Pilot scale testing of salsnes filter (SF500) for biofilm solids removal from a full scale wastewater treatment plant

Abstract

This thesis investigated the performance of Salsnes Filter (SF) as a secondary treatment after biological treatment processes at Nordre Follo Renseanlegg (NFR) wastewater treatment plant. Wastewater from moving bed biofilm reactor (MBBR) from Reactor 5, was coagulated/flocculated and filtered on a prototype pilot scale SF500 filter. The investigation included use of PAX-18 aluminum inorganic coagulant, cationic polymers (C-496, C-490), and anionic polymer (A-130), in conjunction with flocculation. A bench scale SF apparatus was used for predictions and selecting optimum parameters for pilot scale coagulation/flocculation with SF fine mesh sieves sizes 250, 210, 158, 90, 54, 33 and 18 µm. Pilot scale testing on the prototype SF500 and on a SF1000 full scale filter were conducted after bench scale testing. PAX-18 and Superfloc C-496 were selected as optimum chemicals to be used on pilot scale coagulation/flocculation testing. Optimum G-value and flocculation time were of 67.8 s -1 and 10 min respectively were investigated and used. An optimum dosage of 94.6 mg Al/g TSS + 7.1 mg C-496/g TSS was used to achieve filtrate containing TP (< 0.3 mg/L), TSS (< 30 mg/L) and COD (< 50 mg/L), for removal efficiency of 96%, 98% and 88% respectively, using a 33µm fine mesh sieve. The pH change, filtration rate and power consumption in the process were also monitored. Particle size characterization of raw NFR primary (degritted) wastewater and MBBR biofilm wastewater were also investigated using FlowCAM and Malvern Mastersizer 3000 after bench scale SF apparatus with sieve openings from 350 to 18 µm. The SF1000 was also used for NFR primary (degritted) wastewater characterization investigationswith both 33 µm and 350 µm fine mesh openings.