Ecologically integrated water management: the Da Vinci challenge
Posted by George J Janczyn on March 21, 2011
(Norman Allenby wrote this guest column)
Leonardo Da Vinci had a relevant thought on this subject. His Ideal City postulate #6 states, “ Require that each house have its own sewerage system and be built on aesthetic and environmental principles with access at ground level.” The Da Vinci challenge is to design such a system, not just for homes, but buildings, subdivisions, shopping centers and micro watersheds that comprise greater San Diego. Homes, buildings, subdivisions, shopping centers are all parts of our urban water shed. They each take in water and give back wastewater. With each having its “own sewerage system,” the Da Vinci challenge would be met and the opportunity for onsite recycling created.
Under our present integrated water management system there is insufficient recognition of the potential for on site reuse of water. We have done a great job in corralling water from Imperial County to augment waters received from the Metropolitan Water District. We largely ignore storm water allowing it to contaminate our beaches. We discharge 180 MGD of wastewater into the Pacific Ocean at our Point Loma treatment facility. We continue to delay the intended use of the North County reclamation plant’s reclaimed water, augmenting San Vicente reservoir. We do distribute a modest amount of reclaimed water for irrigation through our purple pipe system, but our wastewater is largely wasted. That waste can be avoided through an ecological approach to water management.
Ecologically integrated water management utilizes process water, storm water and “waste water”. It first calculates how much water a facility needs, how much storm water is site available and how much “waste water” is site available. Any deficit between site available water and needs is met by process water purchased from the local provider. The focus of ecological water management is conservation and reuse and, yes, more reuse.
In our homes and places of work we presently buy whatever potable water we desire. We drink, if we are conscientious, maybe eight glasses a day. Of the 200 to 400 gallons a household may use, most of it goes down the drain. Once down the drain, that water becomes wasted, through our wastewater facilities. Storm water is directed to streets. The simplest effort of capturing storm water in a cistern for future use is assiduously avoided. That too is wasted. The same is true in urban structures, our schools, office buildings and shopping malls. Our urban watersheds waste wastewater.
There is really very little water used in our homes, rather water is transformed or contaminated. It becomes part of human tissues and plant tissues. Some evaporates. It is contaminated in kitchens, bathrooms, and laundries. Could we remove contaminants from the water or not put them in the water in the first place? Could we create a water cycle that is integral to the home by cleaning the waste water on site and reusing it?
By using composting toilets, a major contaminant of urban wastewater could be avoided and used as compost. Urine separating toilets salvage another valuable asset, urea, to be combined with gray water. By minimizing or eliminating the garbage disposal additional contamination, ground up animal and vegetable waste is avoided. Those materials should be composted. By using bio degradable soaps and detergents additional contamination could be avoided. By filtering laundry water laundry related contaminants can be removed. With those few steps, the resulting waste water would likely be a reasonably treatable shade of gray suitable for reuse on site. With disinfectant ultraviolet, the water reuse potential would be enhanced. As a minimum irrigation, toilet flushing, air conditioning, ground discharge and reservoir or stream augmentation are possibilities. Indeed treated gray water might be stored in cisterns for future use.
A fundamental measurement of water is the acre foot, sufficient water to cover an acre of land with a foot of water. An acre foot equals 326,000 gallons and supports two households for a year, roughly 400 gallons of water per day. That 400 gallons is potable water.
Let’s then ask the ecological question how much potable water do we need? Do we need potable water for irrigation? Do we need potable water for flushing? Do we need potable water for showers and sinks? Do we need potable water for laundry? Do we need potable water for dishwashers? We do need potable water for food and drinking. Choose your pie chart, but clearly irrigation and toilet flushing do not require potable water. The point is that we don’t need 400 gallons of potable water allocated to us per household per day. We can use recycled water, disinfected or not for lots of different purposes, so do the math and design the quality and quantity of water to meet the water needs of the individual household, structure or structures. There is sufficient data to standardize designs. The occasional storm water dividend can be added to the supply. The Da Vinci challenge, again, is to design the system.
With ecological engineering the Da Vinci challenge could be met. There exist zero discharge systems. These systems use up kitchen sink and toilet water literally throwing it away, but that is not what we want in drought country. The gray water systems take shower, sink, dishwasher, and laundry water and use it for irrigation, toilet flushing or air conditioning. These same waters can be disinfected with ultraviolet and made potable with small reverse osmosis (R/O) systems similar to those used on yachts and sailboats. Storm water can be collected and used to augment the water sources for these systems These same systems can be scaled up or down to meet the needs of a home, building, subdivision, shopping center or micro watershed.
These natural systems have the capacity of greatly enhancing our water independence. For every gallon reused/recycled not only is the gallon saved, but the energy in bringing the gallon to the site is saved, two dividends. The third dividend is energy not spent in removing the “wastewater” to our sewer system. Leonardo Da Vinci would be pleased were we to recognize and use these systems.
The Rocky Mountain Institute asks the question, “How much of the infrastructure that defines ‘modern’ development is already obsolete? ” Two items it identifies as obsolete are “central potable-water provision” and “central sewerage and chemical-engineering based wastewater treatment.” Those essentially are our existing systems. For water it suggests, “Water: roof catchment, storage efficiency.” On sanitation it suggests, “onsite (composters, digesters Swedish/German urine-separating toilets, …), low/no water use nutrient recovery,” and lastly it suggests, “Storm water: landscape-based management.” See http://www.rmi.org.
Natural Capitalism, Chapter 11, is entitled “Aqueous Solutions”. There identified are several of our perennial problems along with solutions. John Todd’s “Living Machines” is identified is a valuable tool, a major source of system efficiency. It observes , “A biological treatment plant costs about the same or less to construct, especially for small-capacity systems. It yields valuable fertilizers and soil amendments instead of toxic chemical hazards, looks like a water garden, greenhouse or wetland, doesn’t smell bad and yields safer, higher-quality water.” Versions of these systems have been up and operating in Canada and New England for more than a decade. They return as tertiary or advanced secondary ninety percent (90 %) of the water processed for a multitude of reuses, toilet flushing, hydroponics, greenhouse, fish, wetlands and irrigation. To come full circle, as most water does, we have for the asking the answer to the Da Vinci challenge.
There are four companies that do this on-site waste water treatment, Ecotek in Vancouver (http://www.ecotek.ca), Ecological Engineering Group (http://www.ecological-engineering.com), John Todd Ecological Design (http://www.toddecological.com), and Worrel Water Technologies (http://www.worrelwater.com). We are not talking septic tanks.
Ecotek suggests that the tertiary water, the general level of water quality produced by these systems, is suitable for hydroponics and fish growing in addition to the toilet flushing, landscape irrigation, and air conditioning. They also tap into existing sewer lines for a waste water source which they clean up and reuse on site. These are all largely design build firms which endeavor to meet the design criteria including water quality called for by the governing authority. Ecological Engineering Group and its predecessor had many demonstration facilities and have two operating plants, one at Weston, Mass. and the other at Ipswich, Mass. John Todd’s organization has done work in China and South America. Worrel seems to focus on the use of large septic tanks using the effluent to create a wetland environment. Ecological Engineering keeps solids in suspension allowing microorganisms to consume the solids before moving into the sub surface wetland. The next step is to place a bio-digester adjacent to the on-site waste water plant using the sludge and its energy to run the facility. That step has not been taken to my knowledge.
Applying this technology to our existing systems gives us the ability to tap into the existing sewer system for waste water, doing away with the purple pipe system. It also gives us the ability to have new development reuse its own waste water rather than shipping it the coast for export to sea. Working back from the outer limits of our waste water system, uphill and inland from the Point Loma facility, we have the ability to begin to reuse the water we are now throwing away working back to the coast until we have reused all the waste water and there is no more to be wasted. It also suggests that we need to think of a decentralized approach to our water use and reuse. Were we to recycle and keep all the water in our systems cycling while capturing our storm water year after year we would reduce our need to buy water from MWD et.al.
Norman R. Allenby
Onsite Water Treatment, Inc.
Licensee of Ecological Engineering Group, LLC and Ecocyclet, LLC
Telephone: 619 301-9059