Research On The Effectiveness And Stability Of Potassium Ferrate With Straw Fiber Reinforced Solidification Of Sludge

Sludge as a byproduct of wastewater treatment is characterized by high yield,high moisture content,and high organic matter content,which can easily lead to secondary pollution if treated and disposed of improperly.Sludge solidification/stabilization treatment is one of the technologies for the treatment and disposal of sludge that meets the current economic and technological level in China.A key factor hindering the cement hydration reaction is the high organic content of the sludge,which weakens the solidification effect and affects the long-term stability of the solidified sludge,which is a key issue restricting the application of this technique.With this in mind,this study focuses on the problems in the existing sludge solidification/stabilization technology and conducts a study on the enhanced effect of solidified sludge and the stability of solidified sludge by potassium ferrate in cooperation with straw fiber,with sludge from the municipal sewage treatment plant as the research object.Potassium ferrate synergetic skeleton material was studied to enhance sludge solidification.The results showed that a minimum admixture of cement,potassium ferrate,and straw fiber was found to exist in the single-factor test,which was 10%,5%,and 5%,respectively.When it is less than this value,the solidification effect is insignificant,and when it is greater than this value,the unconfined compressive strength of the solidified sludge increases with the increase of the admixture amount.The orthogonal test found that potassium ferrate and straw fiber had significant effects on the unconfined compressive strength and were positively correlated with the unconfined compressive strength,with straw fiber having the greatest effect and cement having no significant effect on the unconfined compressive strength.The ideal optimal condition is that the higher the amount of potassium ferrate and straw fiber,the better,and the amount of cement to ensure that the cementing effect is appropriate.Considering the actual landfill requirements,the evaluation indexes such as moisture content,bulking ratio,and cost were added based on the unconfined compressive strength,and the final suitable ratio was further optimized by linear weighting,and the result was 20% cement,10% potassium ferrate and 5% straw fiber,and the unconfined compressive strength was126.87 k Pa,which far exceeded the sludge landfill strength requirements(50 k Pa).A comparison of the solidification effect of Straw fiber and inorganic skeleton materials found: the single-skeleton material solidification experiment shows that slag and fly ash have better effects while shell powder and straw fiber have similar effects.However,in each skeleton material synergistic potassium ferrate solidification,straw fiber is significantly better than inorganic skeleton material.Combined with strength,moisture content,capacity increase ratio and cost,straw fiber composite index is maximum.The mechanism of enhanced sludge solidification effect by potassium ferrate in synergistic with straw fiber was investigated.The results show that potassium ferrate can oxidatively break the organic matter structure of sludge,and increase the content of free water to 4.95% and reduce the content of bound water to 78.21%,which is conducive to a more adequate hydration reaction between cement and low potential energy-free water during the solidification process.In addition,during the oxidation process,it also converts organic matter macromolecules into small molecules of organic matter and inorganic salts,and the small molecules of organic matter are adsorbed by straw fibers during the curing process to reduce the interference of the hydration reaction and generate more gismondine crystals;inorganic salts also form hemihydrate gypsum crystals with the hydration products.Moreover,the straw fiber itself has tensile and flexural properties,forming an intricate skeleton support system in the cured sludge,which plays the role of anchoring and reinforcement to enhance the strength of the final solidified sludge.The stability and physicochemical properties of solidified sludge were studied under simulated rainwater-leaching landfill conditions.The results showed that the solidified sludge was almost unaffected by rainwater leaching,and its unconfined compressive strength,moisture content,and organic matter were very stable and remained within the appropriate range.In addition,the internal biochemical environment of the solidified sludge was changed,and the p H of the leachate also showed strong alkalinity,which seriously inhibited the physiological activity of anaerobic bacteria and prevented the anaerobic reaction from proceeding,and the landfill gas production was zero.Therefore,this sludge solidification and landfill disposal method is sufficiently stable and meets the needs of China’s carbon emission reduction policy.