This invention relates to the field of systems for treating potable water in municipal and similar distribution lines to reduce and remove undesirable disinfectant byproducts from the water.
Potable bodies of water and in particular municipal and other water sources intended for drinking are commonly treated with disinfectants such as chlorine and chloramines. These disinfectants very efficiently and effectively eliminate harmful agents in the water making the water potable and suitable for drinking. However, such disinfectants can and usually do create undesirable disinfectant byproducts such as chloroform, bromodichloromethane, dibromochloromethane, and bromoform which are all forms of trihalomethanes (THM). In very small amounts (e.g., very low parts per billion), these THM are not believed to be a serious threat to health but reduction of them in potable water tanks or reservoirs such as municipal water systems is always desirable and is increasingly being mandated by law.
An effective way of removing THM from treated water is by air stripping. The basic operation of air stripping is that upon contact with air, the THM in a liquid or aqueous state in the treated water will volatilize to a gaseous state and can then be removed with the air (i.e., stripped from the water) leaving the water safer to drink. The THM in this regard have a relatively high vapor pressure while having low aqueous solubility which enables such stripping methods to be effective. One such method involves bubbling air into a tank of water at various depths and letting the air bubbles contact and volatilize the THM which then rises to the surface with the air and into the atmosphere. Bubbling air into the tank water can be somewhat inefficient as it is often the case that the tank water needs to be passed several times through the bubbling or treatment zone to ensure adequate contact of the air with the THM in the water. Dead or uncirculating spots can also develop in the water in the tank that go untreated, particularly in a large tank (e.g., 20-35 feet high and 30-100 feet wide holding 150,000 to 2,000,000 or more gallons). The equipment and operational costs of such bubbling methods can also be relatively high particularly if the air is introduced near the bottom of the tank through air diffusers with a relatively large footprint. Such depths require that the air be raised to a relatively high pressure before it can be introduced into the water.
Another method of air stripping involves spraying or atomizing the water held in the tank into the headspace or air gap region between the surface of the tank water and the ceiling of the tank. This method requires that great quantities of fresh air be constantly circulated through the headspace and often requires powered blowers to do it. Otherwise, the fresh air volume may be insufficient for thorough treatment and the air in the tank may actually become saturated with THM that may then undesirably condense and return to the water. The process of volatilizing the THM by air contact also consumes heat from the air and water and if the ambient air flow is not sufficiently refreshed, the temperature of the air and water in the tank may drop to the point that the efficiency and effectiveness of the THM volatilization process may also significantly drop Further, in large as well as small tanks, the problem still can exist that dead or uncirculating spots can develop in the water in the tank that go untreated. The same water may then end up being treated over and over again while much is missed. Additionally and unless there is a very efficient and effective circulation in the tank, water entering it may end up leaving it and being put into the municipal distribution system without being treated. The same is true for the bubbling method discussed above.
With this and other problems in mind, the present invention was developed. In it, a treatment unit is provided that has been specifically designed to be portable and deployable (e.g., plumbed) wherever needed or desirable along a municipal or similar water line to treat and remove undesirable disinfectant byproducts such as THM in the water. Such deployment can be as a result of any number of situations where higher than desirable levels of such byproducts may exist or be detected in the water line. Such occurrences can result for example from a less than complete removal of the THM in the upstream, main treatment tank(s) or as a result of a boost or secondary treatment of the water with disinfectant (e.g., chlorine) downstream of the main treatment tank(s) that may be needed or desirable in areas along the distribution line. The unit of the present invention also effectively treats virtually all of the water passing through it and avoids the need to have an internal circulation system to ensure complete treatment of all of the incoming water.
This invention involves a portable unit for treating potable water in municipal and similar water lines to reduce and remove undesirable disinfectant byproducts such as trihalomethanes from the water. The unit has a housing with water and air inlet and outlet arrangements. The water inlet arraignment includes a pipe section connectable to the municipal water line at a first upstream location to deliver water from the line into the housing. The incoming water laden with THM in liquid state is then sprayed substantially horizontally into the main body of the housing through at least one nozzle along a duct or chamber through a perforated splash screen and up against a splash plate. The splash plate subsequently diverts or redirects the water spray laterally outwardly, backwardly, and downwardly onto an inclined ramp. The inclined ramp then guides and directs the water downwardly into the lower part of the housing where it is collected or held until it is pumped back into the municipal water line.
The air inlet arrangement of the housing includes a filter through which ambient air is drawn into the duct or chamber by the nozzle spray and mixes with the sprayed water as it travels along the duct through the splash screen to strike and be diverted by the splash plate onto the inclined ramp. As the air contacts and mixes with the sprayed water, it volatizes the THM in liquid state in the water into a gaseous state. The mixed air and gaseous THM are then driven out of the housing through a discharge duct or vent into the ambient air surrounding the housing. In an efficient manner, the driving force to draw the air into the housing and drive the mixed air and gaseous THM out of the housing is completely provided by the water pressure in the municipal water line.
In operation, the treatment unit of the present invention is self regulating and beneficially operates in at least two modes automatically. In a first mode, substantially all of the flow in the upstream municipal water line passes through the housing to be treated. This will occur when the fluctuating flow rate in the municipal pipeline is substantially equal to or less than the discharge rate of the unit's pumping arrangement. Virtually all of the pipeline water then passes through the housing and is treated. In a second or safety mode such as when an emergency (e.g., fire) may exist downstream of the unit and the need or demand for water exceeds the treatment capacity of the unit, the operation is modified. More specifically and in the second mode, the unit continues to treat water up to its capacity but the remaining portion of the pipeline water exceeding this capacity bypasses the unit and goes directly downstream. The treatment unit then presents no impediment to the safe delivery of the maximum amount of water downstream to fight the fire or meet some other emergency or need. Whether the treatment unit is operated in its first or second mode is then automatically determined by the flow rate in the municipal pipeline as determined by the fluctuating downstream demand.
The portable treatment unit or apparatus 1 of the present invention is shown in the exterior views of
The unit 1 includes the exterior housing 3 of
The water inlet arrangement of the housing 3 as schematically shown in
The main purpose of the portable unit 1 as discussed above is to treat the incoming water from the municipal pipe line 2 and remove undesirable disinfectant byproducts such trihalomethanes (THM) from the water. To accomplish this, the housing 3 of the treatment unit 1 is provided with an air inlet arrangement to mix ambient air 8 in
To aid in this process, the splash screen 15 (see
The housing 3 as illustrated in
Primarily for safety purposes, the open and upwardly inclined sheet 47 and drain 49 on the left in
The water outlet arrangement of the housing 3 further includes at least one pump 53 in
In operation, the treatment unit or apparatus 1 is self-regulating and beneficially operates in at least two modes automatically. In a first mode, substantially all of the flow in the upstream municipal water line 2 in
The relative length and location of the open bypass section 2″ can vary as desired as illustrated in a comparison of
Although the pressure in most municipal pipelines like 2,2′ is normally fairly constant (e.g., 60 psi above atmospheric plus or minus 5 psi), the flow rate through the municipal line typically can fluctuate widely during the day and seasonally depending upon the downstream demand. For instance, it is common to see daily peak demands between 5-9 am in the morning and 5-9 pm in the evening. It is also common to see higher demand in the summer and fall when conditions can be hot and dry versus the winter and spring with cooler and wetter weather. To meet these fluctuating demands, the treatment unit 1 is preferably provided with a plurality of spray nozzles 11 (e.g., three as illustrated in
In this manner, the operation of the unit 1 and its various components (e.g., control valve 55 upstream of the spray nozzle 11 in
In this regard as discussed above, the collected water 23 is maintained at a desired depth (e.g., 6 feet) in an effort to allow as much remaining air as possible in the collected water 23 to be released and travel upwardly to the water surface 23′. Upon reaching the surface 23′, the released air is then discharged through the discharge duct or vent 29 of the air outlet arrangement. Air in this regard is very undesirable in the collected water 23 to be discharged back into the municipal pipe line 2′ as it can cause undesirable problems (e.g., cavitation, air plugs, and water hammer) in the pump(s) 53 and pipeline 2′. The collected water 23 (e.g., 6 feet high by 8 feet wide by 10 long or about 3500 gallons) is then primarily maintained at the substantially constant depth (e.g., 6 feet) to allow more time (e.g., 5 minutes) for any undesirable air in the collected water 23 to be released. However, it also provides even more opportunity for any remaining liquid THM in the collected water 23 to be contacted by the rising air and volatized and discharged with the rising air through the discharge duct or vent 29.
In a related design feature of the unit 1, the discharge end 21′ of the inclined ramp 21 of
These features are all part of the overall design of the treatment unit or apparatus 1 of the present invention to put as much air as possible into the sprayed water for maximum volatization of the liquid THM and then to take out as much air as possible from the water before returning the water to the municipal pipeline 2′ to avoid problems like cavitation. The air induced by each spray nozzle 11 is on the order of 100:1 (15,000 gallons of air by volume/minute for a spray nozzle with a discharge flow rate of 150 gallons/minute). The air volume being handled is then quite large for the relatively small size of the housing 3 (e.g., 8×8×10 feet) of the unit 1 and in particular the air gap region 51 (e.g., 2×8×10 feet or about 1200 gallons by volume of air space).
The serpentine or C-shaped water path of 19 as in
Similarly, the location of the entrance of the air outlet portion of the discharge duct or vent 29 in
As mentioned above, the unit or apparatus 1 is specifically designed to be relatively small (e.g., 8×8×16 feet inclusive of the housing 3 and its exterior air and water inlets and outlets and weigh on the order of 12,000 pounds) so it can be portable and deployable (e.g., plumbed) wherever needed or desirable along the municipal water distribution system. Normally, this is spaced from and outside of the main water storage reservoirs or tanks of the city which are typically fixed in place and very large (e.g., 20-35 feet high and 30-100 feet wide holding 150,000 to 2,000,000 or more gallons). In this manner, the THM stripping process of the unit 1 can be strategically placed almost anywhere in the municipal water distribution system as needed. This would include downstream of a boost or recharging station of chorine creating an increase in liquid state THM in the water or just anywhere along the distribution system that undesirably high THM readings are detected or occur for whatever reason. Also, as the city expands its distribution system to cover new areas or handle more volume that does not justify the time and cost of building a large, fixed-in-place tank or reservoir or where space to do so is not available, one or more units 1 of the present invention can be deployed to handle any THM problems that may need to be met. Further, because of the relatively small size of the unit 1, the unit 1 can be installed fairly quickly virtually anywhere it is convenient. The serpentine water and air flow paths through the housing 3 as discussed above contribute to the relatively small but effective size of the treatment unit 1.
The relatively small size of the unit 1 also enables it to be placed in an existing structure which can be very advantageous in colder climates particularly if the structure is heated. Such heating among other things can avoid potential problems from frozen pipes and freezing water in addition to favorably providing heated air to the housing 3 to enhance the volatization process within the housing 3 of the liquid THM. To the extent the treatment unit 1 is placed in an existing structure or is otherwise not in an outside, standalone configuration, the air inlet arrangement preferably draws in fresh ambient air entering or in the existing structure. The air outlet arrangement then preferably discharges the mixed air and THM in gaseous state 31 out of the housing 3 through the air outlet duct portion 29 to ambient air at a location outside of the existing structure and away from the air inlet arrangement so as not to contaminate the incoming ambient air. Similarly and even in a standalone configuration, the locations of the drawn-in ambient air 8 and discharged mixed air and THM in gaseous state 31 are preferably spaced well from each other to avoid contamination. In any operating environment, there is then preferably a continuous air flow from ambient or atmospheric air surrounding the housing 3 (i.e., outside of the housing 3 or any structure it is in) through the housing 3 and back out to ambient air.
Whether the unit 1 is in an existing structure or not, periodic maintenance and inspection of the unit 1 is extremely easy and safe to perform as it is normally at ground level and all of the working components (e.g., spray nozzles, pumps, and controls) are outside of the housing 3. Repair people then need not climb up the unit 1 as they would if it were a 20-35 foot or higher tank nor do they need to enter the treatment area within the housing 3 as is usually required with large, fixed-in-place municipal tanks in which many or most of the working components needing inspection and repair are actually inside the tank. For such entry, many states and cities require special, elaborate, and costly training and that strict regulatory and other safety procedures be followed. Special equipment must also often be used such as winches to lower the workers, tethered tools, safety lines, air monitors, inflatable rafts, and even diving gear as well as rescue personnel standing by. Avoiding such entry as in the design of the present treatment unit 1 is very advantageous. Further, the unit 1 of the preferred embodiment preferably induces the air flow through the housing 3 as discussed above without the need and expense of a powered blower (although one could be used if desired).
The above disclosure sets forth a number of embodiments of the present invention described in detail with respect to the accompanying drawings. Those skilled in this art will appreciate that various changes, modifications, other structural arrangements, and other embodiments could be practiced under the teachings of the present invention without departing from the scope of this invention as set forth in the following claims. In particular, it is noted that the undesirable byproducts to be treated by the present invention have been primarily described as being trihalomethanes (THM) resulting from disinfecting processes that use chlorine and chloramines. Such THM exist in liquid state in the processed water and have a relatively high vapor pressure while having a relatively low aqueous solubility. Consequently, THM in liquid state in water easily and quickly volatizes to a gaseous state when exposed to air. However, the apparatus of the present invention is meant to equally encompass treating similar byproducts from other disinfecting processes in which the processed water has undesirable byproducts with similar properties to THM including a relatively high vapor pressure so it easily and quickly volatizes into air. It is also noted that the word substantially is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement or other representation. This term is also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter involved.