Integration Of Reverse Osmosis And Fenton Process For The Treatment Of Organophosphorus Wastewater

In recent years, reverse osmosis(RO) is widely applied in the field of wastewater treatment. However, it seems that the treatment of waste with tetrakis hydroxymethyl phosphonium salt(THP) are rarely reported. Due to hight content of chemical oxygen demand(COD), biotoxicity and salinity, it can be hardly treated by conventional biochemical technology. In this thesis, RO-Fenton method was firstly adopted for the recovery of THP and qualified wastewater discharge. The main contents included:①the removal of phosphorus in the waste of tetrakis(hydroxymethyl)phosphonium sulfate(THPS) by ion exchange resin;(2)the application of reverse osmosis in the separation of phosphorus in THP waste;③the degradation of COD in simulated wastewater and RO permeat using Fenton reagent. The results were summarized as follows:(1)Strong-acid cation exchange resin was selected as the study subject due to higher static adsorption capacity and adsorption rate. Dynamic experiments showed that at room temperature,9.7g resin was acceptable for500mL THPS waste at flow rate15mL/min and it was regenerated by250mL1mol/L HCl at5mL/min. Under studied conditons, dynamic adsorption capacity of THPS was up to10.73mg/g, the desorption efficiency of resin came to89.73%and long time use of resin had a negative effect on the regeneration process. Furthermore, the effluent were not in line with emission standards, in which average total phosphorus(TP), HCHO and COD were28.43mg/L,2481.5mg/L and992.3mg/L, respectively.(2)The performance of RO system to reuse and remove THP from the waste was studied. With a feed pressure of70bar and a flow of3m3/h, the average rejections of THPS and tetrakis(hydroxymethyl)phosphonium chloride(THPC) were98.7%and97.6%, which resulted in total phosphorus in the permeat lower than10mg/L for both THPS and THPC waste. As for RO concentrate where THPS and THPC were highly enriched, it was found that THPS and THPC were11.6,7.7times the concentration of the feed water, which meet the requirement of reclamation. However, the permeat was still rich in HCHO and COD, and needed further treatment.(3)Simulated wastewater and RO permeat containing HCHO was degraded by classic Fenton’s oxidation. For the former, the optimal condition of Fenton system included initial pH2.5, reaction time30min, H2O2dose0.7mL and H2O2/Fe2+molar ratio90. Within above experimental condition, HCHO removal rate reached to90.9%.Without pH regulation, working with a molar ratio H2O2/Fe2+=20,1.4mL H2O2dose and12h reaction time at ambient temperature led the permeat to a HCHO reduction of94.7%and COD conversion of87.6%. After oxidation, the content of HCHO and COD were102.5mg/L and474.6mg/L, which indicated that Fenton’s reagent is a feasible way to partially treat RO permeat to achieve a significant decrease of COD.