| dc.description.abstract | Many researchers consider efficient harvesting is the major bottleneck in cost efficient production of microalgae, contributing 20 – 30 % to total production cost.
This thesis is the conclusion of a two years research project to develop Salsnes Water to Algae Treatment (SWAT) harvesting technology. SWAT uses two main processes: flocculation and filtration. The SWAT objectives were achieved, 95 % algae removal and power consumption lower than 0,08 kWh/m3.
To gain knowledge about harvesting algae, an overview of coagulation and flocculation principles, coagulation using metal ions, mixing procedures, microalgae species, microalgae flocculation and finally a general view of different harvesting technologies focusing on filtration was carried out.
PAX-18 and Chemifloc CM25 were selected for coagulation and flocculation respectively. Four different flocculator configurations were designed and tested, the best configuration (20 liters rapid mixing tank and 100 liters slow mixing tank) was chosen for further experimentations.
The PAX-18 concentration used was 114 mg/L as average and the Chemifloc CM25 concentration used was 4 mg/L.
Growth microalgae conditions (pH, temperature and dissolved oxygen concentration) were measured continuously during tests. Also key parameters for SWAT technology development were measured: power consumption kW/h, water level set point (mm), algae flow rate (m3/h) and cleaning procedure.
Different mesh pore sizes for filtration were investigated, resulting in an optimal mesh pore size for 210 and 250 μm.
Filter efficiency was determined using total suspended solids (TSS) and turbidity removal.
Finally, there is a need of lowering coagulant dosage, so several recommendations are given to improve SWAT performance and make it a marketable technology. | nb_NO |
