Optimization of Gas Transfer Coefficient (kLa) Based on Variation of Micro Bubble Technology Operation Time on Green Roof Runoff Water

Abstract

Green roof is solutions to deal with the reduction of green open areas as recharge water areas. However, green roofs still produce runoff that has low DO values that do not meet water quality standards. Micro bubbles have been proven to be effective in increasing the dissolved oxygen (DO) concentration in water. To increase the effective value and efficiency of micro bubbles, the value of the gas transfer coefficient (kLa) must be known. In this research, 4 green roof models with Chlorophytum comosum, Arachis pintoi and Portulaca grandiflora vegetation and unvegetated media will be tested to find the highest and lowest kLa values with 4 variations of treatment time (30, 45, 60 and 75 min). The highest kLa is obtained by Portulaca grandiflora runoff water with fibrous and fine root morphology in 45 min treatment with a kLa value of 0.493/min. The lowest kLa is obtained by unvegetated media runoff water with the fastest treatment (30 min) which is 0.141/min. With temperature conditions of 20°C-35°C and target DO concentration of 6 mg/L, the designed scenario of the highest kLa value of micro bubble treatment for 2.26-4.44 min, while the treatment of the lowest kLa value for 8.49-21.54 min.