Starting up a 5-Stage Bardenpho Plant with In-Line Fermentation - One Step at a Time

The Cedar Creek Wastewater Treatment Plant (WWTP) was recently expanded and upgraded to meet new permit limits including annual average discharge concentrations of 8 mg/L total nitrogen (TN) and 1.5 mg/L total phosphorus (TP). The design of the new 5.25 mgd (19.9 MLD) facility is unique because the raw wastewater characteristics are variable and non-ideal for biological nutrient removal (BNR), with ratios of readily biodegradable chemical oxygen demand (RBCOD) to total Kjehldahl nitrogen (TKN) and TP ranging from 1.0 to 2.5, and 3 to 30, respectively. This necessitated the design to include carbon supplementation, and the City chose on-site fermentation as a sustainable solution that did not require purchasing chemicals. Since the Cedar Creek WWTP does not have primary clarifiers for conventional primary sludge fermentation, the design incorporates mixed liquor fermentation. The paper presents startup challenges including nitrification inhibition caused by collection system root killer treatments, and fermenter performance and design modifications.