AU2004100496A4

AU2004100496A4 - UV Disinfection System

Info

Publication number: AU2004100496A4
Application number: AU2004100496A
Authority: AU
Inventors: Owen Hill; Leong Mar
Original assignee: ENVIRO 1 Pty Ltd
Current assignee: ENVIRO 1 Pty Ltd
Priority date: 2004-06-25
Filing date: 2004-06-25
Publication date: 2004-09-02
Anticipated expiration: 2012-06-25

Description

UV Disinfection System Background of Invention Waste water from dwellings can be treated on-site using waste water treatment systems such as composting systems, septic tanks and aerated waste water treatment systems (AWTS). These types of on-site treatment are useful to treat waste water from dwellings in areas not serviced by centralised municipal sewerage services (ie. not connected by sewerage lines). The treated effluent is then usually discharged into the environment.

The land area required for discharge into the environment is dependant on the system capacity and level of treatment offered by the system. As population density increases, property size decreases and dwellings get closer together, the need for better and greater treatment of the waste water increases. It is often more practical, economical and environmentally astute especially in areas where water resources are scarce or limited to be able to reuse the treated water. However, the water reuse applications are determined by the level of treatment and resultant quality of the treated water. The guidelines/specifications for the minimum quality of treated water that can be discharged or reused for particular purposes are usually set by health and regulatory authorities.

In more recent times AWTS have become the popular choice. AWTS normally consist of 3 treatment steps: 1. Primary treatment physical separation, settling, anaerobic treatment 2. Secondary treatment aerobic treatment, further separation 3. Tertiary treatment disinfection The 3 treatment steps are usually performed in connected but physically separate chambers or compartments, see Figure 1.

There are a variety of Tertiary treatment options to effect disinfection. Most are influenced by the desire for low environmental impact, low cost and low maintenance. Furthermore, any Tertiary treatment process that increases the number of potential uses for the treated water is an added benefit.

"UV Disinfection System" Page 1 Chlorination is most commonly used method for disinfection because of the low cost, ease of use, residual disinfection and ability to cope with high capacity.

However there are drawbacks with the chlorination method, such as the potential for variable germicidal action and variable treatment, tendency for over treatment, leaving organochlorine residues in environment and unpleasant odour. Another factor to consider with Chlorination is that it is not immediate disinfection, there is a retention time needed to ensure contact with chlorine and for the chemicals to take effect. This limits the number of potential purposes for which the treated water can be used for.

Many large municipal treatment works use other methods such as ozone disinfection and UV disinfection. UV disinfection is a preferred method because the germicidal action has the potential to kill all pathogens, high capacity, no over treatment, no unpleasant odour, and immediate disinfection. However, present

UV

disinfection methods have drawbacks. For example there is usually no residual disinfection. Also, the cost can be high, up to hundreds to thousands of dollars, which may be acceptable for centralised municipal systems but likely to be prohibitive for typical on-site installations.

It is known to implement a UV disinfection system based on a UV source (lamp), the UV source needs to be enclosed in UV transmitting material like quartz or fluoropolymer. The enclosed UV source is immersed in the water flow, usually contained within pipes made from materials impervious and resistant to UV radiation such as stainless steel. In this type of system the UV source is always in contact with the water it is treating and the water flow is pressurised to ensure total coverage of the UV lamp, see for example Figure 2.

The implementation of systems such as those in Figure 2 can operate effectively when the quality of the incoming water is high, for example to treat water for human consumption as drinking water. However problems arise with this type of system attempting to treat waste water where the quality of the incoming water can be very variable.

"UV Disinfection System" Page 2 The variable quality of the incoming water greatly increases the potential for fouling of the UV source enclosure. Such fouling reduces the effective UV radiation intensity and therefore leads to an unsatisfactory level of disinfection and increases the potential for under-treatment. The result is that regular services are required to clean the UV enclosure. This increases cost and complexity for use, especially in on-site systems.

The present invention seeks to provide improved methods of UV treatment.

Description of the Invention The present invention relates to a non contact, low cost, low maintenance

UV

disinfection system. In the preferred embodiment the invention is suitable for on-site water disinfection. The invention addresses issues such as fouling and residual disinfection.

In the present invention the water being treated does not come into contact with the UV source. The water flows through a vessel such as a trough, pipe or tube and the height/depth of the water in the vessel can be determined by a weir or the position of the outlet. The maximum water height is adjusted so that there is always a gap between the UV source and the water. The gap may be an air region. Other suitable UV transmissive material may also be used to separate the UV source from the water. The presence of the gap region means that the water does not come into contact with the UV source thereby reducing or eliminating fouling due to the variability of the water being treated.

Figure 3 shows preferred embodiments of the present invention In the present invention the UV disinfection unit is open to atmospheric pressure and the water entering the unit is not pressurised. The water flowing through the unit does so under gravity. This helps reduce the cost because the components do not have to withstand pressure.

To enhance treatment it is possible to place reflective surfaces in locations around the UV source so as to reflect radiation onto water and increase effectiveness. It is "UV Disinfection System" Page 3 also possible to use the weirs or obstacles placed within the flow path to control flow height to also create turbulence in the water and improve mixing and UV disinfection.

The system has the advantage that it could be fitted into tertiary treatment chamber of new AWTS or retrofitted into existing systems. The UV lamp is enclosed in UV transmitting material for protection and safety issues. The invention is applicable to other water processing or storage facilities such as rain water or storm water tanks.

In another embodiment the issue of residual disinfection is addressed by recirculating the treated (or partially treated) water through the UV disinfection unit, see for example Figure 4. For example when the UV disinfection system is placed within a water storage chamber, the UV disinfection system may be configured to be always on thus improving or maintaining the quality of the water in the chamber. In this embodiment when no incoming flow is detected, water that is already treated is recirculated through the UV disinfection system for ongoing treatment. Alternatively, water is constantly recirculated using an arrangement where the incoming flow includes a portion of already treated water so that even in the event of no new incoming water to be treated, the water flowing through the unit is already treated water.

It will be appreciated by the person skilled in the art that numerous modifications and/or variations may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

In the claims that follow and in other descriptions of the invention, except where the context requires otherwise due to express language or necessary implication the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.

"UV Disinfection System" Page 4

Claims

1. A waste fluid treatment system comprising: a fluid inlet a fluid flow path a UV source a fluid outlet wherein the UV source disinfects fluid in the fluid flow path and a non-contact region is maintained between the fluid flow path and the UV source.

2. A waste water treatment system as claimed in claim 1 further comprising reflective surfaces protrusions in the fluid flow path wherein the reflective surfaces reflect the radiation from the UV source towards the fluid flow path and the protrusions determine the flow characteristics of the fluid flow

3. A waste water treatment system comprising a fluid inlet a fluid flow path a UV source a fluid outlet a treatment chamber wherein the UV source disinfects fluid in the fluid flow path, a non-contact region is maintained between the fluid flow path and the UV source and the system is arranged, in use, to allow recirculation of the fluid for repetitive treatment. END of CLAIMS "UV Disinfection System" Page