| Nowadays,traditional methods for wastewater quality monitoring suffer from low efficiency,and issues of secondary pollution.Most commonly used online sensors have drawbacks in data drift and physical fouling.A novel UV-visible spectroscopy-based online monitoring spectrometer was developed to address these challenges in wastewater monitoring.Experiments were carried out to investigate its performance in monitoring suspended solids in wastewater.Meanwhile,with the acceleration of industrialization,effective monitoring and treatment of refractory organic compounds has become an urgent problem in the field of wastewater treatment.Against this background,a prediction model for refractory organic compounds was built based on spectral processing algorithms and chemometrics.The pilot experiment of ozone and electrochemical advanced oxidation process to oxidize refractory organic compounds was carried out.The application potential of UV-visible spectroscopy in the control of advanced oxidation processes was explored.The main research content and results are as follows:(1)This study investigated the monitoring performance of a novel UV-visible online spectrometer under the influence of different types and concentrations of suspended solids.It was found that the absorbance shift caused by montmorillonite was proportional to the absorbance value when unaffected,while activated sludge caused a slight decrease in absorbance in the UV region with no significant regularity.Based on data disturbance and data loss as evaluation criteria,the maximum allowable suspended solid concentrations for monitoring at optical path lengths of 10 cm,5 cm,3 cm,and 1 cm were determined as 102 mg/L,134 mg/L,231 mg/L,and 550 mg/L,respectively.A water quality index prediction model with turbidity compensation capability was established based on actual wastewater data from a wastewater treatment plant,with root mean square errors of prediction(RMSEP)of 0.947 for nitrate nitrogen and 3.217 for chemical oxygen demand(COD)models.The results showed that the spectrometer combined with chemometric methods could achieve online water quality monitoring in the presence of suspended solids,but the appropriate optical path length should be selected based on the application environment and suspended solid concentration.(2)This study investigated the ability and detection limits of UV-visible spectroscopy for online monitoring of refractory organic compound concentrations.The minimum detection limits of refractory organic compounds were analyzed using the spectrometer at optical path lengths of 10 cm,5 cm,3 cm,1 cm,and 0.5 mm,with values of 3.1 μg/L,18.4 μg/L,43.7 μg/L,75.4 μg/L,and 464.7 μg/L,respectively.The decrease in detection limit slowed down with increasing optical path length.The detection limit for recalcitrant organic compounds was found to be 94 μg/L by monitoring actual wastewater(with a 1cm optical path length).Furthermore,this study established prediction models using feature extraction and optimal preprocessing algorithms.The model exhibited good predictive ability for the concentrations of ciprofloxacin,tetracycline,and chloramphenicol in a mixture sample with overlapping absorption peaks,with the lowest RMSEP of 0.84635 achieved for tetracycline concentration.These research results demonstrate that UV-visible spectroscopy,combined with feature extraction,can effectively solve the concentration prediction problem under spectral overlap and achieve detection limits suitable for application in real wastewater.(3)This study investigated the potential correlation between UV-visible spectroscopic changes and reaction progress during advanced oxidation processes.In the electro-Fenton oxidation process,the absorbance at 240-260 nm generated by the spectrometer exhibited a strong correlation with COD concentration,allowing for process control through COD indication.It was found that the absorbance spectra of tetracycline,ciprofloxacin,hydrochlorothiazide,and diphenylamine changed during the oxidation process and reflected partial changes in chemical structure by monitoring the ozone oxidation process of five organic compounds with benzene rings(tetracycline,ciprofloxacin,chloramphenicol,hydrochlorothiazide,and diphenylamine),and providing real-time data for oxidation process control.These results indicate that the spectrometer has the capability for process control in advanced oxidation processes.This study investigated the influencing mechanisms of suspended solids and optical path length on a novel UV-visible online sensor.A prediction model for refractory organic compounds based on UV-visible spectroscopy was constructed to support intelligent control of the treatment process.An online monitoring method using UV-visible spectroscopy for process control in advanced oxidation processes was established,thereby reducing energy consumption. |
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