Process Control Mechanism Of Multi-class Fertilizer Draw Forward Osmosis Membrane Wastewater Treatment Process And Application Of Effluent In Irrigation

Forward osmosis（FO）is a separation process membrane technology driven by osmotic,the osmotic pressure gradient through the semipermeable membrane would drive water from the feed solution（low osmotic pressure）side to the draw solution（high osmotic pressure）side,due to the low pressure needed in the process,FO membrane has several advantages of low energy consumption,low fouling tendency,easy to clean,higher water recovery rate and other potential advantages.Fertilizer Draw Forward Osmosis（FDFO）is a process for treating contaminated water by using fertilizer as draw solution for forward osmosis membrane separation process.The novelty based on FO technology lies in the diluted draw solution.Because this type draw solution can be directly used for irrigation without the separation and recovery process of draw solution,thereby it can save energy.In addition,fertilizers are widely used in agriculture which is ideal for forward osmotic draw solution.Fertilizer Draw Forward Osmosis Membrane Reactor（FDFOMBR）is a new type of water treatment technology that combines membrane separation technology and bioreactor.Compared with traditional activated sludge process,it has a new water treatment technology,it has good effluent quality,small equipment footprint,high concentration of activated sludge,low sludge yield and higher automatic control.It is one of the most promising new technologies for wastewater treatment.However,FDFO and FDOMBR still face challenges in practical applications,such as the optimization of the draw solution,the optimization of the process parameters,the reverse salt solute and the accumulation of salt in the reactor.These challenges will result in loss of water flux,inactivation of microorganisms in the bioreactor,and reduction in effluent quality.In this paper,different fertilizers were used as the draw solution for the forward osmosis process for treating domestic wastewater and fermentation leachate with irrigation purpose.In order to alleviate the accumulation of salt in the reactor,the combined MF process and degradable organic fertilizer draw solution were used to investigate the effect on the performance of OMBR.The main content and conclusions of this paper are as follows:1.Application of FDFO process in green wall irrigation and study of its membrane fouling.This study explored the application possibilities of forward osmosis membrane technology to irrigate outdoor green wall.The experimental performance,membrane cleaning strategy and membrane fouling of two different membranes of CTA and TFC were compared.In this process,membrane bioreactor effluent is used as feed solution,liquid commercial fertilizer as draw solution.The experimental results show that the TFC membrane is suitable for the short-time concentration of MBR effluent.The water flux is 15.04 L·m^-2h^-1,which can achieve 38%water recovery.While the CTA membrane is more suitable for concentrating the MBR effluent for a long time and TFC is more prone to membrane fouling than CTA.In the membrane cleaning strategy study,it was found that the water flux recovery rate of the CTA membrane was higher than the TFC membrane.Through the surface FTIR and electron microscopy analysis of the original membrane,the contaminated membrane and the cleaned membrane,it was found that the main component of the film contamination was organic fouling,and most of the membrane fouling could be removed by membrane cleaning.2.Application of FDFO process in concentrating vegetable leachate and study of its membrane fouling.In this study,FDFO was used to concentrate vegetable leachate.The operating parameters and the fouling mechanism of simulated vegetable leachate was investigated.The optimized process experiment results show that（NH₄）₂SO₄ has a higher water flux(water flux of 7.31 L·m^-2h^-1 at 1 mol·L^-1)and a low reverse salt permeation rate(0.102 g·L^-1).it is found that organic matter and calcium may be potentially fouling compounds by the analysis of FTIR and XPS.It is found that anthocyanin to be the main cause of red fouling on the surface of the membrane and decrease in water flux.Furthermore,calcium ions can also form more serious pollution.3.Mitigation of salt accumulation in FDFOMBR by combing MF process.In this study,MF process was introduced to alleviate the accumulation of salt in the bioreactor and improve the performance.Operating parameters include the type of draw,the concentration of the draw,the flow rate of the draw solution,and the MF water flux were investigated.The optimal conditions are as follows:The most suitable draw solution is ammonium sulfate,the concentration is 1 mg·L^-1,the flow rate of the draw solution is 200 m L·min^-1,and the MF water flux is 10 L·m^-2h^-1;The addition of the MF membrane process was found that can effectively control the salinity in FDFOMBR,increase the water flux of FO and the activity of microbial degradation of organic matter.4.Mitigation of salt accumulation in FDFOMBR by using organic ionized fertilizer as draw solution.In this study,degradable acetate-based organic fertilizers were selected as the draw solution for the domestic sewage treatment with forward osmosis bioreactor.The FDFO and FDFOMBR performance of ammonium acetate（NH₄C₂H₃O₂）,sodium acetate（Na C₂H₃O₂）and potassium acetate（KC₂H₃O₂）were compared to ammonium sulfate（NH₄）₂SO₄ sodium chloride（Na Cl）and potassium chloride（KCl）corresponding inorganic draw solution.In FDFO experiments,when ammonium acetate,sodium acetate and potassium acetate organic ion solution is used as draw solution,the water flux value is slightly lower than the ammonium sulfate,sodium chloride and potassium chloride.In the FDFOMBR process,the dilution ratio of（NH₄）₂SO₄ as the draw solution in FDFOMBR is the highest.The experimental results show that the organic ion draw solution can alleviate the salt accumulation in the reactor.But it is more prone to cause the membrane fouling.