Abstract:
Abstract: With the large scale of application and development in biogas project, the effective way to dispose the biogas slurry and other anaerobic fermentation residues becomes the bottleneck in biogas anaerobic fermentation technology development. To optimize the reaction conditions of osmosis technology for nitrogen removal, and with a consideration of ammonia nitrogen removal efficiency as the response value, Plackett-Burman test was used to determine the main factors from four affecting factors and the maximum ammonia nitrogen removal rate was obtained by using the steepest ascent test. Based on this, the Box-Behnken response surface method was used to optimize the significant factors. The results of Plackett-Burman test showed that the main factors affecting the removal rate of ammonia nitrogen were: the operating pressure, the recovery rate, and the pH value. When the steepest ascent test was closer to the optimal response region, we obtained the operating pressure of 5.4 MPa, the pH value of 7.5, the recovery rate of 75%. The optimization results can be known by the Box-Behnken response surface method. The impact of these three factors on ammonia removal efficiency was the operating pressure > the recovery rate>pH. The interaction of the operating pressure and the recovery rate, pH and the recovery rate were extremely remarkable.. The best experimental conditions for the maximum removal rate of ammonia (96.46%) were: the operating pressure of 5.53 MPa, the pH value of 7.70, and the recovery rate of 76.02%. Considering the controllability of the actual operation, the optimal test conditions were adjusted as: the operating pressure of 5.50 MPa, the recovery rate of 76%, the pH value of 7.70. Under such conditions, the mean value of ammonia nitrogen removal rate was 96.13% from three tests. We also used the quadratic regression equation to model the experimental results. The model output was very close to the test values, the error was only 3.43%. This showed that the quadratic regression equation can be used to reflect the effects of the selected factors, and the establishment of the model and the actual situation were quite fit. After obtaining optimal reaction conditions, we then implemented those conditions in disc-tube reverse osmosis membrane module system. The system has a unique open channel and special scientific hydraulic design, from which the turbulent state of the biogas slurry can make pollutants generated slowly effectively, and prolong the reverse osmosis membrane using time. The results showed that the optimization of the operating pressure, the pH value, the recovery rate improved the removal efficiency of ammonia nitrogen, and also provided an effective way to reduce membrane fouling. In all, by using response surface analysis method for ammonia nitrogen removal from biogas slurry in osmosis technology, we obtained optimal ammonia nitrogen removal rate of process parameters, and those parameters were proved to work in the operational reverse osmotic pressure systems. Our study provided a theoretical basis for in-depth understanding. The research will have a good application to biogas slurry ammonia reduction and enrichment technology.