title: Effects of pH and precipitation on autohydrogenotrophic denitrification using the hollow-fiber membrane-biofilm reactor.
abstract: Experiments carried out in a hollow-fiber, membrane-biofilm reactor (HFMBR) showed that the optimum pH for autotrophic denitrification was in the range 7.7-8.6, with the maximum efficiency at 8.4. Increasing the pH above 8.6 caused a significant decrease in nitrate removal rate and a dramatic increase in nitrite accumulation. The pH rose by 1.2 units when a large buffer was not added, suggesting that some field applications may require pH control. Precipitation of Ca(2+) occurred in every experiment. Precipitation was the largest sink for carbonate, and it also offset alkalinity production by denitrification. Although the alkalinity increased in most cases, systems with a high carbonate buffer and high pH accentuated precipitation, and the net change in alkalinity was negative. The long-term success of field applications of the HFMBR may depend upon the interactions among calcium concentration, total carbonate concentration, pH, and alkalinity changes.
authors.affiliation: Department of Civil Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3109, USA. lee.kc@pg.com
authors.forename: Kuan-Chun
authors.initials: KC
authors.lastname: Lee
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D018441:Biofilms; D019149:Bioreactors; D002119:Calcium Carbonate / Q000737:chemistry; D011232:Chemical Precipitation; D005374:Filtration; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D009566:Nitrates / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014865:Waste Disposal, Fluid; D018508:Water Purification / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D009566:Nitrates; D002119:Calcium Carbonate