Business Agenda Item 4b
STAFF REPORT
City Council Business Agenda Item
DATE: September 18, 2023
TO: Honorable Mayor and Council Members
FROM: Christopher Christianson, Chief Treatment Plant Operator THROUGH: Merritt Perry, City Manager
SUBJECT: Authorize the Purchase of a Magnesium Hydroxide Tank and Feed System, Resolution 2023-28
STAFF RECOMMENDATION:
Authorize the purchase of a magnesium hydroxide tank and feed system for the wastewater treatment plant, in an amount not to exceed $60,000.00, by adopting Resolution 2023-28.
EXECUTIVE SUMMARY:
Natural, biological processes that are part of the City’s wastewater treatment plant cause a significant drop in pH and alkalinity. To maintain neutral pH conditions for the City’s treated effluent, and thus avoid potential effluent violations, staff have historically used sodium hydroxide (caustic soda) as a pH buffering agent. Sodium hydroxide is a hazardous chemical, and as such its use at the plant has many drawbacks, including:
Safety hazard to staff. It will burn skin and eyes on contact, and regular personal protective equipment and caution is required to work safely with the chemical. Very corrosive. Small leaks of sodium hydroxide can cause damage to nearby concrete and buildings, requiring regular corrective maintenance. High freezing threshold (60˚F). The shed requires constant heating with energy intensive space heaters.
Toxic if overfed to plant. If accidentally overfed, the microorganisms in the aeration basins will die, which can result in a treatment disruption and subsequent effluent violations.
High sodium. It adds extra sodium to the treatment process, elevating total dissolved solids (TDS) in the effluent. TDS is a constituent of concern in receiving waters.
Recognizing the drawbacks of sodium hydroxide, but also the reality that pH buffering is required as part of the City’s treatment process, staff began to research alternative methods for pH buffering in 2022. The most promising alternative to caustic soda staff identified is magnesium hydroxide.
This chemical supplies the necessary buffering capacity required in the aeration basins without the downsides:
Safe. It is nonhazardous and noncorrosive. It will not burn skin and eyes on contact. Lower freezing threshold (32˚F). This will significantly reduce the level of electrical heating currently in use for caustic soda.
Business Agenda Item 4b
Nontoxic. If accidentally overfed, the pH will not spike to as high a level as caustic, and thus the microorganisms in the aeration basins will survive. Less sodium. It will not add extensive TDS discharge levels like caustic. Improves settling. Magnesium hydroxide also acts as a coagulant that can improve performance in downstream treatment processes.
In addition to the considerations above, the cost of magnesium hydroxide is also more economical than caustic soda. Currently, magnesium hydroxide is approximately 20% cheaper, magnesium hydroxide is also a more effective pH buffer, and thus 40% less chemical is required to achieve the same buffering effect.
With the above considerations in mind, staff began an extended trial with magnesium hydroxide in June 2022 using a demonstration system that was provided by the chemical supply company.
Over the past year-plus, staff have found that the new chemical has proven very reliable, safe, and efficient. Additionally, staff estimate that over the past year the City has saved approximately $40,000 compared to if the City had continued using sodium hydroxide.
With the trial period over and the supply company needing their equipment returned, the City is now faced with the decision to go back to sodium hydroxide, or invest in the equipment required to use magnesium hydroxide from here forward. Given the cost savings, in addition to the highly improved safety and maintenance considerations noted above, staff are recommending that the City switch over to magnesium hydroxide long-term. Staff included budget in the 2023-24 fiscal year budget to cover the cost of the switchover.
Earlier this fiscal year staff began soliciting quotes for a new, 5,000-gallon magnesium hydroxide tank and feed system. This larger tank (larger than the temporary system used over the past year) will mean fewer deliveries per year, which will also save on costs. The City received preliminary quotes, which are still being finalized, and the current estimated cost range is approximately $50,000 - $55,000. As noted further below, staff are seeking approval to award a contract of up to $60,000, and staff would work to finalize quotes after approval and ultimately purchase the system from the lowest responsive bidder.
All quotes for the magnesium hydroxide system were greater than City purchasing limits, as detailed in Fortuna Municipal Code Chapter 2.50.040, which require a formal bidding process.
Staff is requesting that the Council make an exception to formal bidding, according to Section
2.50.070, by finding that the purchasing of the magnesium hydroxide system with the lowest quote is in the City’s best interest. It is staff’s recommendation, based on the information included above, that this purchase is in the best interest of the City, and that formally bidding the purchase is only likely to add cost to the overall procurement of the materials (bonding, advertising, etc.).
Additionally, the use of a pH buffering agent increases during the winter time, and therefore it is in the best interest for the City to have this system installed as soon as possible. Formal bidding the purchase and developing a bid package would be anticipated to add 4-6 weeks to the procurement timeline for the equipment, and therefore would put the City in a more difficult situation with equipment startup should we experience an early winter. Purchasing through quotes would allow staff to initiate the purchase process immediately.
FINANCIAL IMPACT:
This project is included in the 2023-2024 wastewater treatment division capital outlay budget in the amount of $75,000 (wastewater enterprise budget). As mentioned above, staff anticipate that Business Agenda Item 4b
the total project cost will be approximately $50,000 - $55,000, and therefore staff are requesting that the council authorize a purchase amount of up to $60,000.
Converting the existing caustic soda feed system and purchasing the magnesium hydroxide tank and feed system should result in an overall savings for the City. Magnesium hydroxide costs less than caustic soda, and because of its chemical properties, it is also a stronger buffering agent. The City will use less magnesium hydroxide than caustic soda, and at a far lower cost. As noted above, staff anticipate that over the past year the City has saved approximately $40,000, which equates to a simple payback period for the entire system at just one-to two years.
RECOMMENDED COUNCIL ACTION:
1. Receive staff presentation and review Council questions with staff
2. Open Public Comment
3. Close Public Comment
4. Motion adopt Resolution 2023-28 and read by title only. Voice vote.
ATTACHMENTS:
Attachment A – Resolution 2023-28