|M.Sc Student||Nanak Khadya|
|Subject||The influence of treated and raw olive mill wastewater|
on soil chemo-physical properties as measured
by electromagnetic induction
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Emeritus Shaviv Abraham|
|Full Professor Michael Iggy Litaor|
|Full Thesis text - in Hebrew|
Among the many research works, which examined the influence of Olive Mill Wastewater (OMW) spreading, the majority report positive effects on soil properties. However, most of those works did not examine the influence of OMW spreading on soil structural stability, exchangeable sodium percentage (ESP), hydraulic conductivity, hydrophobicity and their spatial distribution. Fewer works examined the possibility of reusing Treated Olive Mill Wastewater (TOMW) for irrigating agricultural soil.
The research objectives are: 1) examine the influence of TOMW irrigation on soil chemo-physical properties, and 2) evaluate the influence of OMW spreading on soil chemo-physical properties, using the electromagnetic induction method to measure the apparent electrical conductivity (ECa) and relate ECa to soil properties.
Research consisted of: A. Lysimeters experiment with 3 treatments: TOMW irrigation, fresh water irrigation (Dan) and artificially saline Dan water with similar salinity to TOMW irrigation. Soil was sampled 5 times during 4 months of irrigating young olive trees to examine the change in soil properties. B. OMW spreading effect evaluated at an olive orchard with known history of OMW spreading. The olive orchard was surveyed using an EM38-MK2 system to measure soil ECa. Grouping analysis allowed creation of 4 groups with homogeneous ECa. Eight soil profiles were sampled based on the grouping analysis results.
Lysimeter experiment results showed that TOMW irrigation increased the ECe, pH, sodium adsorption ratio (SAR), potassium adsorption ratio (PAR) and dissolved organic carbon (DOC). This increase was mainly observed in the upper soil and is statistically significant compared to Dan irrigation (p<0.05). ESP increased due to TOMW irrigation and hydraulic conductivity decreased due to TOMW. The decrease in hydraulic conductivity exhibited negative correlation (r=-0.6, P < 0.05) to DOC. TOMW irrigation didn't induce hydrophobicity effect. Irrigation with TOMW caused decrease of NO2-3-, possibly due to pH rise in soil which inhibits nitrification.
ECa grouping is best explained by 5 soil properties, as determined by Discriminant analysis procedure (DA). Discriminant functions based on sand, effective cation exchange capacity (ECEC), pH, ESP and SAR successfully reclassified ECa groups. Orchard soil analysis showed high values of ECe, ESP and SAR, but those high values were limited to surface soil samples. This result indicates the influence of irrigation water quality and not OMW spreading. Comparing SAR, PAR, ECe and pH to control soil showed no significance difference suggesting the lack of OMW influence on soil properties. ECa values were found in moderate correlation with ECEC and soil water content. The Dual Pathway Parallel Conductance, also showed that water content is the main soil attribute affecting ECa
Research conclusions are : 1) Reuse of TOMW irrigation is not recommended due to the significant increase in ECe, pH, SAR, PAR, DOC and the decrease in Hydraulic conductivity. 2) Controlled OMW spreading at levels of 50 m3ha-1 is an environmental safe application, 3) Measuring ECa is a promising tool to decide sampling locations, 4) Correlations of ECa with water content and ECEC support the notion that spreading OMW has negligible impact on the soils of this study.