Water Quality

Sewage pollution contains chemical contaminants and many types of harmful bacteria, parasites, and viruses that can make swimmers sick. Swimmers who come into contact with wastewater pollution can develop gastroinestinal illness and various infections. Click HERE to learn what types of microorganisms you may encounter in sewage-contaminated water. Where does sewage pollution come from in Hawai'i?

Cesspools are a substandard waste disposal method in which household wastewater is discharged into a hole in the ground with no treatment. Over 88,000 cesspools in Hawai'i discharge more than 53 million gallons of sewage into the ground every day. This pollution can reach groundwater, streams and the coastal ocean, spreading pathogens into the environment and making waters unsafe for swimming. The nutrients and contaminants in wastewater are harmful to coral reef ecosystems and drinking water quality.

Septic systems, while better than cesspools, still cause nutrient pollution in the environment via nutrient rich effluent that is disposed of in the leach field. Excess nutrients can cause invasive algae to overgrow coral reefs, and high nitrate in drinking water is associated with higher rates of certain cancers. Click HERE to check out some advanced pollution-reducing technologies to replace cesspools and septic systems.

Injection wells and private wastewater treatment plants are another source of sewage contamination. Injection wells discharge treated wastewater underground, as opposed to an ocean outfall, but the wastewater has been shown to enter the reef environments nearby via groundwater. The sheer volume of effluent contributes to high pollutant loading and negative effects on the coral reef in many areas of Hawaiʻi, including Lahaina, the focus of a recent Supreme Court case.

Municipal sewer spills, leaks, and failures are caused by corrosion, sewage infiltration to groundwater, groundwater infiltration to overwhelmed treatment facilities, and limits in sewer line capacity. Aging infrastructure is a major challenge for Hawai'i and has created a persistent and pervasive water quality hazard.

Invasive animals contribute to water pollution by harming and uprooting native plants, which increases sedimentation, and by introducing their waste products to the watershed. Pigs, goats, deer, feral cats, and other mammals were introduced to Hawai'i and have negative impacts on the native forest ecosystem. In addition to physical damage to native forests, these invasive animals spread Leptospirosis and Cryptosporidiosis, which cause illness in humans. Family groups of feral pigs leave significant amounts of urine and feces in and around the water at wallow sites, and silt, excrement and potentially harmful pathogens are washed downstream. Decomposing carcasses represent an additional water quality threat.

Erosion in Hawai'i is aggravated by invasive ungulates (deer, pigs, goats), degradation of native vegetation, and invasive plants. Additionally, unsustainable land use and improper soil management in agriculture increase sediment runoff into streams and nearshore oceans. High rates of erosion occur in areas where precipitation is high, slopes are steep and vegetation cover is poor. Sediment pollutants occur as siltation, suspended solids, turbidity, nutrients, and pathogens. Suspended sediments reach coastal ocean waters and cause light limitation and damage to benthic organisms such as corals and native limu.

Major agricultural contributors to water pollution in Hawai'i are nutrients, herbicides & pesticides, organic matter, sediments, pathogens, and drug residues. Rain, flooding, and groundwater flush agricultural pollutants towards the ocean. Nutrients from fertilizer negatively impact coral reefs. Organic matter from animal excreta, uneaten animal feed, animal-processing industries, and mismanaged crop residues can all be significant water pollutants. Livestock excreta contain many zoonotic microorganisms and multicellular parasites that can be harmful to human health. New agricultural pollutants such as antibiotics, growth promoters, and hormones also pose a threat. The discharge of organic matter increases the risk of eutrophication and algal blooms.

Stormwater is a major mechanism by which pollutants reach streams and oceans. Stormwater pollutants enter a body of water due to water flowing over the surface of the land and carrying pollutants with it. These pollutants include agricultural and residential fertilizers, agricultural pollutants and animal wastes, oil, grease, heavy metals, and litter. Increased wildfires, forest loss, invasive plants, urbanization and stream hardening all increase the amount of sediment and pollutants that reach the ocean via stormwater.