| China is a big country in the production and processing of rosin,with an annual production of more than 1.4 million tons of rosin products.The waste water produced during the processing of rosin contains a large amount of emulsified rosin,resin acid,turpentine,phenols and tannins,etc.,resulting in poor biodegradability of the waste water,difficulty in direct biodegradation,and difficult treatment.In this project,a small-scale test is carried out for the characteristics of high COD,high SS and high chroma of wastewater.The water quality and quantity of wastewater,small-scale test results and discharge requirements are integrated,and the pre-treatment of "oil separation + coagulation air flotation + Fenton oxidation" is adopted.The treatment process removes a large amount of SS and COD in the wastewater,and reduces the chromaticity and decomposes large molecules that are difficult to decompose to improve the biodegradability of the wastewater.Then,the organic pollutants in the wastewater are deeply treated through "UASB + Biological Contact Oxidation",so that the wastewater is discharged stably to meet the standard.(1)Through the screening test of aluminum sulfate,ferric chloride,PFS and PAC,it is found that the coagulant PAC is the best coagulant,and the treatment effect of the combined coagulant aid PAM is better.Comprehensive experimental results determined that the optimal conditions for the coagulation test were pH=8,PAC dosage of 200 mg/L,PAM dosage of 4 mg/L,and stirring time of 15 min.The removal efficiency of COD and SS in wastewater were 35.8% and 80.9%,respectively.(2)Perform Fenton oxidation test on the effluent of the coagulation test.According to the results of the test,it is determined that the optimal conditions for the Fenton oxidation test are pH=4,hydrogen peroxide dosage 4 m L/L,and ferrous sulfate dosage 1.5 g/L,reaction time is 2 h,the removal of COD in wastewater is36.9%.(3)Perform an enhanced coagulation precipitation test on the effluent of Fenton oxidation,adjust the pH value of the wastewater to weak alkaline,and add coagulant PAC and coagulant aid PAM to the wastewater to further improve the removal rate of COD.According to the experimental results,the optimal conditions for the coagulation test are as follows: pH=8,PAC dosage of 100 mg/L,PAM dosage of 2mg/L,stirring time of 15 min,the removal rate of COD in wastewater 12.4%.(4)The pretreated wastewater enters the UASB,and the pH of the influent is controlled to be 6.8～7.2,the temperature of the influent is about 25 ℃,and the low concentration is used to start,and the COD concentration of the influent is gradually based on the COD removal efficiency.The commissioning process needs to strictly monitor the concentration of VFA in wastewater,and maintain the concentration of VFA below 200 mg/L to avoid acidification of UASB.After commissioning,the COD concentration of UASB’s effluent is between 500 mg/L and 700 mg/L.The removal rate of wastewater COD is stable between 75% and 80%.(5)The effluent of UASB enters the biological contact oxidation tank to control the dissolved oxygen at 2～4 mg/L.The COD concentration of the anaerobic tank effluent is less than 100 mg/L,and the removal rate of wastewater COD is stable at more than 80%.(6)This project adopts the combination method of "oil separation + coagulation air flotation + Fenton oxidation + UASB + contact oxidation" to treat rosin processing wastewater.After 90 days of commissioning and operation,the system is running well and has stable water output.The average treatment efficiency of the entire system for COD,SS,and chroma is 98.8%,97.1%,and 99.3%.The effluent COD concentration is less than 100 mg/L,SS concentration is less than 70 mg/L,and chroma is less than 50 times,all reaching "Comprehensive Wastewater Discharge Standard" GB8978-1996 middle-level standard.(7)After the normal operation of the wastewater treatment station,the cost per ton of wastewater is 14.29 yuan based on the actual dosage of the commissioning and operation,electricity costs,and labor costs.It has high engineering reference value for similar rosin processing wastewater. |
