THE USE OF ORGANIC FRACTION OF MUNICIPAL SOLID WASTE HYDROLYSIS PRODUCTS FOR BIOLOGICAL NUTRIENT REMOVAL IN WASTEWATER TREATMENT PLANTS P. LLABRES 1 , P. PAVAN 2 , P. BATTISTIONI 3* M , F. CECCHI 4 and J. MATA-ALVAREZ 1 * * M 1 Department of Chemical Engineering, University of Barcelona, MartõÂ i FranqueÁs, 1, Pta. 6, 08028 Barcelona, Spain; 2 Department of Environmental Sciences, University of Venice, Dorsoduro, 2137 Venice, Italy; 3 Institute of Hydraulics, Engineering Faculty, University of Ancona, 60131 Ancona, Italy and 4 Department of Chemistry, Chemical Engineering and Materials, University of L'Aquila, Monteluco di Roio, 67100 L'Aquila, Italy (First received June 1997; accepted in revised form April 1998) AbstractÐExperiments in a continuous UCT-bench scale plant using synthetic wastewater, have been carried out to demonstrate the feasibility of using the biodegradable organic fraction of municipal solid waste (BOF-MSW) as an easily biodegradable C source for nitrogen and phosphorous removal. Yields obtained are quite good and the additional load introduced by the use of the fermentation products of the BOF-MSW can be considered negligible. In addition, the basic mass balances carried out, show that the amount of easily biodegradable C-source needed to treat the wastewater produced by a given unit of persons can be obtained from the amount of BOF-MSW generated by this unit. # 1998 Else- vier Science Ltd. All rights reserved Key wordsÐbiological nutrient removal, fermentation, organic fraction, municipal solid waste, phos- phorus, denitri®cation NOMENCLATURE BNR biological nutrient removal BOF-MSW biodegradable organic fraction of municipal solid waste COD chemical oxygen demand (mg O 2 l À1 ) d day EBPR enhanced biological phosphate removal HRT hydraulic retention time (time units, days or hours) MLVSS mixed liquor volatile suspended solids (mg VSS l À1 ) MSW municipal solid waste RBCOD readily biodegradable COD (mg O 2 l À1 ) SBCOD slowly biodegradable COD (mg O 2 l À1 ) SDR speci®c denitri®cation rate (mg N l À1 d À1 g VSS À1 ) TCOD total chemical oxygen demand (mg O 2 l À1 ) TN total nitrogen (mg l À1 ) TKN total Kjeldhal nitrogen (mg l À1 ) TP total phosphorous (mg l À1 ) TS total solids (g kg À1 ) TVFA total volatile fatty acids (mg l À1 ) TVS total volatile solids (g kg À1 ) UCT University of Cape Town VFA volatile fatty acids (mg l À1 ) VSS volatile suspended solids (mg l À1 ) WWTP wastewater treatment plant WW-1 wastewater type 1 WW-2 wastewater type 2 INTRODUCTION Phosphate and nitrogen contained in sewage can cause eutrophication in closed water bodies such as lakes, ponds and inland seas. Phosphorous is recog- nized as one of the major elements contributing to this phenomenon. Enhanced biological phosphate removal (EBPR) from wastewater, a biological alternative to chemical phosphate precipitation, is based on the enrichment of activated sludge with polyphosphate accumulating bacteria. During the anaerobic stage, phosphate removing bacteria con- sume readily biodegradable carbon, often denoted as readily biodegradable COD (RBCOD). The concentration of RBCOD aects the e- ciency of biological nutrient removal (BNR) pro- cesses. When it is too low, the addition of an external RBCOD source such as methanol is necess- ary. Other methods are based on the internal C- sources, obtained through the hydrolysis of the re- cycled sewage sludge. In order to enhance biological nutrient removal and improve process operation, acid fermentation of primary sludges has been used in some plants to produce RBCOD for BNR (Skalsky and Daigger, 1995). Wat. Res. Vol. 33, No. 1, pp. 214±222, 1999 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0043-1354/98 $ - see front matter PII: S0043-1354(98)00179-1 *Author to whom all correspondence should be addressed. [Tel: +34-93-4021305; Fax: +34-93-4021291; E-mail: jmata@medicina.ub.es]. 214