Assessment of free nitrous acid pre-treatment on a mixture of primary sludge and waste activated sludge: Effect of exposure time and concentration.
Free nitrous acid (FNA) has been shown to enhance the biodegradability of waste activated sludge (WAS) but its effectiveness on the pre-treatment of mixed sludge is not known. This study explores the effectiveness of four different FNA concentrations (0, 2.49, 3.55, 4.62mgN-HNO2/L) and three exposure times (2, 5, 9h) lower than the ones reported in literature (24h) on WAS characteristics and specific methane production (SMP). FNA pre-treatment reduced sludge cell viability below 10% in all cases after an exposure time of 5h, increasing the solubility of the organic matter. The treated mixed sludge was used as substrate for the biochemical methane production tests to assess its SMP. Results showed a significant increase (up to 25%) on SMP when the sludge was pretreated with the lowest FNA concentration (2.49mgN-HNO2/L) during 2 and 5h but did not show any improvement at longer exposure times or higher FNA concentrations.
Catalan Institute for Water Research (ICRA), Emili Grahit Street, 101, H(2)O Building, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain.
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Zahedi
Department of Innovation and Technology, FCC Aqualia, Balmes Street, 36, 6th Floor, 08007 Barcelona, Spain.
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Icaran
Advanced Water Management Centre, The University of Queensland, St Lucia 4072, Australia.
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Z
Yuan
Catalan Institute for Water Research (ICRA), Emili Grahit Street, 101, H(2)O Building, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain. Electronic address: mpijuan@icra.cat.
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Pijuan
D019149:Bioreactors; D009608:Nitrous Acid / Q000032:analysis*; D012722:Sewage / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D012722:Sewage; D009608:Nitrous Acid
Anaerobic digestion; Free-nitrous acid pre-treatment; Methane production; Mixed sludge; Sludge biodegradability