treatment of sewage for irigation purposes

[mechanicaldup]

hello,
what water treatment processes are required on sewage to re-use the it for irigation purposes?

 

[bimr]

Very general question. There is no standard treatment method. You need to contact the regulatory agency where you are located. A general guideline for water reuse can be found in the Title 22 California regulations.

Treatment would generally consist of secondary treatment, tertiary filtration, and disinfection.

60304. Use of recycled water for irrigation
(a) Recycled water used for the surface irrigation of the following shall be a disinfected
tertiary recycled water, except that for filtration pursuant to Section 60301.320(a)
coagulation need not be used as part of the treatment process provided that the filter
effluent turbidity does not exceed 2 NTU, the turbidity of the influent to the filters is
continuously measured, the influent turbidity does not exceed 5 NTU for more than 15
minutes and never exceeds 10 NTU, and that there is the capability to automatically
activate chemical addition or divert the wastewater should the filter influent turbidity
exceed 5 NTU for more than 15 minutes:
(1) Food crops, including all edible root crops, where the recycled water comes
into contact with the edible portion of the crop,
(2) Parks and playgrounds,
(3) School yards,
(4) Residential landscaping,
(5) Unrestricted access golf courses, and
(6) Any other irrigation use not specified in this section and not prohibited by
other sections of the California Code of Regulations.
(b) Recycled water used for the surface irrigation of food crops where the edible portion
is produced above ground and not contacted by the recycled water shall be at least
disinfected secondary-2.2 recycled water.

http://www.dhs.ca.gov/ps/ddwem/publications/waterrecycling/index.htm

 

[mechanicaldup]

What type of disinfection is recomended; chlorination or UV Sterilisation ?

 

[bimr]

UV with a chlorine residual.

 

[stanier]

UV is generally accepted as the most economic depending upon the scale of the facility.

Be careful with chlorination as this can cause a build up of chlorides . At Rouse Hill NSW Australia which is a large recycle water facility they chlorinate and dechlorinate then use UV before the water is reticulated to houses for flushing toilets, watering etc.

Cronula STP also in NSW uses tertiary treatment then UV and the water is used on golf courses. No post chlorination.

 

[bimr]

You can use UV or chlorine as the primary disinfectant, but it is esential to have a chlorine residual in the finished water. Without the chlorine residual, you will get fouling and corrosion in your piping system.

Most applications are now using UV with a chlorine residual.

The amount of chlorine used in water and wastewater treatment plants is so small that it is impossible to ever get a significant concentration of chlorides as suggested in the previous poster's comment regarding "build up of chlorides".