새로운 연구결과에 따르면 고압멸균처리기(autoclave)의 하수슬러지 전처리 방식으로 메탄의 생성을 47% 증가시킬 수 있다. 이는 염국의 혐기성 소화 관련 기업인 Aerothermal Group의 Zhengjian Wang 박사와 Nigel Baily박사의‘하수 슬러지의 혐기성 생분해의 고압 증기 멸균의 효과(Effect of Autoclaving on Anaerobic Biodegradation of Sewage Sludge)’라는 제목의 보고서의 결과에 따른 주장이다.

 

각각 다른 곳에서 탈수된 세 종류 하수슬러지를 영국 도싯(Dorset)주 풀(Poole) 지역에 위치한 회사시설에서 160℃ 환경에서 45분간  고압멸균방식으로 처리해 시험했으며, 생화학적 메탄 가능성 시험(biochemical methane potential, BMP)은 멸균 및 비멸균 방식의 하수슬러지 견본 채취 테스트를 수행했다.

 

 

 

Pre-treating sewage sludge in an autoclave can increase methane generation by 47%, according to new research.

 

The results are based on a report entitled “Effect of Autoclaving on Anaerobic Biodegradation of Sewage Sludge”, by Dr. Zhengjian Wang & Dr. Nigel Baily from British anaerobic digestion company, Aerothermal Group.

 

During the trials, three batches of dewatered sewage sludge cakes from three different sources were separately treated by autoclaving at 160℃ (5.2 bar gauge) for 45 minutes at the company’s facility in Poole, Dorset. A biochemical methane potential (BMP) test was carried out on both autoclaved and un-autoclaved sewage sludge samples.

 

A semi-continuous anaerobic digestion experiment was also conducted on both autoclaved and un-autoclaved sewage sludge samples using organic loading rates of 5 kg VS/m³/day with a hydraulic retention time of 15 days.

 

Stable conditions for digesters treating the autoclaved and the un-autoclaved sludges were achieved at this loading rate with bio-methane production from digesting the autoclaved sludge up to 47% more than that from treating the un-autoclaved sludge, according to the company.

 

The experiments were carried out in duplication for each tested sample. Two inoculum control digesters were also run alongside, fed with seed sludge and tap water only. The inoculums were prepared by screening (1mm mesh) out large inert and undigested substrates.

 

Three batches of sewage sludge cakes were collected and separately autoclaved at a temperature of 160C (5.2 bar gauge) for 45 minutes. After autoclaving, the sludge masses were increased 1.3~1.5 times due to the addition of water (from steam condensing). Also after autoclaving, the sludge was said to have a more homogenous slurry-like appearance (brown in colour) and was less odorous, said Aerothermal Group.

 

It was concluded that stable digester operation is possible at a loading rate of 5 kg VS/m³/day, and under these conditions, an autoclaving pre-treatment for anaerobic digestion of sewage sludge cake could increase bio-energy production by over 45% and facilitate the easy co-processing of multiple ‘problematic’ streams, such as screenings and scum.

 

Christian Toll, CEO of AeroThermal, said: “We are very excited that we have proven that the British designed and built, AeroThermal hydrolysis system, is an efficient way to produce a higher yield of methane gas, through autoclaving of sewage sludge cakes, to potentially be used as a source of green energy and at the same time go some way to solving the waste problem which is so damaging to our environment.”

 

 

[출처 = Water World / 2015년 7월 13일]