ABSTRACT
A continuous supercritical water oxidation reactor was designed and constructed to investigate the conversion of a feces simulant without the use of a co-fuel. The maximum reactor temperature and waste conversion was determined as a function of stoichiometric excess of oxygen in order to determine factor levels for subsequent investigation. 48% oxygen excess showed the highest temperature with full conversion. Factorial analysis was then used to determine the effects of feed concentration, oxygen excess, inlet temperature, and operating pressure on the increase in the temperature of the reacting fluid as well as a newly defined non-dimensional number, NJa representing heat transfer efficiency. Operating pressure and stoichiometric excess oxygen were found to have the most significant impacts on NJa. Feed concentration had a significant impact on fluid temperature increase showing an average difference of 46.4°C between the factorial levels.
Subject(s)
Feces/chemistry , Sewage/chemistry , Water Purification/methods , Water/chemistry , Equipment Design , Hot Temperature , Models, Theoretical , Oxidation-Reduction , Oxygen , Pressure , Water Purification/instrumentationABSTRACT
Anaerobic ammonium oxidizing (anammox) bacteria based technologies are widely applied for nitrogen removal from warm (25-40 °C) wastewater with high ammonium concentrations (â¼1 gNH4-N L(-1)). Extension of the operational window of this energy and resource efficient process is restricted by the "supposed" low growth rate of the responsible microorganisms. Here we demonstrate that the maximum specific growth rate (µ(max)) of anammox bacteria can be increased to a µ(max) value of 0.33 d(-1) by applying a novel selection strategy based on the maximization of the electron transfer capacity in a membrane bioreactor. This value is four times higher than the highest previously reported value. The microbial community was strongly dominated by anammox bacteria closely related (99%) to Candidatus Brocadia sp.40 throughout the experiment. The results described here demonstrate the remarkable capacity of a phylogenetically stable anammox community to adjust its growth rate in response to a change in the cultivation conditions imposed.
