Reclamation – A Great Idea, Little Used

posted in: October 1992 | 0

In the 1970s, Maui County made a sound decision: to avoid using outfalls for disposal of effluent from its sewage treatment plants. The effluent was to be used instead for irrigation – it would be “reclaimed.”

Thus, each of Maui’s three sewage treatment plants is officially called a reclamation facility. Its wastewater division calls itself a Wastewater Reclamation Division. On every piece of stationery; on every plant sign, tribute is paid to the notion of reclaiming a resource as opposed to wasting it.

Unfortunately, those are about the only places “reclamation’ is to be found.

Everyday Emergencies

When the county built its sewage treatment plants, the injection wells in every case were to be used for emergencies only. In the case of the Lahaina plant, for example, it was anticipated by the county that the wells would be used no more than approximately two weeks a year – when demand for irrigation water was low for instance, or when other problems arose that precluded the effluent’s use for irrigation.

But the market for effluent was not there. As a result, the reservoir built to hold effluent at the Lahaina plant – paid for largely by federal funds – fell into disuse and all of the 4 to 5 million gallons of effluent handled on an average day are pumped to the wells. (Whether Maui County will have to reimburse the Environmental Protection Agency for its portion of the costs of reservoir construction is a matter of ongoing talks. Evidently the county now wants to refurbish the reservoir, anticipating once more that it will have a market for the effluent.)

No takers were found for the effluent from the Kahului plant, which handles about 6 million gallons a day, on average.

Only the Kihei plant has a steady market for effluent in any meaningful quantity Between 600,000 and 800,000 gallons a day (of an average daily flow of roughly 3 million gallons) are used for golf course irrigation. Some effluent also is piped to Kalama Park.

Diminishing Returns

Whatever the links may be between injection wells and algae blooms, there is no denying the fact that the daily use of injection wells has diminished their capacity to handle effluent flows. Most wells are cased for the first 100 or 50 feet below the surface; after that, the effluent is free to flow into such fissures, cracks, or pores in the underlying rock as may exist.

On the whole, the effluent is treated to standards well beyond those required by the state. Still, there is enough “stuff” in the effluent to clog up the wells over time and thus reduce their capacity. Frequently, the county will blow air through them or pour caustic soda down the holes. This is not sufficient to restore the wells to their original capacity, however.

The loss of capacity has been dramatic. In Lahaina, the existing four wells were originally estimated to have a total capacity to handle 24.4 million gallons of effluent a day (Wells 1 and 2, drilled in 1975, had a total capacity of 9.2 million gallons; wells 3 and 4, drilled in 1985, each had a capacity of 7.6 million gallons, or a total of 15.2 million gallons.) The present total capacity of the wells ranges from 4.5 million to 9 million gallons. In other words, the volume of effluent that the plant can handle has been cut more than 60 percent.

In Kahului, well capacity has been similarly reduced. However, because the county failed to place flow meters on the wells (in violation of state regulations), the capacity of each well cannot be known. (The county claims it has since installed the flow meters.) Last year, the county received permission to drill four new wells, although the tests to determine their capacity are only now being done.

Getting Religion

Recognizing the need to wean itself off injection wells, the county retained a consultant – Brown and Caldwell – to study markets for effluent in the Lahaina area. The study, completed in May 1992, found that it cost more to reuse effluent than it did to get water from brackish wells ($470 to $640 per acre foot, as opposed to $150 to $250 per acre foot for well water). If, however, costs of reclamation were compared to potable water costs ($900 per acre foot), the advantage was clear.

Three alternatives for reclamation were described, but all fell short of consuming 100 percent of the daily effluent flow. Moreover, before the effluent can be reused, high salinity levels that characterize present flows have to be brought down. (This might be achieved if the county were to get a handle on the problem of infiltration and inflow, whereby brackish water enters the sewer collection system through breaks in sewer mains.)

Brown and Caldwell assessed the market by surveying the following water users in the Lahaina area: Amfac, the county Department of Parks and Recreation, Kapalua Resort, the state Housing Finance and Development Corporation, and the state Department of Transportation. Of those, “only the Department of Transportation reported no potential for reclaimed water use in the study area.”

Volume 3, Number 4 October 1992