Summary of Project Merits
The ASCE 2019 Report Card estimated Hawai‘i requires $2.2 billion in wastewater infrastructure spending to meet its wastewater management needs of safeguarding public health and the valuable Hawai‘i environment.
In 2021 the County of Kaua‘i (County) completed a rigorous project focused on improving the wastewater effluent quality at Waimea Wastewater Treatment Plant (WWTP) to generate R-1 recycled water for irrigation purposes, with a minimal $30,000 capital investment. By leveraging the collective team’s understanding of the WWTP, project goals were met by achieving Hawai‘i’s regulatory requirements for R-1 recycled water. Expensive infrastructure construction was avoided by making simple adjustments to treatment processes driven by wastewater testing data. The project will result in the preservation of groundwater for potable use, as well as the reduction of injection wells used for wastewater effluent disposal.
Minimizing Costs and Maximizing Benefits for the Community
We see water all around us in Hawai‘i, especially on the majestic valley isle, Kaua‘i – one of the wettest places on earth. Regardless of how plentiful water is in Kaua‘i, the cost to deliver safe drinking water constantly increases and challenges the environment. This project was the first step for the County to future-proofing its water system. By improving existing systems and treatment processes at Waimea WWTP, the community benefits in the following ways:
• Generation of recycled water in Waimea Town for irrigation
• Decrease of potable water used for irrigation and thereby preserving resources
• Avoided expensive infrastructure construction
• Reduced energy, operational, and chemical costs at the WWTP
• Minimized the environmental impact caused by improvements
Using Existing Resources for a Better Solution
The County faces many challenges as noted in the ASCE 2019 Report Card, such as a lack of funding to effectively maintain and improve existing infrastructure systems. Capitalizing on existing resources proved to be the most valuable for this project.
Testing and analyses of wastewater were initially performed to inform which processes could be improved and guide how to minimize major repairs and improvements. The County leveraged its own staff to conduct most of the testing, analyses, and construction which reduced costs.
Instead of resorting to a common design-bid-build method, the project’s approach included workshops with the operators to facilitate open discussions regarding design concepts. The project’s success depended on the operators’ input regarding lessons learned to reach solutions. Using operating and engineering expertise in a collaborative way minimized challenges and costs for efficient decision-making.
Interactive, Collaborative, Data-Driven Decision-Making
1. Interactive Workshops – Operators provided feedback to KJ’s engineering team on potential treatment
process improvements.
2. Data-Driven Decisions – Operators and engineers collectively reviewed wastewater testing data to decide on a course of action. Operators implemented improvements over a couple of weeks and used data from wastewater analyses to adjust treatment processes as needed.
3. Collaboration – The team reviewed the wastewater testing results together to collaboratively develop the next step. Step 1 was repeated until the wastewater effluent met regulatory requirements for R-1recycled water.
The project utilized data, workshops, and collaboration to optimize the use of existing infrastructure to minimize costs, effort and time.
These steps helped to confirm the treatment processes were performing at their best before attempting major replacement or rehabilitation construction – an outstanding example of reliability-centered design. This project optimized existing infrastructure which minimized time, effort, and cost.
Success with Minimal Construction
Improvements were focused on ones that could be completed without construction or constructed by the County’s in-house team of operators, mechanics, and electricians.
The improvements included:
• Using only one out of the two existing flow equalization tanks (FETs), as well as turning off the aeration system, to preserve 5-day biochemical oxygen demand (BOD5) for microorganisms present in the downstream
biological process
• Installing a mechanical mixing system to increase polymer conditioning for better flocculation of solids and reduce the amount of polymer used, resulting in savings on polymer costs
• Installing a chlorination dosing system to prevent biological growth on the disk filters
After project completion, the WWTP successfully and reliably met the R-1 recycled water turbidity and filtration requirements.
Efficient Improvements Creates Savings for the Community and Environment
By avoiding the construction of large expensive upgrades, such as a new treatment process or replacing equipment, the County not only saved the community money and time but prevented environmental impacts often associated with construction activities, such as landfill waste, energy consumption, and disturbances to the surrounding natural environment. Additionally, the outcome of the project saves energy, operational and chemical costs, and preserves groundwater resources.