Biochar enhanced nitrite accumulation during sulfur autotrophic denitrification
Sulfur autotrophic denitrification(SADN)can provide NO2--N for anaerobic ammonia oxidation(Anammox).In order to promote the accumulation of NO2--N in SADN process,this study used S0 as the electron donor and investigated the effects of sludge/coal gangue-derived biochar(SCBC)on the NO2--N accumulation rate and shock resistance in SADN system.The results illustrated that the addition of SCBC increased the NO3--N reduction rate in SADN from 70.6 mg·L-1·h-1 to 107.7 mg·L-1·h-1,and the NO2--N reduction rate increased from 30.5 mg·L-1·h-1 to 35.1 mg·L-1·h-1,resulting in an increase in the NO2--N accumulation rate from 48.2%to 63.0%.When subjected to a shock load of 300 mg·L-1 NO3--N,the reduction performance of SADN initially decreased,but recovered gradually after 6 days,and continued to increase,compared to12 days without the addition of SCBC.After 60 days,the PN/PS and PN values were 3.51 and 5.27 mg·g-1,respectively,higher than those without SCBC addition,which were 2.36 and 3.44 mg·g-1,respectively.The denitrifying bacteria Thiobacillus,Sulfurimonas,and Thermomonas were detected by high-throughput sequencing analysis.SCBC supplementation enhanced these bacteria,increasing their proportions from 40.0%,0.61%,and 0.03%to 51.8%,2.71%,and 3.47%,respectively.In conclusion,SCBC addition presents a new avenue for NO2--N accumulation in SADN treatment,while also offering a novel strategy for sludge and coal gangue utilization.
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