Chemi-thermo-mechanical pulping(CTMP)wastewater has high chemical oxygen demand(COD),which inhibits the activity of microorganisms during biological oxidations.Conventional wastewater treatment technologies such as dissolved air flotation,coagulation,and biological treatment,are insufficient to treat the CTMP wastewater to meet the environmental requirements.There remains a need for advanced wastewater treatment technologies,which can be integrated into existing wastewater treatment processes to improve the end-of-pipe water quality.In this study,a heterogeneous electrochemical oxidation process was developed to treat chemi-thermo-mechanical pulp mill wastewater.The Ti substrate anodes were prepared by thermal decomposition and electro-deposition,and characterized by SEM and Tafel curve.The impacts of electrode modification,flowrate,current density,and aeration on the process efficiency were investigated.COD and color density were used to evaluate the removal efficiency of organic pollutants.Results show that the Ti/SnO_(2)+Sb_(2)O_(3)+MnO_(2)/PbO_(2) electrode exhibited the best performance in terms of COD and color removal efficiency.SEM observation revealed that the electrode surface was smooth and compact,with numerous uniform micro pores of which the inner walls were covered with tiny crystals.Under the studied conditions,color removal reached 90%,while COD removal was about 60%.
In this paper, the peak-to-average power ratio(PAPR) of orthogonal frequency division multiplexing(OFDM) signal is reduced by combining the discrete cosine transform(DCT) with clipping in optical intensity-modulated direct-detection(IM/DD) OFDM systems. First, the data are transformed into new modified data by DCT. Second, the proposed scheme utilizes the clipping technique to further reduce the PAPR of OFDM signal. We experimentally demonstrate that the optical OFDM transmission system with this proposed scheme can achieve significant performance improvement in terms of PAPR and bit error rate(BER) compared with the original optical OFDM systems.
