Jacobs Journal of Civil Engineering

Effect of Organic Loading and DO on Stability of Hypersaline Aerobic Granular Sludge

* Miaomiao Dong
Department Of Civil Engineering, Chongqing Jiaotong University, China

*Corresponding Author:
Miaomiao Dong
Department Of Civil Engineering, Chongqing Jiaotong University, China
Email:dmm201309@sina.com

Published on: 2015-08-15

Abstract

In order to investigate the effect of organic loading and dissolved oxygen (DO) on the characteristics of hypersaline aerobic granular sludge in some sequencing batch reactors (SBR), the indicators of sludge were analyzed such as the sludge volume index (SVI), minimal sedimentation rate, dehydrogenase activity, extracellular polymeric substances (EPS) component and size distribution of granule. Results indicate that the effect of organic loading and DO on the stability of aerobic granular sludge is significant. The organic loading which is over low or over high does not go against the stability of granular sludge. Over high organic loading can inhibit the growth of granular sludge and decrease the dehydrogenase activity and the content of extracellular proteins (PN), which cause granular sludge disintegrate and worse stability of granular sludge. The content of EPS in granular sludge achieves maximum under the organic loading of 5.4 kgCOD•(m3•d)-1, and the EPS is given priority to with extracellular proteins, resulting in the larger of average particle size, uniform of size distribution, thus the granular sludge displays a good stability. Over low DO can easily trigger filamentous bacteria breeding, and which can cause that granular sludge is unstable, increasing DO concentration can promote the growth of granular sludge, and the size distribution can be more concentrated, but over high DO can affect the stability of the system, because providing over high hydraulic shear force can lead to granular sludge disintegrating. When the reactor is controlled under DO of 6mg•L-1, the EPS is mainly with extracellular polysaccharide.

Keywords

hypersaline; aerobic granular sludge; stability; organic loading; dissolved oxygen

Introduction

Aerobic granular sludge is a special kind of biofilm, which is formed by cell self-immobilization in aerobic conditions. It shows good settle ability, which indicates that using aerobic granular sludge can reduce the volume of reactor, shorten the process operation cycle and improve the processing efficiency, especially in sequencing batch reactor. It has high biomass, so the process has higher capacity in resistance to shock loading and can bear higher organic loading. It is regarded as the ideal subject to realize the integrated treatment of biological nutrient in wastewater for its abundant microbe phase and diversified forms in metabolism [1].