Modeling Strategy for SBR Recovery after Upset
The paper presents results of treatability study on wastewater highly contaminated with ammonia (800 mg/l), (phenols (300 mg/l), thiocyanate (210 mg/l), and arsenic up to 11 mg/l. The study was conducted in two sequencing batch reactors (SBRs) using biomass from a coke plant. After two months of acclimatization the biomass was able to remove ammonia to below 1 mg/l and phenols and thiocynate below detection limits. In order to develop a strategy for SBR recovery, two different upset conditions were induced. During the first upset aeration was terminated while continuing feeding. The second upset was implemented by increasing pH to ~ 11.0. During both upsets nitrification was significantly affected while the removal of phenols and cyanide was practically unchanged. Recovery procedure included increasing temperature, washing with water and seeding with unaffected biomass, and it the case of the second upset, also a pH adjustment. More flexibility of nitrification system for overloading than for an pH upset was observed. It has been found that dissolved oxygen (DO) profile during a feed cycle is a good indicator of upsetting conditions and allows monitoring SBR biomass recovery. Based on DO profile, upsetting conditions can be early detected and recovery measures quickly applied.