtration systems offer confirmed removal capabilities.
Reverse Osmosis (RO) Systems
RO systems are typically installed under the sink to treat drinking water and are the most effective option. RO works by forcing water under pressure through a semipermeable membrane that physically blocks nearly all dissolved solids, including EDCs and pharmaceutical residues. RO systems typically achieve greater than 95% removal of contaminants, including hormones. While they are slower and produce wastewater, the initial cost for a point-of-use RO system can range from $150 to $600, with annual filter replacement costs averaging between $50 and $250. Installation is generally more complex than with other home filters, often requiring a connection to the drain line.
Activated Carbon Filters
The effectiveness of activated carbon filters against EDCs varies significantly based on the filter type. Simple pitcher or faucet-mounted filters provide only limited contact time and are less effective at removing EDCs than chlorine or taste contaminants. Solid-block carbon filters compress the carbon into a dense block, forcing water through a more tortuous path. This design dramatically increases the contact time and surface area, allowing for much higher rates of adsorption for EDCs, often certified to remove specific pharmaceutical contaminants.
Distillation
Distillation offers another highly effective method for removing non-volatile contaminants like hormones. The process involves boiling the water and then condensing the purified steam back into a liquid, leaving all dissolved solids behind. While distillation produces nearly pure water, it is the slowest method, often yielding only a few gallons per day. Distillation units are typically countertop models, costing between $100 and $500, with a low maintenance cost mainly involving cleaning the boiling chamber.