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Performance Evaluation of a Wetland-Type On-Site Wastewater System

Roger W. Babcock, Jr., Danielle Restelli, Trevor Yatomi, Cody Tallman, and Kanoelani Yadao

December 2021, iv + 46 pp.


The Ridge to Reefs (R2R) Bioreactor Garden (BG) is a constructed wetland (CW) type wastewater system that was evaluated at the East Honolulu Wastewater Treatment Plant (EHWWTP). A pump, plumbing, electronic valves, dosing tank with float switch, and a programmable logic controller (the “system”) were fitted to the R2R-BG. The system withdrew screened raw wastewater from the EHWWTP influent channel as influent and treated effluent was discharged into the EHWWTP sewer. The system was designed to provide a total flow of 600 gal/day to the Bioreactor Garden in a manner prescribed by the National Sanitation Foundation Standard 40 (NSF40) and 245 (NSF245) test protocols. The NSF40/245 protocols call for 35% of the daily flow to enter between 6 am and 9 am, 25% to enter between 11 am and 2 pm, and 40% to enter between 5 pm and 8 pm. The protocol calls for a sixteen-week continuous design loading period followed by a series of four stress loading tests over 7.5 weeks and a final 2.5 weeks of design loading.


Performance Evaluation of a Cyclic Biological Wastewater Treatment System

Roger W. Babcock, Jr., Danielle Restelli, Trevor Yatomi, Cody Tallman, and Kanoelani Yadao

November 2021, iv + 45 pp.


The International Wastewater Technologies, Inc. Cyclic Biological Treatment (CBT) System wastewater treatment unit was evaluated at the East Honolulu Wastewater Treatment Plant (EHWWTP). A pump, plumbing, electronic valves, dosing tank with float switch, and a programmable logic controller (the “system”) were fitted to the CBT. The system withdrew raw wastewater from the EHWWTP influent channel as influent and treated effluent was discharged into the EHWWTP headworks. The system was designed to provide a total flow of 800 gal/day to the CBT in a manner prescribed by the National Sanitation Foundation Standard 40 (NSF40) and 245 (NSF245) test protocols. The NSF40/245 protocols call for 35% of the daily flow to enter between 6 am and 9 am, 25% to enter between 11 am and 2 pm, and 40% to enter between 5 pm and 8 pm. The protocol calls for a sixteen-week continuous design loading period followed by a series of four stress loading tests over 7.5 weeks and a final 2.5 weeks of design loading.


2021 Hawai‘i Cesspool Hazard Assessment & Prioritization Tool

Michael Mezzacapo

August 2021, 97 pp.


Cesspools are a substandard sewage disposal method and widely recognized to harm human health and the environment. The state of Hawai‘i has an estimated 82,000 cesspools. To address pollution concerns, the Hawai‘i State Legislature mandated replacement of all cesspools by 2050. A major step in achieving this goal is to categorize cesspools based on potential or realized harm to humans and the environment. This report details a comprehensive tool designed for this purpose. After researching similar efforts, methods and datasets were chosen that met the needs of state government, cultural values, and environmental sensitivities. The Hawai‘i Cesspool Prioritization Tool (HCPT) was developed by integrating fifteen risk-factors that either control or relate to how cesspool impacts are distributed across communities and the environment. These factors were processed with a geospatial model to calculate a single prioritization score for every cesspool in Hawai‘i. Because sewage pollution impacts are cumulative, individual scores were consolidated by census boundary areas. Results from the HCPT prioritization were validated through comparison with a statewide assessment of nearshore wastewater impacts funded by Hawai‘i Act 132. Future data, organized within census area frameworks, can be layered onto the results to address equity and outreach challenges.

The HCPT was designed to be as objective as possible with prioritization based solely on the relationships between datasets, thereby reducing human bias as much as possible. All data used in the HCPT is at the statewide scale, normalized, and based on regulatory rules or modeling outputs. The total number of cesspools in the state categorized as Priority Level 1 was 13,885, with 13,482 and 54,058 as Priority Level 2 and Priority Level 3, respectively. Approximately 35%, 7%, 21%, and 37% of cesspools in the Priority Level 1 group are located on O‘ahu, Maui, Kaua‘i, and Hawai‘i Island respectively.


Microbial Indicators, Sewage Markers, and Human Pathogens in Hawaii Streams

Marek Kirs
September 2021, vi + 71 pp.


The overarching goal of this study was to support and improve application of protective and meaningful microbiological recreational water quality standards in Hawaii. Eighty samples were collected from a total of nineteen watersheds on Hawaii Island, Kauai, Maui, and Oahu. The samples were analyzed for concentrations of indicator bacteria (total coliforms, Escherichia coli, enterococci, Clostridium perfringens, F+ and somatic coliphages) and pathogens (Salmonella and Campylobacter) by cultivation-based methods, and for concentrations of sewage markers (crAssphage, HF183, HPyV, PMMV) and human enteric viruses (adenoviruses, enteroviruses, noroviruses GI and GII, rotaviruses) by molecular methods (qPCR and RT-qPCR). High concentrations of enterococci (78.8% samples exceeding the 130 MPN/100 ml Beach Action Value, averaging from 47 to 6,801 MPN/100 ml) were observed in the watersheds. Ten out of nineteen (53%) watersheds were positive for at least one human marker. In the samples positive for sewage markers (32.5%), sewage input appears to be relatively low as no enteric viruses (adenoviruses, enteroviruses, noroviruses GI and GII, rotaviruses) were detected. This prevented application of risk analyses models. Clostridium perfringens and somatic coliphage concentrations appear to discriminate between the samples impacted or not impacted by sewage as well as between the samples positive or not positive for Salmonella and Campylobacter, supporting its value as a sewage tracer. Although limited rainfall was observed, concentrations of sewage markers and bacterial pathogens were not influenced by rainfall, while concentrations of indicator bacteria were. From all the microbial parameters studied, F+ coliphage concentrations correlated positively with the onsite sewage disposal systems (OSDS) density. Novel qPCR assays for F+ RNA coliphage subgroups were developed and used to analyze the samples. Improving the recovery of enteric RNA viruses would strengthen further studies.


Denitrifying Leachfields:  Enhanced Nitrogen Removal from Domestic Wastewater in Hawai‘i

Roger Babcock Jr., Michah Tang, Tracey Panlasigui, and Julien Sassi
January 2021, vii + 21 pp.


Act 125 bans all cesspools in Hawaii by 2050, which means that at least 88,000 known cesspools on individual homesites must be upgraded. More than half of these cesspools are located in areas where there is the potential impact of nitrogen on drinking water and/or nearshore marine reef environments. These cesspools will need to be replaced by individual systems (< 1,000 gpd) that are capable of at least 50% nitrogen removal (as required by NSF254 and DOH rules). Denitrifying leachfields, also called denitrifying absorption beds or nitrogen reducing biofilters (NRBs), are a conventional absorption bed disposal system that is upgraded to achieve significant nitrogen removal in a passive, non-mechanical, no-energy manner. The NRB can allow a simple septic tank + absorption system to passively achieve nitrogen removal performance that would normally require a much more expensive advanced nitrifying/denitrifying aerobic treatment unit (ATU-N/DN). NRBs have been studied and developed in the eastern US, including Florida and New York, and one state already has a design criteria in their wastewater design rules. No testing/validation of NRBs has been conducted in Hawaii and thus their use is not yet possible for nitrogen removal. The soil conditions, available media, and temperature conditions (no cold winters) in Hawaii require that local design criteria needs to be developed via testing. As a first step, prior to full-scale field testing that must be conducted, a series of 14 laboratory-scale NRBs were constructed with different types of absorption bed media, with different depths, and continuously operated for 14months. The NRBs remained in operation, except for 7 columns that were disassembled for inspection after 14 months of operation. A series of 18 new columns with additional types of locally available media recently began operation (25 columns in total). The bench-scale testing is very important to frame the scope of the future full-scale field tests.


Microbiological Water Quality of Ko Olina Lagoons

Marek Kirs and Jaline Sergue
May 2020, viii +1 8 pp.


The Ko Olina Resort lagoons are extremely popular for recreational activities, however, they have not been extensively monitored for water quality. The objective of this study is to address this lack of water quality information by examining and evaluating the lagoons’ microbiological water quality over a one-year period. In 2019 (January 14 to December 11), 128 water samples were collected from the four lagoons (Kohola, Honu, Nai‘a, and Ulua). The results indicated generally good water quality as (1) enterococci were not detected in a large proportion of the samples (88%), and (2) only one sample exceeded the Hawai‘i Beach Action Value for enterococcus concentrations (130 MPN per 100 ml). In addition, no human-associated Bacteroides marker was detected in this sample, nor were Clostridium perfringens concentrations elevated, which suggested the source was not human fecal matter. The areas of brown water found in late August 2019 in the Kohola and Nai‘a lagoons were due to the extensive growth of a dinoflagellate, tentatively identified as Gymnodinium. Fecal indicator bacteria (enterococci and C. perfringens) were not associated with the blooms. The saxitoxin levels were low (0.039 µg per L) in all four lagoons and were not associated with the observed blooms, nor did it present any plausible direct risk to human health. The localized blooms were probably linked to the elevated nitrogen levels associated with the two lagoons. The blooms may possibly have resulted from the extensive use of irrigation and fertilizers during the dry summer months, and local hydrology and water exchanges may have also contributed to the observed differences. The linkage between irrigation sources, fertilizer use, and local hydrology should be further studied to more definitively determine the cause of the dinoflagellate blooms if mitigating periodic nuisance blooms in the Ko Olina lagoons is of interest.

Identifying Potential Knowledge Gaps for Hawai‘i’s Cesspool Conversion Plan

Michael A. Mezzacapo
March 2020, 85 pp.


Cesspools are widely used as a sewage disposal method across the Hawaiian Islands. However, cesspools lack adequate treatment of waste to protect the surrounding environment from dangerous pathogens and nutrients. Each day, approximately 88,000 cesspools across Hawai‘i release nearly 55 million gallons of sewage into the ground, much of it reaching groundwater. This report assembled a comprehensive list and analysis of research studies pertaining to the status of wastewater pollution —with an emphasis on cesspools— and associated impacts on water resources, nearshore ecosystems, and human health. Many of the studies discussed within this white paper provided valid scientific evidence to support the creation of a long-range statewide cesspool conversion plan. Knowledge gaps in areas such as hydraulic/hydrologic modeling and technological methods were identified, with additional limitations in identifying and tracking specific wastewater sources. Many of these limitations, however, can be overcome. For example, limitations in identifying particular sources of wastewater pollution using %N and δ15N can be supplemented with available land-use information and source tracking information to clarify concentration and isotopic data of nitrogen. Resource management presents many challenges, including the recognition of diverse societal views and values. To overcome discrepancies in available data and varying societal values, the use of transparent, adaptable framework methods such as “structured decision making” offers approaches for problem-solving. Such frameworks are consistent with a holistic management approach to onsite wastewater management that incorporates the natural and social sciences to identify and address barriers as a method to reduce negative impacts.

A copy of the report may be viewed at the Hawai’i Department of Health Cesspool Conversion Working Group Website. Click here to view the report.

Multi-State Regulation and Policy Survey of Onsite Wastewater Treatment System Upgrade Programs

Michael A. Mezzacapo
September 2019, xi + 84 pp.


This report was commissioned by the Cesspool Conversion Working Group (CCWG) to evaluate and analyze cesspool and conventional on-site wastewater treatment system (OWTS) conversion methods in other states. States were chosen based upon proximity to a coastal environment, the number of cesspools, and recent legislation. Six states were evaluated based upon criteria approved by the Data and Prioritization Subgroup of the CCWG. This document briefly summarizes other state efforts, policies, and procedures regarding OWTS upgrades and not meant to be an exhaustive report on state OWTS regulations. The document is organized by state and subdivided into eight categories: (1) regulation overview, (2) regulation enforcement and requirements, (3) methods to determine priority conversion areas, (4) methods to identify impaired waters, (5) nutrient reduction science, (6) conversion technologies/future approval, (7) conversion method and timelines, and (8) funding mechanisms.

A copy of the report may be viewed at the Hawai’i Department of Health Cesspool Conversion Working Group Website. Click here to view the report.

Microbial Indicator Bacteria in the Kahaluʻu Watershed

Marek Kirs, Roberto A. Caffaro-Filho, and Philip Moravcik
July 2019, vi + 32 pp.


In Hawaiʻi, enterococci grow in extra-enteric environments (such as moist soils, vegetation, etc.) therefore our streams contain naturally high levels of enterococci and the water quality standards (geometric mean and STV for enterococci) are regularly exceeded when no sewage contamination exists. In this study we found that concentrations of enterococci were elevated and did not meet the State recreational water quality standards at each site throughout the Kahaluʻu watershed. We also found high concentrations of Clostridum perfringens and molecular sewage markers (human-associated Bacteroides, human polyoma- and adenoviruses), which seems to infer not all indicator bacteria in the Kahaluʻu Lagoon and its watershed are from environmental sources. Cesspools, illegal cross-connections to storm drains, and possible leaking sewer lines are implicated as major contributors of sewage-borne microorganisms to the Kahaluʻu Stream; while leaking sewer lines and/or illegal crossconnections to storm drains are likely contributors of sewage-borne microorganism to the unnamed ditch that flows along Kamehameha Highway near the Kahaluʻu wastewater pumping station (WWPS). The Kahaluʻu WWPS does not appear to be contributing to the impairment of the lagoon. ‘Āhuimanu and Waiheʻe streams are less impacted by sewage than the Kahaluʻu Stream and the unnamed ditch, although some leaky sewer lines or illegal cross-connections may exist in the lower section of the ‘Āhuimanu Stream, and limited impact from cesspools and/or illegal cross-connections may exist in the Waiheʻe Stream. Cesspools are likely contributing to the impairment of Haiamoa Stream.

Groundwater Development Potential and Conceptual Hydrogeologic Model for Tutuila, American Samoa

Christopher K. Shuler, Paul R. Eyre, and Aly I. El-Kadi
May 2019, viii + 64 pp.


On Tutuila, the main island in the Territory of American Samoa, sustainable water resources management is a high priority. Groundwater provides drinking water to over 90% of the island’s residents. However the sustainability of this resource is threatened by overuse, salinization of wells, and reduction of water quality—potentially due to prevalent non-point pollution sources. Proposed solutions to these and other water issues on the island involve exploration for new groundwater sources with lower contamination potential and development of updated tools for management of existing resources. Both of these objectives benefit from an increased understanding of Tutuila’s subsurface structure and revisions to the conceptual hydrogeologic model of the island. In this report, currently available hydrological information was compiled with recently acquired subsurface datasets to inform an updated conceptual hydrogeological model of Tutuila’s groundwater and surface water resources. Published reports, recently collected data, and studies from similar basaltic islands were integrated to explain groundwater behavior in Tutuila’s already developed basal aquifers, and to inform hypotheses of high-level groundwater occurrence where data limitations exist. Datasets presented include borehole, geophysical, water level, aquifer test, geomorphologic, and surface water data.

To view the report click on: SR-2019-01

Groundwater Recharge for Tutuila, American Samoa Under Current and Projected Climate as Estimated with SWB2, a Soil Water Balance Model

Chris Shuler and Aly I. El-Kadi
2018, 42 pp.


Groundwater is the primary water source on the island Tutuila in American Samoa, and accurate quantification of groundwater availability is essential for well-informed management of this limited resource. A water budget approach using SWB2, a soil water-balance model was applied to Tutuila with the primary objective of calculating spatially and temporally distributed net-infiltration, which directly controls groundwater recharge rate. Other water budget components such as evapotranspiration, canopy interception, runoff, and mountain front recharge were also quantified with the SWB2 model for average present-day climate conditions. Additionally, the potential effects of future climate change on water resources availability were simulated by integrating dynamically downscaled climate predictions for 2080 to 2099 derived from externally supplied global climate model results. Notable improvements in this model over previously developed water budget models for Tutuila include flow-routing based on land topography, inclusion of the mountain front recharge process, and consideration of direct net infiltration from anthropogenic sources such as on-site wastewater units and leaking water delivery lines. Model results indicated approximately 54% of Tutuila’s rainfall infiltrates as groundwater recharge, 8% is lost to canopy evaporation, another 15% is lost to evapotranspiration from soils, and 21% is removed through surface-water features as stormflow-runoff. The model was able to simulate these processes with a high-spatial and temporal resolution with a 20 by 20 m grid-cell size, and a daily-resolution output time step. Climate scenarios suggested an increase in net-infiltration of 17 to 27% may be expected by the end of the century depending on the emissions scenario used.

To view the report click on:  SR-2018-04

Supplement to SR-2018-04
Management Summary

2020, 7 pp.

The primary goal for this study was to apply the Soil Water Balance 2 (SWB2) model to create high-resolution estimates of water balance components on Tutuila with a particular emphasis on groundwater recharge.

Provisional Hydrogeologic Data and Recommendations for Sustainable Groundwater Management, Tutuila American Samoa

Christopher K. Shuler and Aly I. El-Kadi
2018, 82 pp.


The main report provides a comprehensive summary of the currently available hydrogeologic information and data for American Samoa and then details and prioritizes the existing knowledge gaps that hinder progress towards a more water sustainable future. The report provides necessary background by covering the conceptual hydrogeologic model of the island and by presenting available recharge estimates. All available groundwater well data including average chloride concentrations (Cl-), drilling water levels, pumping water levels, well pump-rates, and values of aquifer specific capacity, transmissivity (T) and hydraulic conductivity (K) from aquifer tests is organized by wellfield and presented for all known current and historical wells on Tutuila. The report concludes by providing water management recommendations for groundwater use and development, aquifer testing, and for filling hydrogeologic data gaps.

To view the report click on:  SR-2018-03

Supplement to SR-2018-03
Management Summary

2020, 5 pp.

The purpose of this report is to support groundwater resource managers seeking to develop a groundwater sustainability plan for the island of Tutuila.

ASPA–UHWRRC Hydrologic Monitoring Network Handbook

Christopher K. Shuler and Aly I. El-Kadi
April 2018, 58 pp.


On Tutuila, American Samoa, weather monitoring and stream gauging operations were initiated by the United States Geological Survey (USGS) in the 1950s. However, as of 2008, all USGS monitoring activity on Tutuila had ceased. Although this legacy data remains as a valuable tool, climate change and variability continues to reduce its viability as time passes. Because this information is a critical component of sustainable water management, the University of Hawaii (UH) Water Resources Research Center (WRRC) and the territory’s sole water utility, American Samoa Power Authority (ASPA) have entered into a cooperative agreement for the purpose of developing a new weather station, stream gauging, and aquifer monitoring network. The instruments used in this network are intended to be simple, robust, and easily maintained to ensure longevity and continuity of data. Weather stations have been placed at pre-existing ASPA leased locations, and stream gauges are sited near roads, bridges, or previously gauged sites for ease of access and maintenance. Aquifer data is monitored at available locations within the existing ASPA well network. The goal of this project is to produce publicly available long-term hydrological datasets for use in water resource management or other applications.

To view the report click on:  SR-2018-02

Supplement to SR-2018-02
Management Summary

2020, 3 pp.

This document synthesizes the Hydrologic Monitoring Network Handbook produced as WRRC special report SR-2018-02, April 2018. The full report contains procedures for use and maintenance of instruments and overview information for all deployed equipment in the network.

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.


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.