Composting toilets a misnomer: Excessive ammonia from urine inhibits microbial activity yet is insufficient in sanitizing the end-product

• End-product from 16 public mixed latrine style composting toilets (CTs) at 12 sites between 50 and 2100 m.a.s.l. in Western North America was tested in order to evaluate the effect of composting variables (TS%, NH3-N, temperature, and material age) on compost quality and hygiene (VS%, Escherichia coil, NO3--N, and pH). Principal component analysis indicated that TS%, temperature, and material age equally contributed to reduction in VS%. NH3-N had the greatest effect on NO3--N, E. coli, and pH. Nitrification was significantly inhibited above 386 mg/kg NH3-N, but no such limit was found for E. coil, despite a significant (p = 0.016) but weak (r(2) = 0.11) negative relationship. It may be possible to amplify the sanitizing effect of ammonia and overcome pathogen resistance due to low temperatures and re-contamination (caused by poor design) with generous dosing of urea and ash. However, even sanitized, the fertilization effect of discharged material on the natural environment may not be desired or permitted in parks or protected areas where many CTs were found. To this end, operators of CTs need to evaluate their primary management objectives and ensure congruency with proven system capabilities. (C) 2013 Elsevier Ltd. All rights reserved.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Annan naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Other Environmental Engineering (hsv//eng)

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