Anaerobic digestion of wastewater from the production of bleached chemical thermo-mechanical pulp : higher methane production for hardwood than softwood

• BACKGROUND: Chemical thermo-mechanical pulp (CTMP) mills holds a large biomethane potential in their wastewater. Their broadened market has involved increased bleaching and utilisation of different raw materials. Therefore, the main aim of this study was to obtain and maintain a stable anaerobic digestion (AD) process, with a high methane yield and total organic carbon (TOC) reduction, when digesting CTMP wastewater, from different production protocols including shifts in raw material and bleaching. A lab-scale upflow anaerobic sludge bed (UASB) reactor was used for the tests.RESULTS: The variations in raw material (aspen, birch and spruce) and consequently in TOC-loading (3.6-6.6 kg TOC m-3 and day-1) did not affect the UASB process negatively. Methane production values from 360 to 500 NmL g TOC-1 were obtained, with the highest yield for wastewater from the production of birch- followed by aspenand spruce pulp. The acetic acid and fTOC reduction ranged 90 to 95% and 61 to 73%, respectively.CONCLUSIONS: The stable process performance maintained during shifts in raw material for pulp production show that AD is feasible for CTMP mills with a diversified product portfolio. Furthermore, the increased use of hardwood and bleaching will most likely increase their potential as a biomethane producer.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Vattenteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Water Engineering (hsv//eng)

Nyckelord

biogas

wastewater treatment

UASB

CTMP

softwood

hardwood

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)