Study On Calcification Control Of Anaerobic Granular Sludge In Papermaking Wastewater

The use of IC anaerobic reactor to treat papermaking wastewater has the advantages of high volume load,good treatment effect and small footprint.However,in recent years,the government advocates water conservation and changes in papermaking raw materials,which has caused serious calcification of anaerobic granular sludge,affecting the anaerobic biological treatment effect of papermaking wastewater,and not conduciving to the discharge of papermaking wastewater.This study addresses the existing problems by conducting the following three studies and drawing the following conclusions:?1?Investigate different paper mills and analyze the cause of high Ca²⁺concentration in papermaking wastewater.At present,the mainstream process of wastewater treatment in paper mills is a combination of"anaerobic+aerobic+advanced treatment",and the effluent can reach the corresponding discharge standards.The main reasons for the high concentration of Ca²⁺in papermaking wastewater are:?1?Papermaking raw materials:Domestic waste paper is straw pulp,the ash content is high,and a lot of calcium-containing fillers are added during the papermaking process.?2?A large amount of domestic waste paper recycling:With the increase in the number of times of waste paper recycling,the ash content of domestic waste paper also continues to increase,causing the accumulation of calcium content.?3?Water consumption per ton of paper:With the reduction of water consumption per ton of paper,the addition of papermaking additives,high acidification of wastewater,resulting in a large number of calcium ions dissolved from ash,and the corresponding increase in calcium ions entering the wastewater treatment system.?2?Discuss the method of anaerobic granular sludge calcification control.Analyze and discuss the current anaerobic granular sludge calcification control methods for papermaking wastewater.?1?The double-alkali method is utilized to remove Ca²⁺in anaerobic influent water,which removal efficiency is high but the cost is high.?2?Adding acid to adjust the p H of the anaerobic reactor can theoretically reduce the Ca²⁺rejection rate,but the operation is complicated,and if the p H is not controlled well,it will inhibit the activity of methanogens and affect the effect of anaerobic treatment.?3?The dilution of anaerobic water in the secondary sedimentation tank can reduce the Ca²⁺retention rate,but the Ca²⁺content in the anaerobic water also increases accordingly,and the total amount of calcium absorbed by the sludge does not decrease.?4?Changing the internal structure of the reactor to remove calcium sludge promptly,the operation is simple but the sludge concentration in the reactor is difficult to control,and the anaerobic reactor runs for a long time,there will still be scaling and even clogging inside the pipeline.?3?Investigate the scale inhibition effect of"green environmental protection scale inhibitor"polyepoxysuccinic acid?PESA?on anaerobic granular sludge.After adding the scale inhibitor PESA(PESA:Ca²⁺=1:0.02?mass ratio?),the IC anaerobic reactor runs well and the treatment effect is stable.The volume load can reach 12 kg COD/?m³?d?,the average COD removal rate is 82.3%,the average value of volatile acid?VFA?in anaerobic effluent is 5.1 mmol/L,and the ratio of alkalinity to volatile acid is greater than 2?ie,ALK/VFA>2?,IC anaerobic reactor hardness rejection rate is 34.12%?The effect of magnesium ions is small,mainly based on Ca CO₃?,Ca²⁺rejection rate is 39%,total hardness?anaerobic effluent mixed solution?rejection rate is 17.21%,total calcium?anaerobic effluent mixed solution?rejection rate is 21.69%.After the scale inhibitor PESA was added,the anaerobic granular sludge V/T?VSS/TSS?showed a trend of first decrease and then increase,and the calcium content of the granular sludge showed a trend of first increase and then decrease.With the continuous addition of scale inhibitor PESA,flocculent sludge with a calcium content of 34%and a V/T value of 38.1%appeared in the anaerobic effluent.The calcium content of the granular sludge in the middle of the anaerobic reactor is10.1%,which is lower than that of the bottom granular sludge by 17.6%;the central granular sludge V/T value is 62.6%,which is higher than the bottom granular sludge V/T value by 45.7%.After the scale inhibitor PESA was added,the particle size distribution of anaerobic granular sludge did not change significantly,and the particle size of granular sludge was concentrated between 0 and 1.81 mm during the entire operation.As the particle size of granular sludge increases within a certain range,the calcium content in granular sludge increases,the V/T value of granular sludge decreases,and the insoluble matter of hydrochloric acid in granular sludge increases,which reduces the activity and treatment capacity of granular sludge.The scale inhibitor PESA is an easily degradable substance,which has better biocompatibility and lower COD contribution value.Adding scale inhibitor PESA to the IC anaerobic reactor can not only achieve good operating results and stable treatment results,but also save waste water treatment costs for enterprises.