Most is applied to agricultural sites, with minor amounts applied to forestry and reclamation sites (e.g., Superfund and brownfield lands) and urban area (e.g., maintaining park land). management practices amount to 54% of biosolids being beneficially used. Qualified biosolids can be beneficially used after “stabilization,” which kills pathogens and decomposes vector-attractive substances.16 Many of these chemicals are not removed by POTWs. 15 Some of these chemicals are endocrine disruptors, a class of compounds that alter the normal functioning of endocrine systems, including those that affect growth and reproduction. 14 Polybrominated diphenyl ethers (PBDEs) and per- and polyfluoroalkyl substances (PFASs) have become CECs due to their wide distribution and persistence in the environment. Classes of unregulated compounds known as “contaminants of emerging concern” (CECs) are a concern for water treatment engineers, particularly pharmaceuticals and personal care products.However, their production and transport have life cycle impacts. Chemical additions of ferric salts and lime enhance coagulation and sedimentation processes for improved solids removal as well as removal of toxic pollutants.However, this method can have higher maintenance, energy and capital costs. Ultraviolet (UV) disinfection is an alternative to chlorination that does not add chemicals to the water.Chlorination may be followed by dechlorination to avoid deteriorating ecological health of the receiving stream and the production of carcinogenic by-products. In the U.S., chlorination is the most common mean of disinfection. 9 Sludge requires significant energy to treat-about one-third of total electricity use by a wastewater treatment system. POTWs generate over 13.8 million tons (dry weight) of sludge annually.It has set ambitious goals to increase water recycling, with at least 1.5 million ac-ft/yr recycled by 2020, and 2.5 million ac-ft/yr by 2030. In 2015, California recycled roughly 714,000 acre-feet of water per year (ac-ft/yr).6 Use of reclaimed water for consumption is becoming more common, particularly in regions prone to drought or with growing water demand (such as the U.S. An estimated 14,748 POTWs provide wastewater collection, treatment, and disposal service to more than 238 million people.3 Failing septic systems may contaminate surface and groundwater. Over 16% of households are not served by public sewers and usually depend on septic tanks to treat and dispose of wastewater.Excess nutrients can come from agriculture, urban runoff, and wastewater treatment and cause water quality problems, such as algal blooms and fish kills.In the U.S., 58% of river and stream miles, 40% of lake acres, 17% of estuarine square miles, and 23% of Great Lakes shoreline miles that have been assessed by the U.S.Pollutants contaminate receiving water via many pathways: point sources, non-point sources (e.g., air deposition, agriculture), sanitary sewer overflows, stormwater runoff, combined sewer overflows, and hydrologic modifications (e.g., channelization and dredging).In addition, much of the existing wastewater infrastructure, including collection systems, treatment plants, and equipment, has deteriorated and is in need of repair or replacement. Despite the improvement in effluent quality, point source discharges continue to be a significant contributor to the degradation of surface water quality. Since the early 1970s, effluent water quality has been improved at Publicly Owned Treatment Works (POTWs) and other point source discharges through major public and private investments prescribed by the Clean Water Act (CWA). For many years, humans have treated wastewater to protect human and ecological health from waterborne diseases.
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