SPECIAL REPORT SR-2018-01
COMPARATIVE ANALYSES OF MICROBIAL SEWAGE-BORNE CONTAMINANTS IN THE WAIKOMO WATERSHED USING A PORTABLE MULTI-USE AUTOMATED CONCENTRATION SYSTEM (PMACS)
Marek Kirs and Philip S. Moravcik
January 2018, 23 pp.
ABSTRACT
High concentrations of enterococci, exceeding the Hawaii regulatory beach-action value, have been detected throughout Waikomo Stream, Kauai by the Clean Water Branch, HDOH. A recent sanitary survey conducted by the HDOH identified ~120 wastewater injection wells and 2,200 on-site disposal systems of which about 1,600 are cesspools, in the Waikomo watershed. Environmental sources of indicator bacteria (soil, vegetation, etc.) and/or animal excreta may also be at least partially responsible for the observed exceedances. All these sources may compromise water quality in the stream and at adjacent beaches. Sewage in recreational waters poses a risk to human health, however the currently approved indicator bacteria can originate from non-sewage sources. Therefore this project focused on detection and confirmation of sewage pollution in the watershed and adjacent beaches by analyzing for microorganisms more specific to sewage, as well as by employing microbial community analysis tools. For this purpose, one liter grab samples, and 100 L samples concentrated using an ultrafiltration device were collected on 06/13/2017, 06/20/2017, 06/27/2017, and 07/05/2017 at five sites selected by the HDOH. Samples were collected from two coastal seeps, a stormwater outfall at the shoreline, and from two places in Waikomo Stream. These samples were analyzed for cultivable indicator organisms (enterococci, Clostridium perfringens, F+ and somatic coliphages) and molecular sewage markers (human-associated Bacteroides, human polyomaviruses, and pepper mild mottle viruses). Bacterial communities in the samples were compared to those typically found in sewage and human feces in Hawaii.