County of Kaua’i Wastewater Management Division  |  Kaua'i, HI

Biosolids Management Plan

Kennedy Jenks was recently hired by the County of Kauaʻi Wastewater Management Division to prepare a comprehensive biosolids management plan for the Island of Kauaʻi. The island is currently served by four municipal and a number of small privately owned and operated wastewater treatment plants. Currently all biosolids are disposed of in the one landfill on the island, which is nearing capacity.

Previous work performed by Kennedy Jenks identified a possible market for land application of Class B biosolids at a local tree farm that grows trees to be burned as a renewable source of energy. Biosolids reuse at the local tree farm will represent a substantial savings to the County while diverting potentially 1,500 tons of waste annually from the landfill. During the course of the work it was found that the existing anaerobic digesters located in the Līhuʻe Wastewater Treatment Plant have sufficient capacity to meet the time/temperature requirements for the production of Class B biosolids with little capital expenditure. The biosolids management plan includes a phased approach for upgrading the Līhuʻe Wastewater Treatment Plant to receive additional sludge from other WWTPs on the island in addition to septage, food waste, and fats oils and grease waste for co-digestion into Class B biosolids for beneficial reuse at the local tree farm.