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Study On Anaerobic Co-digestion Of Wheat Straw And Cattle Wastewater

Posted on:2013-10-03Degree:MasterType:Thesis
Country:ChinaCandidate:X F BaoFull Text:PDF
GTID:2251330398492298Subject:Environmental Engineering
Abstract/Summary:PDF Full Text Request
Using the technology of anaerobic digestion from wheat straw and cattle wastewater (WSCW) produced biogas, which could realize the win-win situation of resource utilization and pollution control. In this study the WSCW with different mass ratio, composting pretreatment and meanwhile push flow type reactor experiments were done, to achieve WSCW efficient energy conversion, increasing its biological gas production and provide a theoretical basis for straw residue reasonable applicationWith the help of laboratory,effects of cattle wastewater on anaerobic digestion process of wheat straw and characteristics of digestion with different ratios of cattle wastewater and wheat straw were studied to promote biogas production.With the raw materials of wheat straw and dairy wastewater, four treatments with the ratio of wheat straw to cattle wastewater of1:4(T1),1:3(T2),1:2(T3) and control (the ratio of wheat straw to distilled water is1:4, T4) were designed to observe the gas production, methane content and the changes of physical-chemical properties and structure before and after the fermentation in the process of fermentation. The results showed that, co-digested wheat straw with cattle wastewater was viable and gas phase was extended to two weeks, and there was no significant difference among the treatments of different proportions. The biogas yield of wheat straw was significantly influenced by the initial total solid loading (TSL) of wheat straw and decreased with the increasing initial TSL. The highest biogas yield of0.41L/g TS of wheat straw was obtained at T1, which was18.25%higher than that of T4and the average methane content is48.78%;Hemi-cellulose content of wheat straw was decreased significantly with the cellulose content of wheat straw decreased slightly,the range of the treatments is T1>T2>T3>T4. there was no significant difference between different treatments. The results of FTIR and XRD indicated that crystalline of cellulous of wheat straw was increased after anaerobic digestion and co-digestion promoted the destruction of crystalline of cellulous of wheat straw. These results suggested that co-digestion of WSCW with the ratio of1:4(based on fresh weight) was benefit for biotransformation of organic matter of wheat straw and biogas production. In order to make a quick process of composting pretreatment time on biogas production of the mixture of WSCW was studied. Four treatments with the composting time of Od (T1),3d (T2),6d (T3) and9d (T4) were designed, and then the composted mixture of WSCW were used for biogas production respectively. The results indicated that much organic matter of WSCW were decomposed during composting process and TS (Total solid) loss rate of T1, T2and T3were2.63%,11.46%and20.00%(P<0.05), respectively. The TS biogas yield of WSCW was not improved by composting pretreatment and the TS biogas yield of T2, T3and T4were103.01%,93.96%and93.68%compared to that of T1. Taking into account the impact of TS loss of WSCW during composting process, the TS biogas yield of T2, T3and T4were100.30%,83.19%and77.59%compared to that of T1. After3days composting pretreatment, the time for the rate of cumulative biogas production to total biogas production up to80%was8days shorter and the peak of daily biogas yield was2.65mL/d higher than that of control. However, when the composting pretreatment time was too long, the biogas production rate was decreased. The TS and VS (volatile solid) loss rate of WSCW were decreased with the increasing composting pretreatment time. The above results showed that, Composting pretreatment can speed up the reactor startup, the rate of gas production of wheat straw has a role in promoting to compost, the composting time of3d was the best, but improve the biogas production from wheat straw in terms of quantity, composting pretreatment can reduce raw material gas production.Based on the early stage of expriments, to the quality than the1:2WSCW mixture of raw materials, the temperature35℃, using a continuous feeding process, on a horizontal push flow type anaerobic reactor, for WSCW anaerobic fermentation mixture, to research in semi continuous feeding process feasibility and gas production effect, and provide basic data for wheat straw biogas engineering. Semi continuous feeding solid residence time (Solid Retention Time, SRT) for20d, in order to discharge biogas slurry as inoculum, the results show that:the gas production stability is in180~190mL/g, volume of gas production in0.31~0.33m3/m3·d.To sum up, WSCW withl:2~4proportion, can significantly enhanced the wheat straw raw material of wheat straw gas production, High Temperature Composting Pretreatment for3d, can improve gas production rate, the pushing flow in semi continuous fermentation process, which can realize the wheat, dairy effluent mixture of continuous methane fermentation.
Keywords/Search Tags:wheat straw, cattle wastewater, anaerobic co-digestion, biogas, composting pretreatment, push flow
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