Study On Fenton-like Method Based On Green Nano-iron Combined With Amphoteric Copolymer Sludge Dewatering Agent PADS For Sludge Dewatering

In recent years,with the acceleration of urbanization,sewage discharge and sludge production are increasing year by year.As a by-product of sewage treatment,sludge is a very complex colloid system,which has the characteristics of extremely high water content,high concentration of toxic and harmful substances,great harm,etc.,and its huge volume is not conducive to subsequent transportation,and has potential harm to the environment.How to dewatering sludge more effectively and reduce the difficulty of subsequent treatment has become the focus of attention and research all over the world.In this study,the sludge of a sewage treatment plant in Jinzhong City,Shanxi Province,was used as the target.The sludge dewatering was studied by using self-made amphoteric polymer sludge dewatering agent PADS,Fenton-like oxidation technology based on green nano-iron and Fenton-like method based on green nano-iron combined with PADS.The experimental results are as follows:?1?Polymer sludge dewatering agent PADS was prepared and characterized by FTIR.The results showed that PADS was amphoteric polymer containing cationic group-quaternary ammonium group and anionic group-sulfonic acid group.Plackett-Burman experiment and Box-Behnken experiment were used to optimize the synthetic conditions of PADS.When the mass ratio of monomer?AM?/?DAC+SMAS?was 4.00,the mass fraction of redox initiator was 0.1%,the reaction time was 3 h,the reaction temperature was 40 C,the pH value was6.5,and the stirring speed was 150 r/min,the dehydration efficiency of PADS was the highest.When the dosage of PADS was 7.0 mg/?g DS?,sludge moisture content?Wc?can be reduced from 98.56%to 75.05%,and the sludge specific resistance?SRF?is reduced from 2.98(10¹³m/kg)to 1.23(10¹³m/kg).Compared with the traditional sludge dewatering agent CPAM,the dewatering effect of PADS is obviously better than that of CPAM at the same dosage.It shows that PADS has stronger electric neutralization effect,which can neutralize both positive and negative charged substances in sludge at the same time,and the polymer chain structure makes it have stronger adsorption bridging effect,which can agglomerate sludge particles more quickly and tightly.?2?The Fenton-like method based on green nano-iron was used for sludge dewatering.The effects of H₂O₂ dosage,pH,reaction time,reaction temperature and nano-iron dosage on sludge dewatering were investigated.The results show that the pH range of the method is wide,which is 3⁷,and the sludge dewatering effect is similar.Compared with the traditional Fenton method,the Fenton-like method based on green nano-iron is used for sludge dewatering without pre-acidification to adjust the pH value.Under the initial pH of the sludge of 6.82,the dosage of H₂O₂ is 3.0g/L,the dosage of nano-iron is 1.0g/L,the reaction time is 60min,and the reaction temperature is 20?,the Wc of the sludge is decreased from 98.86%to 70.31%,and the SRF is decreased from2.98(10¹³m/kg)to 0.92(10¹³m/kg).It was observed by scanning electron microscopy?SEM?that the surface structure of the sludge sample treated by this method became irregular and the floc morphology was loose.The SCOD,protein and polysaccharides in the treated sludge supernatant increased by 9.07times,14.93 times and 14.22 times,respectively,compared with those before treatment.It shows that this Fenton-like process can effectively break down the colloidal substance EPS in sludge and the organic substances encapsulated in EPS.?3?Fenton-like method based on green nano-iron is used in combination with PADS for sludge dewatering.The effects of Fenton-like reagents and PADS addition sequence on sludge dewatering were investigated.Studies have shown that:firstly,the sludge treated by Fenton-like oxidation can effectively cleave the organic matter in the EPS and the cell wall of the microorganism to form a water conveyance channel,so that the moisture contained there is released to the outside.Then,PADS is added to aggregate,flocculate and precipitate the finely suspended substances after cracking,thereby significantly improving the sludge dewatering performance and greatly reducing the moisture content of the sludge.After conditioning,Wc and SRF were decreased from 98.43%and 3.14(10¹³m/kg)to 69.86%and 0.85(10¹³ m/kg),respectively.Fenton-like method based on green nano-iron is used in combination with PADS for sludge dewatering.The oxidation of Fenton-like was used to dissolve the organic matter,cell wall and cell membrane wrapped in EPS in sludge without acidification and adjusting sludge pH value.The substances such as protein,polysaccharide and lipid were released into the water phase,which made the bound water inside the cell change into free water and released into the system.With PADS,the smaller negatively charged particles in the boundary can be re-coagulated into large and dense particles suitable for pressure filtration.At the same time,various inorganic suspended particles with positive charge can be aggregated into large particles to form sludge particles with good sedimentation performance,which facilitates subsequent mechanical dewatering.The method can reduce the cost of sludge dewatering and improve the economic benefits of sewage treatment plants.