An economic appraisal of using source separation of human urine to contain and treat endocrine disrupters in the USA.

Elevated concentrations of estrogens in natural waters pose a significant threat to public health and aquatic ecosystems. Both natural (estrone, 17β-estradiol and estriol) and synthetic (17α ethynylestradiol) estrogens, ubiquitous in wastewater effluents and receiving waters, have been shown to affect the endocrine system of human and aquatic life. The effects vary from cancer to sex reversals at levels as low as parts per trillion in sensitive organisms. Separation of urine, which constitutes only about 1% of domestic sewage and contains nearly all of the excreted estrogens, potentially offers an energy-efficient way to contain and then treat these chemicals. With a capital expense of $2100 and operation and maintenance costs of $69 per year for a urine diverting toilet system, a family in the USA can realize estimated savings of $101 per year in energy, water, and nutrients and a decrease of 100 kg in greenhouse gas emissions. To remove 99% of estrogenicity in discharged waters would require approximately 12 kW h per year using continuous electrodialysis followed by ozonation (O(3)) of source separated urine. To achieve the same results by adding O(3) treatment after activated sludge at existing municipal wastewater treatment plants would require 23 kW h per year. From an energy standpoint it makes sense to practice source separation and treatment of urine to limit estrogen discharges into the environment.