| With the growth of wastewater treatment rate,the excess sludge production rapidly increased.which contain a large amount of organic carbon,pathogens,heavy metals and other substances for human survival ecological environment had a huge impact.Therefore,it needs to stabilize before the ultimate disposal.Currently,anaerobic digestion is the most common sludge stabilization treatment methods.However,in order to maintain required temperature of anaerobic sludge digestion will need a large of extra energy.Because of fossil fuel tensions and brought serious environmental pollution,an urgent need for low-power input anaerobic digestion.in addiation,there are rich in salt lake and solar energy in china.Thus,the present study was conducted a system(salt-gradient solar pond coupled sludge anaerobic digestion)for sludge treatment.The main conclusions as follows:The results showed that:the solar ponds contained 1-3 layers NCZ are ideal solar ponds.The LCZ temperature of solar pond containing one-NCZ-layer could rise to 45℃,eventually stabilized at 49.6±3.1℃.the gradient layer gradually spread from the obvious salt gradient layers to stable salt gradient layers.Based on the need of actual project,the solar pond contained one NCZ layer can obtain both of high performance of collector and thermal storage,and reduces the cost of building.In the study of coupled single-phase anaerobic digestion with solar pond,the temperature in R1 reached 50℃after 68 h.Compared the results of effluent in R1 and R2,showed that after 30 days’ treatment,the R1 removed 65.01±4.15%of total chemical oxygen demands(TCOD),while the R2 removed 39.76±4.42%of TCOD;and produced 18505mL biogas which was about 4.5 fold of R2 producing;The concentrations of soluble chemical oxygen demand(SCOD),protein,saccharides,and ammonia in reactor R1 were always higher than those in R2.The average concentration of SCOD were 1683.27mgL-1 and 664.01mgL-1,and soluble protein,carbohydrate peak concentrations were 297.6±15.4 mg L-1 and 332.4±14.7 mg L-1,which improved 150 mg L-1 and 167 mg L-1,respectively,than R2,suggesting thermophilic condition of R1 enhanced the hydrolysis process of sludge organic matter.In the study of coupled two-phase anaerobic digestion with solar pond,the temperatures of two-phase reactor and single-phase reactor were 52.53±1.52℃and 51.58±1.46℃,respectively.It showed the two system both operated at thermophilic digestion conditions.Compared the treatment efficiencies of two-phase anaerobic reactor and single-phase anaerobic reactor,the removal rates of TCOD were 79.76±4.4%and 65.01±4.15%,respectively.In the acidogenic phase,accumulation of organic acids in the acidogenic bacteria made a suitable acidic environment,and in methanogenic phase that pH value increased from 6.5 to 7.2,which was suitable for methanogens bacteria,so that the process of anaerobic digestion two-phase hydrolysis reaction inside a more thorough,higher methane conversion rate.The concentration of acid production phase SCOD,proteins,carbohydrates and soluble ammonia and other substances were significantly higher than single-phase reactor.The total accumulative biogas yield reached 22455mL in two-phase system,while the 16215mL biogas in single-phase system.The results showed that the system of thermophilic digestion coupled with solar pond had significant advantages for domestic wastewater treatment plant sludge resource reduction processing in future. |
