ΔΙΒΑΘΜΙΑ ΒΙΟΛΟΓΙΚΑ ΦΙΛΤΡΑ

Abstract

A STEADY-STATE MATHEMATICAL MODEL OF THE BIOLOGICAL FILTER WITHOUT RECIRCULATION WAS DEVELOPED WITH THE AID OF QUALITATIVE AND QUANTITATIVE THEORETICAL CONSIDERATIONS AND EMPIRICAL ASSUMPTIONS. THE MODEL WAS CALIBRATED AND VALIDATED WITHTHE AID OF PERFORMANCE DATA FROM 2 TWO-STAGE PILOT-SCALE FILTERS OPERATED IN PARALLEL IN THE RANGE OF THE LOW AND INTERMEDIATE OVERFLOW RATES (1-8 M.D-1). THE FOLLOWING PERFORMANCE RELATIONSHIP FOR ONE AND TWO-STAGE FILTERS WITHOUT INTERMEDIATE SETTLEMENT, WITH TOTAL DEPTH H IN METERS AND TEMPERATURE 20 C WAS DERIVED: CE=5.1+0. 8368CO{1+0.3555Q0.01CO0.62H-0.00403Q0.91CO1.05H}-1 WHERE CO AND CE ARE THE INFLUENT AND EFFLUENT BOD5 CONCENTRATIONS IN MG.1-1 AND Q IS THE OVERFLOW RATE OF THE FILTER IN M.D-1. DUE TO THE CONTROLLED OPERATION OF THE PILOTPLANT, THE DERIVED PERFORMANCE RELATIONSHIP SHOULD BE CONSIDERED AS DESCRIBINGTHE PERFORMANCE OF BIOLOGICAL FILTERS WITH FAVOURABLE "SECONDARY FACTORS", THAT IS, WITH GOOD PRIMARY AND FINAL SETTLING, EFFECTIVE DISTRIBUTION SYSTEM AND APPROPRIATE DOSING REGIME. THE PERFORMANCE RELATIONSHIP WAS FOUND TO BE IN GOOD AGGREMENT WITH PUBLISHED PILOT-SCALE DATA AND ALSO WITH PERFORMANCE DATA FROM FULL-SCALE FILTERS CHARACTERIZED BY RELATIVELY HIGH EFFICIENCY WHICH MIGHT BE ATTRIBUTED TO FAVOURABLE SECONDARY FACTORS. SUPPOSING THAT THE SECONDARY FACTORS CAN BE FAIRLY EASILY OPTIMIZED, THE BIOLOGICAL FILTER MAY HAVE SIGNIFICANT ECONOMICAL ADVANTAGE OVER THE ACTIVATED SLUDGE SYSTEM, EVEN FOR HIGH BOD REMOVAL EFFICIENCIES IN ORDER TO EXAMINE THE EFFECT OF THE RECIRCULATION ON THE PERFORMANCE OF THE FILTER THE TWO LINES OF THE TWO-STAGE FILTERS OPERATED, DURING THREE PERIODS OF OPERATION OF THE PILOT PLANT, WITH THE SAME OVERFLOW RATE BUT DIFFERENT RECIRCULATION RATIOS (R=0 AND 1 RESPECTIVELY). THE PERFORMANCE DATA SHOWED THAT RECIRCULATION, WITH R=1, HAD NO SIGNIFICANT EFFECT ON BOD OR AMMONIA REMOVAL.