| Sewage treatment processes are complex dynamic non-linear systems,many of which are difficult to quantify,resulting in the experience was tend to be relied on during the actual opeations.The observation of sludge morphology,especially during the sedimentation process,is one of the important parts for the actual sewage treatment.To some extent,the change of floc morphology of activated sludge can reflect the operation state of sewage treatment plant,but there is no effective method of system.And the observation,analysis and strategies based on the morphology differ from each other,with great uncertainty.Therefore,how to quantify and systematize the observation of sludge morphology is the key to ensure the effective operation on a large number of small-scale sewage treatment plants in our country,most of which were under the limited condition of insufficient facilities.In view of the current situation that sewage treatment plants rely on experience to operate in China,on the basis of traditional morphological observation,the mechanism and quantitative interpretation of empirical methods are carried out by using information technology.In this paper,the image analysis technology is used to propose the macro-scale void fraction index to characterize the research of activated sludge and biological activity,so as to realize the simple and rapid evaluation of sludge properties and biological activity.Furthermore,it is promising to lay foundation of fast and low-cost detection technology for the sludge performance.Based on the image morphological characteristics of sludge settling process,this study focused on the internal relations between macro-scale void fraction and micro morphology,as well as settling performance,flocculation and adsorption performance,settling compression performance and new parameters of biological activity,and the main results were as follows:(1)There is a certain correlation between the macro-scale void fraction and the flocculation performance of sludge at the initial stage of sedimentation:the more the LB-EPS is,the worse the relative hydrophobicity is,and the worse the sedimentation performance is,and the smaller the flocs are formed in the sedimentation process,which suggested the larger the initial macro-scale void fraction.(2)At the initial stage of sedimentation,the macro-scale void fraction is affected by the micro structure of flocs:for sludge with small internal porosity,the flocs formed in the sedimentation process were small,which leads to large initial macro-scale void fraction,small OUR_q/OUR_t and poor adsorption performance in terms of microbial respiratory activity.(3)The macro-scale void fraction of 30 min-sedimentation is related to the sludge settling compression performance.The larger the porosity is,the weaker the effect of compression settlement is.(4)The conclusions above have been applied in AAO process and CASS process.In the process of AAO and CASS,the initial macro-scale void fraction is negatively related to the ratio of OUR_q to OUR_t(OUR_q/OUR_t),which is related to sludge structure and adsorption performance.The smaller the value of OUR_q/OUR_t,the closer the sludge structure is,and the worse the adsorption performance is.When the initial macro-scale void fraction is larger,the flocculation performance of sludge is poorer,and the flocs formed are smaller,and the porosity inside the flocs is smaller,and the sludge structure is tight,and the adsorption performance is poorer,and the value of OUR_q/OUR_t is smaller.There is a positive correlation between the 30 min macro-scale void fraction and SVI,and there is a high correlation.The larger the 30 min macro-scale void fraction is,the worse the settlement performance is.There was a positive correlation between the 30 min macro-scale fraction and OUR_c/OUR_t that the stronger the denitrification became in the sludge system,the larger the 30min macro-scale void fraction was observed. |
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