Optimization of sludge conditioning and dewatering continues to be a challenge due to continuous changes in sludge characteristics and solids concentration during operation. For this reason, dewatering of wastewater sludge has received considerable research attention even in order to reduce the cost of sludge treatment and final disposal. Ideally, polymer dose should be checked and optimized on a real-time basis, but the majority of treatment plants manually adjust the polymer dose by checking cake solids or performing jar tests when they see necessary. This usually leads to overdoses of polymer, typically by 30-40% (Ormeci and DiMassimo, 2016), which not only increases the polymer cost for the plant but also decreases filtrate quality due to presence of free polymer material. A wetter cake could increase sludge handling and disposal costs substantially. Measuring polymer concentration during conditioning and dewatering operation would provide information on whether too much or too little polymer is added to sludge, and would also provide a tool to optimize and minimize the polymer dose on real-time basis maintaining the optimum related to the dewatering performance. The most effective method for optimization of sludge dewatering would be to measure the polymer concentration directly. Current dewatering optimization systems on the market rely on indirect parameters such as solids concentration of incoming sludge or turbidity of the effluent, which are not effective in capturing important sludge characteristics and predicting dewatering performance. Furthermore, in addition to methods based on organic carbon content, chemical and turbidimetric methods were employed to quantify aqueous polyacrylamide concentration; these analytical approaches normally rely on chromatography and mass spectrometry, and often require the addition of various reagents (Ormeci and DiMassimo, 2016; Lents, Sojka and Foerster, 1996). Even though there is a wide range of procedures available for measurement and characterization of polymers, none of these is suitable for in-line and real-time applications on industrial environment. Over the last few years, a new spectrophotometry based method was developed to measure the residual polymer concentration in filtrate and centrate after dewatering (Gibbons and Ormeci, 2013; Al Momani and Ormeci, 2014). It was shown that there is a strong linear relationship between polymer concentration and sample absorbance at 190 nm, and the polymer concentration can be determined by measuring the absorbance of a sample and using a calibration curve. This study is based on the working principle of the new advanced polymer optimisation system EnvistaTM Vis; it consists of a spectrophotometer that measures the absorbance of light emitted at 191 nm and automatically identifies and sets the optimum polymer dose for sludge dewatering.
ENVISTATM VIS: UN NUOVO SISTEMA BASATO SULL’ASSORBANZA IN LINEA E IN TEMPO REALE FINALIZZATO ALL’OTTIMIZZAZIONE DEL DOSAGGIO DI POLIMERI NEL PROCESSO DI DISIDRATAZIONE DEL FANGO
ENVISTATM VIS: A NEW IN-LINE AND REAL-TIME ABSORBANCE BASED SYSTEM FOR POLYMER OPTIMISATION IN SLUDGE DEWATERING
SACCHI, STEFANIA
2015/2016
Abstract
Optimization of sludge conditioning and dewatering continues to be a challenge due to continuous changes in sludge characteristics and solids concentration during operation. For this reason, dewatering of wastewater sludge has received considerable research attention even in order to reduce the cost of sludge treatment and final disposal. Ideally, polymer dose should be checked and optimized on a real-time basis, but the majority of treatment plants manually adjust the polymer dose by checking cake solids or performing jar tests when they see necessary. This usually leads to overdoses of polymer, typically by 30-40% (Ormeci and DiMassimo, 2016), which not only increases the polymer cost for the plant but also decreases filtrate quality due to presence of free polymer material. A wetter cake could increase sludge handling and disposal costs substantially. Measuring polymer concentration during conditioning and dewatering operation would provide information on whether too much or too little polymer is added to sludge, and would also provide a tool to optimize and minimize the polymer dose on real-time basis maintaining the optimum related to the dewatering performance. The most effective method for optimization of sludge dewatering would be to measure the polymer concentration directly. Current dewatering optimization systems on the market rely on indirect parameters such as solids concentration of incoming sludge or turbidity of the effluent, which are not effective in capturing important sludge characteristics and predicting dewatering performance. Furthermore, in addition to methods based on organic carbon content, chemical and turbidimetric methods were employed to quantify aqueous polyacrylamide concentration; these analytical approaches normally rely on chromatography and mass spectrometry, and often require the addition of various reagents (Ormeci and DiMassimo, 2016; Lents, Sojka and Foerster, 1996). Even though there is a wide range of procedures available for measurement and characterization of polymers, none of these is suitable for in-line and real-time applications on industrial environment. Over the last few years, a new spectrophotometry based method was developed to measure the residual polymer concentration in filtrate and centrate after dewatering (Gibbons and Ormeci, 2013; Al Momani and Ormeci, 2014). It was shown that there is a strong linear relationship between polymer concentration and sample absorbance at 190 nm, and the polymer concentration can be determined by measuring the absorbance of a sample and using a calibration curve. This study is based on the working principle of the new advanced polymer optimisation system EnvistaTM Vis; it consists of a spectrophotometer that measures the absorbance of light emitted at 191 nm and automatically identifies and sets the optimum polymer dose for sludge dewatering.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/22413