| Sludge digester contains a large amount of nitrogen and phosphorus,if it is directly returned to the biological treatment unit,it is easy to cause the sewage treatment plant load is too high,affecting the effluent quality.As a kind of wastewater treatment,it wastes a large amount of nitrogen and phosphorus resources,which does not meet the requirements of sustainable development of today's society.In this paper,AnFMBR technology is proposed to be applied in the treatment process of sludge digester,and through the addition of biomass semi-coke,ultrasonic sludge reflux to achieve good treatment effect,low membrane pollution.In addition,after the sludge is treated by ultrasonic wave,the supernatant contains a large amount of nitrogen and phosphorus.In this experiment,the supernatant is treated by the combined method of stripping and magnesium ammonium phosphate precipitation,so as to recover a large amount of nitrogen and phosphorus.Different modified biomass semi-cokes were prepared and their adsorption properties and effects on anaerobic treatment and sludge properties were studied.Results after the modification of the semi-coke,the surface functional groups became richer,and the hydrophilic and hydrophobic properties changed obviously.The stronger the hydrophilic semi-coke is,the stronger the adsorption capacity of COD and phosphate is,which indicates that in general,the adsorption capacity of substances is proportional to their hydrophilicity and hydrophobicity.The unmodified semi-coke has the strongest adsorption capacity of ammonia nitrogen,which is because the unmodified semi-coke contains a lot of inorganic salts and can be cation exchange adsorption with ammonia nitrogen.The addition of semi-coke has a positive effect on pollutant removal,and the hydrophilic semi-coke has the best effect on pollutant removal.The effect of different concentration of semi-coke on anaerobic treatment is also different.Under MLSS: semi-coke mass ratio of 2:1,the pollutant removal effect is the best.It is found that the effects of different concentrations and different kinds of semi-coke addition on sludge properties are different.The sludge viscosity is the minimum when the sludge concentration is 1:1.When the addition ratio is 1:2,the sludge Zeta potential is the minimum,and the more the semi-coke addition,the larger the sludge particle size and the higher the sludge concentration.It was found that the addition of hydrophilic modified semi-coke was most beneficial to the reduction of sludge viscosity,the increase of sludge particle size and the increase of sludge concentration.However,the unmodified semi-coke is most beneficial to the reduction of Zeta potential of sludge.The effects of different ultrasonic treatment conditions and semi-coke addition on sludge ultrasound were studied.The results showed that the release rate of ammonia nitrogen,phosphate and COD in sludge was increased with the increase of ultrasonic power and ultrasonic time.Different kinds of biomass semi-coke had different influences on the release of pollutants,both positive and negative.In general,when the sludge concentration is 1:1,COD and ammonia nitrogen have the best dissolution effect;when the sludge concentration is 2:1,phosphate has the best dissolution effect.Adding hydrophilic modified biomass semi-coke had the best effect on the dissolution of COD and phosphate,while adding unmodified biomass semi-coke was most beneficial to the release of ammonia nitrogen.In the study of nitrogen and phosphorus recovery system,it was found that the blowing rate of ammonia nitrogen was proportional to pH,blowing time and temperature.In the precipitation process of magnesium ammonium phosphate,the best removal effect is achieved when the pH is controlled at 9.0.The removal rate of phosphate increased with the increase of the proportion of ammonia nitrogen,but when P:N exceeded 1:1.2,its value did not increase significantly.When nitrogen and phosphorus were recovered from the water by blow and support combined MAP precipitation method and simple MAP precipitation method,it was found that blow and support combined MAP precipitation method had better recovery efficiency for ammonia nitrogen.When the performance of sludge digester was treated by AnFMBR reactor,it was found that the addition of semi-coke was beneficial to the removal of COD,and the total removal rate of COD increased from 68.09% to 71.67%,and the removal rate of COD was mainly reflected in the film interception.The addition of semi-coke has no effect on the removal of ammonia nitrogen and phosphate.The removal rates of COD,ammonia nitrogen and phosphate were significantly increased after the ultrasonic sludge reflux operation.The removal rates of COD,ammonia nitrogen and phosphate in AnFMBR1 reactor were 87.58%,43.52% and 49.28%,respectively.The removal rates of COD,ammonia nitrogen and phosphate in AnFMBR2 reactor were 89.41%,49.28% and 54.98%,respectively.Semi-focus also plays an active role in ultrasonic reflux.In the whole operation period,the degree of membrane pollution from heavy to light under four operating conditions is: > semi-coke > ultrasound and > ultrasound plus semi-coke.The addition of semi-coke is beneficial to reduce membrane pollution,and the ultrasonic sludge reflux operation is beneficial to reduce membrane pollution.The study on the sludge and pollutant properties of the two reactors shows that the reasons of reducing membrane pollution are different.Semi-coke addition is mainly because it can reduce the SMP,EPS and sludge viscosity in the reactor,and is beneficial to improve the structure of mud cake layer so as to reduce membrane pollution.Ultrasonic sludge reflux operation is mainly to reduce membrane pollution by reducing EPS and viscosity in the reactor and improving hydraulic performance of the reactor.Zeta potential,sludge concentration and sludge particle size are not the main factors affecting membrane pollution in this study. |
PDF Full Text Request