Many people do not realize that there is an oasis of tranquility in the middle of the bustle of Honolulu airport. These Cultural Gardens have been a landmark feature at the Honolulu International Airport since 1969. The gardens feature three fishponds containing koi (decorative carp to non-Hawaii readers) and other fish. These include the so-called Chinese and Japanese ponds, and the larger Hawaiian pond. The gardens with their ponds provide a beautiful and restive environment for travelers to enjoy while transiting through the airport. The gardens and ponds were upgraded to their present form around 1981.

Unfortunately the ponds have on-going water quality issues. With abundant inputs of nutrients from the fish waste and food, and sunshine, there is a constant battle with algae and ammonia buildup. There are three independent filtration systems servicing the ponds. Despite this and a costly maintenance program the quality of the water in the ponds is sometimes poor. In addition, fresh water use is apparently high.

In 1983, an attempt was made to improve the water quality by installing sand filters and extending the waterfall features to promote attached growth filtration. Later, ozone units were installed to inject ozone gas into the ponds in order to control algae and other deleterious growth. The sand filter was marginally effective and the ozone treatment was not effective. Today, the sand filters remain in operation but the ozone units are no longer operational.

A service contract to clean the ponds is currently in place. The primary function of the contract is to remove debris and deleterious growth from the ponds on a semi-monthly basis. Algae growth has been the primary problem. If left unchecked, the algae will take over the pond within days. This turns the ponds into a stringy green soup with a foul odor. Chemical control is not a feasible option as it would be toxic to fish and beneficial micro flora. Additionally, the overflow from the ponds discharges into drains which lead to State waters. Most chemicals, such as peroxides and chlorine are marine toxins, and are prohibited from direct discharge unless associated with a dechlorination process to reduce concentrations to acceptable levels.

The overall objective of this study is to determine a cost-effective, innovative and sustainable treatment system which improves water quality and reduces maintenance, water wastage, and energy use through the use of photovoltaic panels to supply power to the system. In order to optimize operation and maintenance of the ponds, it is necessary to determine existing inadequacies and develop innovative solutions. Pond maintenance involves removal of ammonia to maintain concentrations below those toxic to fish, control of algae for water clarity, and reduction/removal of sediment. In the area of biological treatment in particular, there are several potential alternatives which may be more robust and effective than the existing system. Regarding the maintenance of water clarity, the use of ultraviolet (UV) sterilizers is currently being effectively used at other locations to control algae and enhance water clarity. However, appropriate dosage and affects on nitrification (ammonia control) must be determined.

Treatment Evaluation:

Ultraviolet Light is a cellular treatment process which inhibits further growth by altering the genetic code of algal cells through exposure at specific dosages. Once altered, the algae cannot reproduce and thus their population is controlled. Similar to ozone, UV is non-discriminatory and may be detrimental to beneficial bacteria. Specifically, nitrosomas and nitrobacter bacteria are of particular importance because they convert ammonia to nitrites and nitrates. Without such bacteria, the ammonia, a byproduct of the fish, may eventually kill them unless they are fixed and rendered harmless. Unlike the ozone unit which simply injected ozone into the ponds, we propose to evaluate a sidestream UV system to determine the return rate which would be sufficient to control algae growth without severely impacting ammonia removal.

Energy Considerations:

Because UV generation requires an electrical power source, electrical consumption may be an important factor when considering the economic feasibility of a full scale operation. Consistent with current efforts by the State to move toward green technology, research into the feasibility and reliability of utilizing solar panels to supplement electrical demand will be evaluated.