Study On Biochar Activation Of Persulfate Pretreated Sludge And Its Effect On Anaerobic Digestio

Anaerobic digestion is one of the key technologies to realize sludge resource treatment.During anaerobic digestion,the composition and biodegradability of dissolved organic matter（DOM）in sludge directly affect the microbial metabolics.Improving the dissolution and release of dissolved organic matter by sludge pretreatment is the main method to enhance the efficiency of sludge anaerobic digestion.However,understanding of the composition and biodegradability of dissolved organic matter under different pretreatment methods is very limited.Therefore,the molecular transformation characteristics and biodegradability of DOM during anaerobic digestion of sludge pretreated by thermal hydrolysis were studied by using high resolution mass spectrometry(FT-ICR MS in this study.The effects of activated persulfate oxidation on sludge pretreatment,fermentation and anaerobic digestion,DOM molecular transformation characteristics and biodegradability were studied.The specific research results are as follows:（1）The DOM components in sludge after thermal hydrolysis pretreatment were mainly peptide-like,highly unsaturated and low oxygen content organic matters,while after anaerobic digestion,is the main components were lignins/CRAM-like substances.During anaerobic digestion,a small amount of aliphatic substances as CHOs compounds,peptide-like substances with high N content in CHONs compounds,such as leucine,aspartate,dipeptides,and some sulfur-containing organics in the range of O/C=0～0.3 and H/C=1～1.6 were considered as degradable organics.Whereas,most CHOs substances,such as C₁₇H₂₆O₄（Tanacetol A）and sterol lipids,peptide-like substances such as alanine,homoserine and some L-proline in CHONs,and highly unsaturated substances（lignins）,long chain fatty acids and part of cysteine in CHONSs were non-biodegradable compounds in anaerobic digestion.（2）PDS and Fe（Ⅱ）activation could increase the production of volatile fatty acids from 2391.52 mg/L to 3654.75 mg/L,and the proportion of acetic acid increased from 20%in raw sludge to 60%.To be different from thermal hydrolysis pretreatment,activated persulfate oxidatively decomposed the dissolved organic matters in sludge,especially aliphatic,unsaturated and CHOSs components containing sulfonated carboxyl functional groups,as well as fluorescent substances such as tryptophan and lysine.After oxidation pretreatment,DOM was mainly composed of CHONs compounds,and the relative abundance increased from 23.6%of raw sludge to 72.1%.Activated persulfate oxidation also affected organic matters in the process of anaerobic fermentation.The combined activation of Fe（Ⅱ）and biochar reduced the molecular numbers of DOM compounds to 85.（3）Biochar activated persulfate inhibited methane production in anaerobic digestion.Compared with thermal hydrolysis,activated persulfate oxidation effectively degraded most of the non-biodegradable CHOs substances and some substances containing carboxyl functional groups,especially the low DBE-O substances containing sulfonated carboxyl groups.Therefore,by using persulfate oxidation to reduce the refractory organic matters in sludge anaerobic digestion can alleviate the difficult of subsequent treatment of liquid from digested sludge.