Oxygen has played a key role in the treatment of drinking water and wastewater for over 40 years. The estimated current global consumption of oxygen in these applications is around 15,000 tons per day. In the US, about 20 percent of municipal drinking water and 50 percent of municipal wastewater is treated with processes that rely on oxygen.
The industrial gas industry has been a driving force in the development and introduction of oxygenbased water and wastewater treatment processes and technologies, with Air Products (www.airproducts.com) a recognized leader from the beginning. As environmental and population demands increase, we see continued growth and innovation in this market.
Municipal Wastewater Treatment
Municipal wastewater contains contaminants that impact the environment: solids; materials that remove oxygen from water, referred to as biological oxygen demand or BOD; and nutrients, such as nitrogen and phosphorus, which promote algae growth. Today, most wastewater treatment facilities consist of primary treatment—the removal of solids by settling and skimming—followed by secondary treatment— BOD removal using naturally occurring bacteria. Advanced processes also include treatment for nutrient removal or water reuse.
One of the most significant environmental improvements of the 20th century was the introduction of secondary wastewater treatment and, in particular, the activated sludge process. This process uses large, well-mixed basins to hold wastewater while bacteria, in the form of sludge, consume BOD. The bacteria require significant amounts of oxygen. Water discharged from the basins passes to a clarifier to settle out bacteria sludge prior to discharge.
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