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Liquid Waste Disposal Methods

Liquid waste is classified as waste water containing less than 1 percent of solid matter. Its proper disposal is essential for the maintenance of human and animal health. Liquid waste generally has a high concentration of dissolved compounds such as metals and salts. Before liquid waste can be disposed of, it must first be analyzed to determine whether or not it may be hazardous.

  1. Dewatering and Sedimentation

    • Dewatering can be applied when dealing with nonhazardous liquid waste. Water is extracted, leaving behind the solid components such as metals, oil, grease and other organics. Solid contaminants can be removed by the use of a sediment basin, which is a basin fitted with a controlled-release structure and set up in an embankment where it filters sediment, allowing it to settle at the bottom of the basin. The remaining liquid can be further filtered or chemically neutralized prior to disposal. A permit from the appropriate local agency is usually required to carry out this type of disposal. This method is useful when removing water from construction sites.

    Root Zone Treatment Method

    • Liquid waste derived from humans such as toilet, bath and kitchen water can be disposed of using the root zone treatment method. This method employs a sedimentation tank to retain solids, inlet and outlet pipes to permit water-flow, inflow and outflow collection systems, a filtration technique such as gravel filtration, and a polishing pond, which is the last purification stop before the water is either released into the natural environment or recycled into a water treatment system. The polishing pond is where bacteria and other microbial contaminants are likely to be removed.

    Incineration

    • Most solid sediments extracted from liquid waste are disposed of in landfills and underground storage tanks, depending on their hazard level. This can, however, become a major source of pollution. Another method of disposing waste water solids is incineration. This utilizes high temperatures to thermally process solid sediments in the presence of air, once all water has been extracted. Two common incineration systems are multiple hearth furnaces and fluidized bed furnaces. Each system must be fitted with air pollution control equipment to control emission of harmful gases such as nitrogen oxides and carbon monoxide.

    Composting

    • In cases of organic waste, waste water solids can be disposed of by composting. This method transforms solid sediments to an organic fertilizer. Composting removes pathogens and produces an effective product containing important nutrients such as potassium and nitrogen used as fertilizers, which can improve the ability of soil to retain nutrients.

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