20,000,000 passengers per year fly over the 12 giant anaerobic digester eggs of Boston’s Deer Island. In April 2020, thousands of the world leaders in filtration will visit San Diego, 30 miles South of the Western Hemisphere’s largest desalination plant which provides water to the hotels and beaches that they’ll visit. Nearly 3,000 miles apart these two plants show the diversity of municipal water needs, the economics of water investment, the role of geography and rain fall, and how technology drives water supply and demand.
Deer Island is designed to process waste water and release it far off shore. The Boston metropolitan area has sufficient water supply – the challenge is handling storm water run off in a way that does not pollute the harbors, bays and surrounding wildlife. To halt 10 billion gallons of annual pollution overflow into the bay, nearly $4 billion has been invested by the Massachussetts Water Resource Authority (“MWRA”) to be able to process up to 470 billion gallons of waste per year. Like a mall parking lot designed for the Christmas season – Deer Island must be able to handle flows on the highest days and anticipated future growth.
Carlsbad provides a very different story – at a cost of nearly $1 billion, the desalination plant is capable of processing up to 18 billion gallons per year. About 80% of that water volume is purchased by San Diego, providing 7% of the city’s water needs. The city pays a premium for the security of water supply – on a per acre foot basis, Carlsbad compares well to its competition, but is not cheap:
- $2500 – Cost to import water from other areas in CA
- $2200 – Cost of Carslbad water
- $2000 – Cost of recycled / re-used water (water re-use is the future)
- $1200 – Area reservoir water
- $700 – Upstream access when possible
San Diego chose water security over water cost – a wise decision based on the volatility of water rights and access in the Colorado River basin.
Drivers in Water Investment
These plants represent nearly $5 billion in investment in two very different water situations with very different regional needs.
Boston’s Deer Island: Hygiene, Disease and Growth
Boston’s harbor has been the source of constant investment since settlement. Dams were built causing sewage to foul the bay. Million dollar homes cannot look out on raw sewage and smell of the same. Boston’s investment in Deer Island is a long term commitment to managing the city’s hygiene, controlling for disease outbreak, and is ultimately an investment in the area’s future growth.
San Diego: Water Security
Reisner’s Cadillac Desert – the most well known book on water planning – takes place on the Colorado River, the same river on which provides San Diego with water. The Colorado no longer reaches the sea – with upstream water rights, ranching, and agricultural diversions robbing it of the needed flow. In years with low rainfall, San Diego does not have sufficient water.
Investing in the plant put San Diego at the front of the learning curve about how RO and desal can be implemented in the US, and there are already plans for a sister plant further North in Huntington Beach to service Los Angeles. By investing in this technology, San Diego is in a better situation to negotiate with other sources of water, and to understand how the cost of water can be impacted by technology.
Size, Impact and Investment
Mankind creates about 330 km^3 of wastewater per year, and converts over 50 km^3 of saltwater to fresh water via desalination. [Source: Global Fluid Volumes] This puts the 1.7 km^3 (0.5%) max treatment capability of Deer Island and 0.7 km^3 (1.4%) desalination capacity of Carlsbad in context.
Reversing those numbers, we can start to see the scale of investment required:
- $4 Bn / 1.7 km^3 (0.5%) * 330 km^3 = $800 billion to treat all global waste.
- $1 Bn / 0.7 km^3 (1.4%) * 50 km^3 = +$70 billion to recreate current global desalination infrastructure