20    CASE STUDY FOR FRUIT FLY FACILITY
WASTEWATER MANAGEMENT: AGRICULTURAL
PROCESSING FOR LAND LIMITED CONDITIONS
J. Tao, Graduate Research Assistant
P. Y. Yang, Professor
Dept. of Biosystems Engineering
University of Hawaii
Honolulu, Hawaii 96822
ABSTRACT
A fruit fly facility on the island of Oahu, Hawaii was investigated for its wastewater characteristics and treatment/disposal alternatives. Based on wastewater characteristics and bench-scale
study, an on-site intermittently-aerated batch operated treatment was installed to treat the fruit fly
wastewater. With F/M ratios maintained at the level of 0.2 g COD/g MLSS/day or below, a more
than 90% removal of influent COD can be achieved. The system also achieved average total nitrogen, total phosphorus, BOD5, TSS removal efficiencies of 86%, 60%, 98%, and 92%, respectively. The overall system performance and cost analysis showed that this treatment system had
very stable and excellent operational performance while physically it was very simple, economical, and land saving for an on-site small wastewater treatment system. This treatment system integrated with the existing irrigation system successfully provides the most effective wastewater
treatment/reuse management solution among all alternatives currently available to the fruit fly
facility.
INTRODUCTION
Agricultural processing wastewater can be high or low volume of wastewater flow with high
organic content compared to domestic sewage. Management of the agricultural processing wastewater with land-limited conditions is rather difficult, especially when it cannot be discharged
into the existing domestic sewer system and only limited land is available for final disposal. The
Fruit Fly Rearing Facility, owned by the California Department of Food and Agriculture
(CDFA), located on a limited farm land on the island of Oahu, Hawaii, produces sterilized fruit
flies for biological control of fruit fly infestation. It also creates high organic content of wastes
and wastewater.
The facility experienced great difficulties in managing the wastewater disposal ever since the
wastewater was no longer allowed to be discharged into the sewer system. Drip irrigation of the
untreated wastewater for a 7-acre farm area was initially approved by Hawaii State Department
of Health. After the operation period of over a year, a final approval of this practice was still unattainable because the performance of the installed irrigation systems could not meet the state
regulatory requirements. The high concentrated wastewater caused the development of anaerobic
conditions in the soil, rock, and pipelines as well as the storage tanks. This generated tremendous
obnoxious odor and attracted flies in the field and around the irrigation system, not to mention
other adverse environmental impacts and maintenance problems. It is required that an appropriate management of the wastewater generated from the fruit fly facility needs to be developed for
the protection of the environmental quality.
This paper explains how a biological wastewater treatment system was integrated into the existing irrigation system for an effective fruit fly wastewater management over the period of September, 1995-August, 1996.
52nd Purdue Industrial Waste Conference Proceedings, 1997. Ann Arbor Press, Chelsea, Michigan 48118. Printed in
U.S.A.
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