Microirrigation of wastewater effluent
Ted Sammis
Introduction.
Wastewater is normally applied as land application using flood or sprinkler irrigation systems because of the plugging problems associated with using a drip irrigation system. However, researchers have applied wastewater through drip irrigation systems where the drip system was a self-flushing and tortuous -path turbulent flow emitter system and also using drip tape where the drip tape was manufactured by molding or attachment of the emitter. The research indicated that drip laterals should be flushed with a minimum velocity of 0.5 m/s every two week and that a sand media filer be used along with chlorination of 150 mg/l NaOCl for three hours every 10 days or more frequent is bacterial slime growth is detected in the sand media filter. Flushing of the sand media filter should be height enough to prevent slime build up in the filters. However, the research was done using effluent from an activated sludge wastewater treatment plant where the BOS and TSS are less than in a lagoon wastewater treatment system. Table 1. Wastewater from Ismailia has been applied using drip irrigation with tortuous-path emitters and no major clogging has occurred. The wasterwater sites (table 2) in Wisconsin have not shown any plugging problems and the TSS and BOD were higher than the effluent from the wastewater treatment plant at Davis California and the lagoon system in Egypt.
The best management practice for the application of effluent from a lagoon wastewater system should be the use of a drip system than has tortuous -path emitters or drip tape with molding or attachment emitters. Also the system should have both a sand media and screen filter and chlorine be injected into the system along with a regular flushing cycle.
Table 1. Water quality effluent from different Wastewater treatment systems.
|
Parameter/Site |
Ojinaga, Mexico
|
Las
Cruces, USA |
Ismailia,
Egypt |
Davis California |
|
Treatment Train |
Screens/Primary/Anaerobic lagoon |
Screens/Primary/Aerated Lagoon |
Screens/Grit/Primary/Aerated /Facultative Lagoon |
Activated sludge wastewater treatment plant |
|
Disinfection |
No |
No |
No |
Yes |
|
Effluent
BOD, mg/L |
29-43 |
30 |
46 |
15.2 |
|
Effluent TSS, mg/L |
15 |
30 |
23 |
8.3 |
|
Effluent TN, mg/L |
14-37 |
45 |
45 |
|
|
Effluent TDS, mg/L |
1,950-2,220 |
2,000-3,000 |
550 |
|
|
Soil SAR, mg/L |
5.5 – 7.0 |
N/A |
N/A |
|
|
Flow, m3/day |
6,048 |
1,514 |
90,000 |
|
|
Land
Application. Area, ha |
500 |
22.3 |
200-2000 |
|
|
Rainfall, mm/year |
280 |
216 |
<2.0 |
|
|
PET, mm/year |
2,450 |
2,220 |
2,341 |
|
|
Selected Crop(s) |
Eucalyptus/Hybrid Popular |
Creosote
Bush, FourWing Saltbush, Mesquite |
Arizona
Cypress, Afghan Pine, Eucalyptus, and others |
|
| Irrigation system | flood | sprinkler | Drip turbulent flow emitters | Drip tape. |
Table 2. Effluent of septic for different locations in Wisconsin
|
Parameter/Site |
Barron Rest Area | Fond Du Lac Home | Wood -School |
|
Treatment Train |
Septic Tank | Septic Tank | Septic Tank |
|
Disinfection |
no | no | no |
|
Effluent
BOD, mg/L |
173 | 110 | 24 |
|
Effluent TSS, mg/L |
51 | 20 | 49 |
|
Effluent TN, mg/L |
185 | 45 | 92 |
|
Effluent TDS, mg/L |
2906 | 6718 | 1921 |
|
|
pressure compensating emitters 0.65gph | pressure compensating emitters 0.65gph |
None of the system have been running for more than 3 years. Plugging may still be a problem because no chlorination is occurring
Reference Hills, D. J. and M. J. Brenes, 2001. Microirrigation of wastewater effluent using drip tape Applied Engineering in Agr. vol. 17(3):303-308
Bohrer R. M. and J. C. Converse. 2001. Soil treatment performance and cold weather operations of drip distribution systems On Site wastewater treatment prodceedings of the ninth national symposium on infividual and samm community sewage system March 1-14 For Worth, Texas pp561-584