MME Develops a Greenhouse Gas Emission Baseline for Wastewater Treatment Plant in Honolulu

When making decision about long-term capital investments, stakeholders typically consider traditional metrics, like cost and if the technology is validated in the industry. With building controversy regarding the effects of climate change and increased public interest in mitigation efforts in areas vulnerable to sea level rise, a new metric has emerged: greenhouse gas emissions.

The Sand Island Wastewater Treatment Plant in Honolulu, Hawaii.

The Sand Island Wastewater Treatment Plant in Honolulu, Hawaii.

This report was prepared to provide an analysis of potential secondary treatment options at the Sand Island Wastewater Treatment Plant (SIWWTP) in Honolulu, Hawaii, and a comparison between treatment levels and sustainability, with a focus on greenhouse gases. While the current federal administration has rolled-back progressive regulations on climate change and greenhouse gases, Hawaii is moving forward with the intention that climate change is not something political and must be addressed. Hawaii is especially vulnerable to the symptoms of a changing climate, including ocean warming and sea level rise. Per a 2018 Mayor’s Proclamation, Honolulu is committed to a 100 percent renewable energy future by 2045, which includes developing a community greenhouse gas inventory.

MME identified, assessed, and compared the carbon footprint of the existing baseline primary treatment facilities with the secondary treatment alternatives under consideration for implementation at the SIWWTP. The results helped to guide the selection of technologies for secondary treatment expansion of the plant, provide input on the selection of technologies for future process, and supported the environmental impact study.

This study used a design model run for the two secondary treatment options, step feed activated sludge (SFAS) and membrane bioreactor (MBR), based on the plant influent flow rate of 89 MGD.

The results showed that secondary treatment to the plant process will more than double the carbon emissions of the plant. Both the MBR and SFAS process require significantly more electricity than primary treatment only, resulting in additional emissions of almost 30,000 CO2e/yr., or approximately 40%.

One metric ton of CO2e is equivalent to the greenhouse gas emissions generated from driving 2,434 miles in an average car per year.

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These results provided a metric for evaluating secondary treatment options, beyond just cost. Additionally, GHG emissions are a common topic that broadens the audience beyond scientists and engineers and makes it accessible to the general public, giving them an understanding behind selection of technology at the plant.

The wastewater treatment industry is well positioned to lead the way in reducing GHG emissions because of the beneficial uses of biogas, which can be used for onsite production of renewable energy.

Further research and reporting will result in encouraging utilities towards using co-gen and becoming energy-independent. The benefits of this are two-fold. First, they are raising capital by not having to buy power and selling excess to the grid, and additionally they are offsetting the costs associated with emissions.

MME Leads Development of San Francisco's First Blue Roof at Fire Station 16

The seismic and related improvements for Fire Station 16, part of the Earthquake Safety and Emergency Response bond work, are now complete and the station is fully operational, with a ribbon cutting ceremony scheduled for Thursday, January 31st at 11:15 am.

The project included the demolition of the existing building, and construction of a new seismically safe fire station, which is designed to achieve LEED Gold rating. The building also includes the City’s first Blue Roof, a project spearheaded by MME.

MME led the development of the Stormwater Management Plan for Fire Station 16, and worked with the City and County of San Francisco’s Department of Public Works to identify the feasibility of a number of stormwater management alternatives for the project.  Various low impact design (LID) alternatives were considered for the land and roof constrained sight, and both a Blue Roof for detention and bioretention basins were selected. 

MME then facilitated the design to meet the SFPUC’s Stormwater Management Requirements for the City’s first Blue Roof stormwater management project. MME developed and submitted the Stormwater Management Plan and Stormwater Control Plan for the blue roof and bioretention, including a Maintenance Agreement for final SFPUC and Department of Building Inspection approval.  MME worked diligently with DPW and SFPUC to overcome schedule constraints, regulatory jurisdiction challenges, and overall design changes that occurred at various stages of the project and impacted stormwater management design.

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