Integrating an anaerobic Bio-nest and an aerobic EMMC process as pretreatment of dairy wastewater for reuse: a pilot plant study |
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Authors: | Piyalerg Kongsil Joshua Lelemia Irvine P Y Yang |
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Affiliation: | (1) Graduate Program in Bioengineering, Department of Molecular Bioscience and Bioengineering, University of Hawai’i at Mānoa, Honolulu, HI 96822, USA;; |
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Abstract: | A large dairy farm located on the island of Oahu, Hawaii was the site for an investigation for the potential integration of
the existing facultative lagoon system with a cost effective pretreatment unit process. Based on the results from a laboratory
study, a pilot plant was installed with two anaerobic bioreactors (10 m3 each) and one aerobic reactor (3.8 m3). Two layers
of media “Bio-nest,” providing a void volume of 98%, were placed into each anaerobic bioreactor with 19% space-based on the
bioreactor water volume. For better performance and reduction of shock-load, the equalization/settling tank was employed prior
to the first anaerobic Bio-nest reactor. The intermediate holding tank settled effluent suspended solids from the Bio-nest
reactor and adjusted the loading rate in order to improve the performance of the aerobic EMMC (entrapped mixed microbial cell)
bioreactors. Based on the start-up operation of the Bio-nest system at an organic loading rate of about 1.5 g TCOD/l/day,
the production rate of biogas from the first and second Bio-nest reactors was 0.64 and 0.15 l/l/day, respectively. This indicates
that the anaerobic degradation of organics occurs mainly in the first Bio-nest reactor due to the low loading rate. The removal
efficiency from the Bio-nest system shows TCOD removal of about 70%. The EMMC process provided further treatment to achieve
a removal efficiency of TCOD at about 50% and a TN of about 35%. The cost for these pretreatments in order to be integrated
with the existing lagoon system is US $1.1 per 1,000 gallons (3.8 m3) for dairy wastewater and $1.1 per 1,000 gallons (3.8 m3) for dairy wastewater and 91 for each ton of TCOD removal.
This integration system provides a sustainable improvement of environment and agricultural production. |
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