| Sampling and monitoring of irrigation water Before supplying recycled water for irrigation purpose, there should be performed an analysis of the quality of this water, interpreting results, search for solutions (i.e. good management practice, use of water treatment solutions and technology as provided by Lenntech) and monitoring frequently.
For example, water with low quality and big concentration of salt may require a reverse osmosis treatment system. Water with only minor quality problems may only require slight changes in supplemental fertility.
The procedure to take samples will affect the precision and reliability of the water quality data and determine its interpretation. it is important to monitor quality standards on a frequent basis to avoid potential problems. |
Some general considerations to take into account when making lab test of irrigation water are listed below:
- Usually 1L of sample is sufficient - All samples should be labelled to indicate date, location, time and other pertinent data. - Take seasonal samples for representative data due to variation of water quality by climate conditions - Take samples before and after the treatment plant for recycled water and other representative samples when appropriate such as after the storage tank, etc. Recommendations for samples preparation & conservationThe following table compile the recommendations for samples preparation & conservation | Parameter | Type of bottle1 | Addition of chemicals | Conservation | Comments | | Anions and cations (Chloride, sulphate, etc.), all forms of nitrogen and phosphorus, as well as general physicochemical parameters (PH, SS, conductivity, etc.) | 1 L plastic, with or without air | No additive | Dark, 4°C | Temperature and dissolved oxygen should be measure on site | | COD | 100 mL, plastic, no air | Sulphuric acid | Dark, 4°C | No additive is needed if the samples are analyzed within 48h | | BOD | 500 mL, plastic, no air | No additive | Dark, 4°C | | | Trace elements | 250mL, plastic, with or without air | Nitric acid | Dark, 4°C | A special bottle and additive is needed for the analysis of mercury (Hg) | | Trace organics and pesticides | 1L, dark glass bottle, no air | No additive | Dark, 4°C | | | Microbiological parameters (total and faecal coliforms, heminths, viruses, etc.) | 1-5L, sterile plastic bottle, with air | No additive | Dark, 4°C | Additive should be added only to disinfected effluent (sodium thiosulfate in presence of residual chlorine) |
Source of information: Valentina Lazarova Akiçca Bahri; Water Reuse for irrigation: agriculture, landscapes, and turf grass; CRC Press.
1. Plastic bottles are preferred because glass bottles may introduce boron to the samples.The following table compile the recommendations for samples preparation & conservation: | Monitored parameters | Raw wastewater & recycled water | Receiving soils | Groundwater Shallow aquifers Deep aquifers | Coliforms | Weekly to monthly | - | Bi-annual | Annual | | Turbidity | On-line for unrestricted irrigation | - | - | - | | Chlorine residual | On-line for unrestricted irrigation | - | - | - | Volume | Monthly | - | - | - | Water level | - | - | Bi-annual | - | | PH | Monthly | Annual | Bi-annual | Annual | | Suspended Solids | Monthly | - | - | - | | Total dissolved solids | Monthly | - | Bi-annual | Annual | Conductivity (ECi) | Monthly | Bi-annual (ECe) | Bi-annual | Annual | BOD | Monthly | - | - | - | Ammonia | Monthly | - | Bi-annual | Annual | Nitrites | Monthly | - | Bi-annual | Annual | Nitrates | Monthly | Annual (exchangeable NO3) | Bi-annual | Annual | Total Nitrogen | Monthly | Bi-annual | Bi-annual | Annual | | Total phosphorus | Monthly | Bi-annual (extractable P) | Bi-annual | Annual | | Phosphates (soluble) | Monthly | Bi-annual | Bi-annual | Annual | | Major solutes (Na, Ca, Mg, K, Cl, SO4, HCO3, CO3) | Quarterly | Bi-annual | Bi-annual | Bi-annual | | Exchangeable cations (Na, Ca, Mg, K, Al) | | Annual | - | - | | Trace elements | | - | - | - |
Source of information: Valentina Lazarova Akiçca Bahri; Water Reuse for irrigation: agriculture, landscapes, and turf grass; CRC Press. |