Probing Hydraulic Mixing Conditions Of Activated Sludge Based On HSV Color Space

The deterioration of hydraulic mixing conditions was often caused by uneven mixing,poorer pool structure and short-circuiting in wastewater treatment plants（WWTPs）,however,due to an effective method has not been established for monitoring the change of hydraulic mixing conditions,limited the practical application in general operation of WWTPs.On the other hand,along with the popularity of image acquisition devices,especially the extensive use of smart phone devices,the cost of image information acquisition has dropped dramatically,so the image color information has a good application prospect in WWTPs.On the basis,the research subject focus on activated sludge and anaerobic ammonia oxidation（Anammox）sludge under four different operating conditions,exploring and summarizing a method using HSV color space for monitoring the change of hydraulic mixing condition,which validates in two different activated sludge systems of actual operation of WWTPs,and the application could greatly cut down the economic and time cost,providing a guidance for the WWTPs.The following results were obtained:（1）Based on four different operating conditions of the activated sludge HSV color space analysis,the change of Hue indicates that the natue of sludge has changed,meanwhile the increase of standard deviation of Hue（σ_H）indicates the sludge mixing conditions gradually deteriorated.Value S represents the color saturation,and the change of S is related to the apparent color of sludge,when activated sludge system deteriorated,it can be found S gradually decreased,which plays a minor role in the characterization of sludge mixing condition.And the derivative index CV_H/S of HSV contains H and S color information,the smaller CV_H/S indicates better mixing conditions.At the same time,it was found that the quasi-endogenous respiration rate OUR_q increased gradually when the mixed conditions of activated sludge deteriorated.Therefore,the combination of OUR_q and CV_H/S can be used to characterize the hydraulic mixing of activated sludge system from two aspects of sludge color information and respiration rate.（2）In two different processes of the actual operation of WWTP,the Oxidation Ditch（OD）is classified as the fully mixed process,and the properties of activated sludge shows similar in reactor,resulting a small difference CV_H/S.MAAO process is classified as plug flow process,different mixing conditions of activated sludge in different reactor location lead to sludge properties varied,calculating a large CV_H/S difference,which shows CV_H/Scan be applied to actual operation of WWTP for enhancing the ability of monitoring hydraulic mixing conditions.（3）Anammox sludge color during the experiment from black inoculation cultured to the red in the end,H decreases gradually,S and CV_H/S fluctuated.Moreover,it also noticed CV_H/S is more sensitive to the change of sludge system than S,especially with the intermittent increase of influent and effluent water load,finding that CV_H/S could be better probing the change of hydraulic load.Therefore,CV_H/S can be used to characterize the whole startup process of anammox.（4）From the analysis of 16S rRNA sequencing results of microorganisms,the total number of microbial communities in anammox sludge is increasing and the diversity is decreasing.And the dominant microflora gradually converted from denitrifying bacteria Ottowia at inoculation to anammox Candidatus Anammoxoglobus in the end,the function of anammox has been strengthened and occupied a dominant in the activited sludge system.