A Modeling Method Study On Bi-cyclic Two-phase (BICT) Biological Process

In the BICT (Bio-Cyclic Two-Phase) biological process, different micro-organisms are intensified in different reactors with two sludge system, so the conflicts between them caused by different metabolism conditions are reduced, thereby the N,P can be removed effectively and steadily. The process is consisted of a biological selector (anaerobic), a main react region (SBR), an independent bio-film reactor and a settling tank. Developing an appropriate and integrative BICT systematic model is propitious to study its identities more deeply and accelerate its engineering process. In this dissertation, it focuses on studying the systematic modeling method.The dissertation's main contents include: select and re-develop the model platform, discuss the modeling method of continuous system and intermittent system in BICT respectively, then connect all the unit models.Firstly, based on reviewing the activated sludge models, settling tank models, and bio-film models, combining with BICT identities, and then select an appropriate model platform. Here, ASM2 is selected as the model platform for the activated sludge system (biological selector and SBR) in BICT, and some re-develop measures are added, such as: neglect chemical phosphorus removal, neglect the dynamic changing of component XTSS during biological reactions, neglect the influence of SALK, and introduce Arrhenius equation to quantify temperature's effects to kinetics parameters. After re-developing, ASM2 consists of 17 react processes and 17 components.Secondly, discuss the continuous system modeling method. The biological selector is regarded as absolute anaerobic condition, and then develop the material balance equations, while neglecting the presence of dissolved oxygen and nitrate. In the settling tank modeling, based on solid flux theory and Takacs model, a one dimension mathematical model for settling tank in BICT is developed. Introducing one-order react kinetics to mathematically describe the reactions in bio-film reactor.Thirdly, discuss the intermittent system modeling method. In BICT process, the biological reactions and control manners of four SBRs are identical. In this dissertation, SBR's one run cycle is divided into"filling & aeration","reaction & return-flow","latter aeration & settling"and"discharging"phases. The run time range of each phase is equal, and there is no biological reactions during settling and discharging.In one run cycle, through analyzing the biological identities and water flow conditions of each phase, an SBR one cycle model is developed. The material balance equations are consisted of dissolved components, dissolved oxygen, particulate components and mixed liquid volume. Based on this, an SBR continuous model is developed via introducing an appropriate time cycle function.Finally, connect all the unit models.Setting different run cycle time ranges of four SBRs to switch one SBR to anther and implement"T/4"time lag during four SBRs. Then, connect the unit models from the following two aspects: conversion of the particulate components'dimensions between biological models and settling models; connection of water flow conditions between continuous systems and intermittent system.