INTEGRATING ANAEROBIC DIGESTION
AND ALGAl -BIOMASS TREATMENT PROCESSES
FOR SWINE WASTEWATER
P. Y. Yang, Professor
S. Y. Nagano, Research Associate
Department of Agricultural Engineering
University of Hawaii
Honolulu, Hawaii 96822
INTRODUCTION
Preliminary studies for integrating anaerobic digestion and algal-biomass treatment processes for
swine wastewater in Hawaii were reported previously [1,2,3,4]. These studies have indicated that integrating these two biological treatment processes is technically feasible for pollution control, bioenergy
production and utilization. However, field study in integrating these two treatment processes has not
yet been tested and evaluated. The merits attributable to this combined biological treatment process
are: (1) energy production and utilization; (2) recovery of dried anaerobically digested swine manure
acceptable as soil conditioner or fertilizer and as feed by-product for animal and aquaculture operations; (3) reuse of raceway water; (4) further removal of chemical oxygen demand (COD) and
ammonia nitrogen (NH4-N); (5) more efficient utilization of the limited land area available to producers for waste handling; and (6) power saving for mixing and aeration of algal-biomass raceway
system.
A pilot plant integrating a 20 m3 anaerobic digester and a 120 m3 algal-biomass raceway waste
management system has been completely constructed and tested at the Waialee Livestock Research
Farm, (WLRF), Hawaii Institute of Tropical Agriculture and Human Resources (HITAHR) since
1981. The purpose of this study is to develop a set of field design and operational criteria for both
anaerobic digester and algal-biomass raceway processes. After these criteria have been developed,
biogas utilization, treated effluent discharge, and by-product recovery (solid and liquid) can be properly evaluated.
MATERIALS AND METHODS
Equipment and Operational Criteria
The planning and construction of an integrated swine waste management system incorporating a
20 m3 anaerobic digester and a 120 m3 algal-biomass raceway began in March, 1981 and was completed in September, 1981. The project (0.1 ha) is located at WLRF, HITAHR, on the North Shore of
Oahu, Hawaii. The site is approximately 77 km from the University of Hawaii, Manoa Campus. The
overall research facility is shown in Figure 1.
The installation and design of the working field study at WLRF first began with a differential and
profile leveling of the entire site [5]. The slope of the land was evaluated and gradient lines were
drawn. The excavation diagrams for the digester and algal-biomass raceway were graphed on paper
and transferred to the field. Specific details for anaerobic excavation dimensions were obtained from
Hao et al, [6] in regards to digester diameter and percent of slope required for seating of the digester.
Layouts of anaerobic digester with its associated tanks and algal-biomass raceway are shown in
Figures 2 and 3, respectively.
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