Tools for drinking water reuse and treatment: Aluminum Sulfate coagulation optimization for ultrafiltration membrane pre-treatment using raw surface water blended with ultrafiltration permeate

Abstract

COBLER, DALE. MASTER OF ENVIRONMENTAL ASSESSMENT. TOOLS FOR DRINKING WATER REUSE AND TREATMENT: ALUMINUM SULFATE COAGULATION OPTIMIZATION FOR ULTRAFILTRATION MEMBRANE PRE-TREATMENT USING RAW SURFACE WATER BLENDED WITH ULTRAFILTRATION PERMEATE. The primary objective of this study was to identify an optimum aluminum sulfate (alum) coagulation dosing range for pre-treatment of supply water going to an ultrafiltration (UF) membrane system. The supply water assessed consisted of raw surface water (80-90%) blended with ultrafiltration permeate (10-20%). The ultrafiltration permeate used for blending was provided from a secondary ultrafiltration membrane system which recycles Spent Filter Backwash Water (SFBW) generated from conventional granular media filters and the primary ultrafiltration membrane system. Jar testing was completed using blended samples coagulated with alum and settled for a total time of two hours to simulate regulated detention time. The water quality parameter of key interest was the removal of organics as indirectly determined via ultraviolet wavelength absorbance spectrophotometric measurements at 254 nanometers (UVA254). The alum coagulation optimization was selected as a critical method for removal of disinfection by-product (DBP) pre-cursors present in Natural Organic Matter (NOM) which are introduced to the system in the raw surface water. Alum coagulation optimized dosage ranges were between 7-8.5 mg/L for all blended samples. Jar Testing results indicated that introduction of alum coagulation pre-treatment to the primary UF membrane system, achieved organics removal that would be comparable to the conventional treatment system.