Tannins in drinking water are caused by natural decaying of organic matter. Leaves or pine needles in the gutters are generally the cause in a rainwater collection system. A faint yellowing of water generally occurs at .5 parts per million or PPMs with .5 – 2.0 PPMs looking like the color of ginger ale, and 3.0 – 5.0 PPMs would take on the appearance of dark tea. The tannins may cause a yellow color of the water, yellow staining on fixtures, and yellow staining in laundry.
Although aesthetically displeasing, tannins generally pose no real health risk, but may affect the performance of the UV system by not allowing the UV light to penetrate thoroughly through the water column.
Therefore, it is very important to minimize tannins before storage of collected rainwater. Organic matter must be kept from accumulating in gutters, down spouts, and screen baskets. Gutter screens are an effective method of prevention of organics in gutters and down spouts. Both gutter screens and screen baskets should be inspected and cleaned as needed to prevent tannins from occurring. Since the discoloration is in solution, removal can be difficult and expensive. Ozone, ion exchange, and activated carbon can help with removal of tannins to some degree. If you do end up with tannins in your water, it is best to drain the cisterns, rinse and start collection again, however the best solution is diligence in maintenance.
Lights partly powered by drinking water?
As infrastructure ages, clever solutions are being invented to create sustainable energy systems. A new method adopted in Portland, OR captures energy as water flows through the city’s pipes, creating hydropower without the negative environmental effects.
According to an article in Fast Company, small turbines in the pipes spin in the flowing water, sending that energy into a generator. The power is sent into the grid, and although it isn’t enough energy to run a city, the pipes could potentially power individual buildings like a library or school, or help offset an energy bill. An interesting feature is that the system can generate electricity at any time of day, regardless of weather, since water is always flowing through the pipes.
Greater potential may be California, where a large chunk of energy usage goes into the water supply. With these pipes, utilities might generate some of their own much-needed power.
Click here to read the full article.
Portland and Mt. Hood from Wikimedia Commons, the free media repository courtesy of Amateria1121
UV disinfection is the most common method used in residential rainwater collection systems.
UV light is generated by supplying voltage across a mixture of gas, causing a discharge of photons, disrupting the DNA of microorganisms which prevents them from reproducing. If the microorganism cannot replicate, it cannot infect, so viruses, bacteria, Cryptosporidium and Giardia cyst threats are effectively reduced.
A residential UV system typically consists of a power supply (ballast), a UV lamp housed in a Quartz sleeve inside a stainless steel chamber. The flow is directed close to the UV light while passing through the chamber. Effects of turbidity or clarity of the water before entering the chamber must be reduced by proper filtration upstream. Sediment and carbon filtration is used to reduce solids and solution contaminants, which can reduce the effects of UV disinfection. Filtration and UV bulb most be routinely changed in order for all to work effectively. It is recommended to follow manufacturer’s instructions closely, and filters should be changed out as needed.
Some UV systems offer an alarm or sensor with solenoid shut down if the UV system is not working properly. A class “A” UV is the only system considered to purify water that has NOT been deemed “safe to drink”, therefore caution is recommended in the use of a class “B” filter which maybe more tempting to use because of price. The difference between the two is the dosage of the UV light; the lower dose is not as effective in disinfecting. If a more advanced filtration system is used prior to disinfection, you can increase the effectiveness of the class “B”, but caution must be taken for proper results.
UV disinfection provides a relatively low cost, dependable, efficient, chemical free method of water purification that the homeowner can operate to disinfect his or her water supply.
With proper design, installation, and maintenance, clean, safe, and dependable potable water can be achieved from UV disinfection and rainwater collection.