Agenda - Council - 03/10/2015 - Laserfiche WebLink

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anaerobic digestion to reduce biosolids volume prior to its agricultural use and to produce biogas (methane) for in -plant uses. Energy. In addition to generating energy from processing biosolids, energy conservation has been, and continues to be, implemented through wastewater treatment process selection and performance optimization, installation of higher efficiency equipment and lighting, and reducing building energy use. Purchase of power from solar power generation facilities co -located at major treatment plants is also being pursued. Additional technologies, such as fuel cells, will be pursued as their capabilities and economics are proven. Wastewater Reuse Injecting highly treated wastewater into aquifers has potential to supplement groundwater and surface water as sources of water. Year-round reuse of wastewater could include recharging groundwater, industrial cooling, and use as nonpotable water. ("Potable" water is water suitable for drinking.) Seasonal possibilities include irrigation of agricultural land, golf courses, parks, and lawns. Each type of use has water quality requirements that may require additional wastewater treatment before it is distributed and used. Wastewater reuse challenges include: Groundwater Recharge. Groundwater recharge with treated wastewater is typically implemented in limited areas (sites). Few areas have high soil permeability allowing treated wastewater to seep into the groundwater and depth to groundwater that is shallow enough for it to disperse into the groundwater. Industrial and Irrigation Uses. Water softeners that are used to remove hardness from groundwater (which is the primary water source for communities outside the urban core) introduce high salt content into water/wastewater. The salt content makes the water undesirable for industrial uses (it corrodes cooling water systems) and irrigation uses (salt buildup can limit plant productivity). Wastewater treatment with reverse osmosis to remove salts is very costly, and requires a method - for example, evaporation, which is very expensive - to dispose of the brine. Metro area industries have generally been successful with their own water conservation and re- use programs. There are very few high-volume industrial users of reused wastewater. Wastewater uses for irrigation are highly dispersed and seasonal, and account for approximately 20% to 30% of total water use. Nonpotable Water. Potable water uses include drinking, bathing/showering, food preparation, dish washing, and clothes washing. Toilet flushing is a significant nonpotable water use, estimated at 20% of total water use. Implementing a nonpotable water use system would require separate water distribution and plumbing systems. Inherent challenges are cost, the typical development/financing process (and associated competition), regulatory requirements, institutional arrangements, and public perception. The Council will consider wastewater reuse as part of its regional planning for water supply. For example, wastewater reuse for toilet flushing and irrigation could reduce groundwater demand to serve growth. 42