Analysis of a full-scale high-rate activated sludge system and second stage nitrifying biological aerated filter using modeling methods and fluorescent in-situ hybridization.

摘要

A current challenge to the civil/environmental engineering field is to assist full-scale wastewater treatment facilities through wider use of advances in modeling methods and analytical techniques. To address this challenge I applied modeling tools and, with assistance, the molecular biology analytical method of Fluorescent In-Situ Hybridization (FISH) to the high rate activated sludge process and the second stage nitrifying biological aerated filter at the full-scale Freeport Illinois Wastewater Treatment Plant.; I compared three approaches to modeling of biological activity: the endogenous respiration approach, the death:regeneration approach, and an approach that includes the production of soluble microbial products. I generated a dynamic model of the nitrifying biological aerated system that was based on observation of concentration profiles within the bed and that addressed major phenomena within the system. Co-workers and I used FISH to identify betaproteobacterial ammonia oxidizing bacteria and nitrite oxidizing bacteria in major process streams of the plant on three occasions and attempted to use the information to quantify the biomass composition of these streams. I compared the composition analytical results to model predictions and to general knowledge of the systems to determine the success of quantification.; I found that the three approaches to modeling biological activity differed little in the prediction of ammonium conversion and biomass composition. A key difference was the soluble microbial products approach's ability to predict soluble organic compound concentration. My dynamic model of the nitrifying biological aerated filter process provided reasonably accurate predictions of the effluent ammonia concentration for both routine operation and a system performance test. The model provided insight into the condition limiting process performance and suggests that oxygen availability within the biofilm is the key constraint on performance. The biomass composition quantification accomplished using FISH methods matched anticipated results for the activated sludge system but did not match expectations for the nitrifying biological aerated filter. Small sample size and number probably played a major role in this finding. Additional laboratory work is required to determine the relationships between that which is observed with FISH, actual micro organism mass, and biomass activity quantification used within models of biological treatment systems.