The Right Water for the Right Purpose

Water development and supply in the United States have historically been based on four overriding considerations and assumptions.  Urban water and resource management have been defined by the following four operating philosophies - -

1. Water Supply Considerations - - Remote sources of supply.  A lack of pollution-control systems and technologies, local water supplies inevitably became polluted.  It impossible to produce safe drinking water in sufficient quantities.  Remote resources of water were required to be imported.
2. Optimizing Around Cost and Efficiency - - Development of water resources were optimized around the cost of the infrastructure.  With abundant water resources and cheap energy, the least expensive systems were those that optimized infrastructure costs.
3. Functions - - Single purpose systems for drinking water, storm water, and used water.  The water in my toilet bowl came from East Texas and is treated to a drinking water standard.  When water has low economic value and energy is cheap - - one can pee into their drinking water.
4. Configuration Management - - Centralized systems that either import water or export wastewater, driven by economies of scale that assume abundant supplies and cheap energy.

Look for water infrastructure systems in the near future to "evolve" as the new constraints of water availability, higher energy costs, and changing social norms drive the new economic realities of water resources.  Consider a future where:

1. Water Supply Considerations - - Local actions and forces become increasingly critical.  Locally collected rainwater ("rainwater harvesting") and used water for reclamation and reuse becomes a critical part of the equation.
2. Optimizing Around Cost and Efficiency - - We start to price water in the context of its economic value in an era of increasing energy costs.  Optimization evolves toward utilization optimization and energy conservation.
3. Functions - - Multipurpose systems to integrate functions.  Technology allows for a greater utilization of the waste streams.  The focus becomes a policy execution driven by "The Right Water for the Right Purpose."
4. Configuration Management- - Hybrid systems that include both centralized and decentralized components.  Decentralization strategies include "green" storm water systems (three rules of storm water - - infiltrate, infiltrate, and infiltrate), used-water reclamation/reuse systems, and in-home treatment.

The future for water resource engineers may be marked by designing and managing water from the standpoint of utilizing "The Right Water for the Right Purpose."  Separate but not equal water systems may become the norm.  A relatively small volume of water (approximately 40 liters per person per day), is needed for direct consumption - - a much larger volume of water, ranging form 100 to 400 liters per person per day is used for laundry, toilet flushing, bathing, and outdoor water use.

From a wastewater standpoint, we will have to start thinking in terms of "grey", "black", and "yellow" wastewater.  Segregation allows for thinking more deeply about "The Right Water for the Right Purpose."  What non-portable uses are most appropriate for grey water?  How much energy is available in "black" water from the organic material?  Yellow water contains unused pharmaceuticals and hormones - - what are the beneficial impacts to society of segregating "yellow" water?  Between my hot bath and dish washer - - how much thermal energy is available in the wastewater as it departs my house?

Dual-flush toilet systems are another example of finding "The Right Water for the Right Purpose."  Two buttons that have two different volumes of water for two different waste streams - - one button for "black" water and another button (with a lower volume of water) for "yellow" water (some concern has been raised regarding maintenance problems in the case of pushing the incorrect button - - maybe some type of national infomercial during American Idol would help the button challenged). 

Remember, "The Right Water for the Right Purpose" produces huge challenges, but it also produces huge opportunities in a world of increasing concerns associated with water sustainability.