Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Biological and Irrigation Engineering

Department name when degree awarded

Irrigation Engineering


Gary P. Merkley


A general systematic framework with several sub-frameworks was developed to help managers make informed decisions related to the reuse of treated wastewater in agricultural irrigation. The framework involves the identification and evaluation of the short- and long-term effects of using treated wastewater with some common constituents of concern ( e.g. salts and some specific ions, nutrients, heavy metals, organic compounds, and microorganisms) on the environmental elements ( crop , soils, surface water, and groundwater), and on the public health. Local and/ or international standards, criteria, and guidelines related to agricultural reuse are applied to the evaluation of the effects. Based on the evaluation results, decisions are made and management alternatives are proposed. The management alternatives include improving the wastewater treatment level , blending treated wastewater with good-quality water, using an appropriate irrigation method, using different reuse schemes, and zero discharging from specific industries.

The framework demonstration includes the data input, information processing, output, evaluation, and decision-making phases. Data related to the plant-soil system (crop, soil, and any other assimilation pathway), and the behavior and fate of treated wastewater constituents are necessary for the identification of the effect on the environmental elements. Jordan was selected as a case study for the demonstration of the general systematic framework. Due to the lack of data related to the different constituents, some of the hazardous heavy metals were considered in the demonstration with the worst condition of accumulating the whole quantity of metals in the soil. The demonstration results showed that, at least for the coming 40 years Jordan can practice the reuse of the treated wastewater for agricultural irrigation without exceeding the maximum allowable limits in the agricultural soils based on the USEPA for biosolid application. With regard to blending and system efficiency, the demo result s also showed that they do not have an effect on the long-term accumulation of the hazardous metals in the soil.

The general systematic framework is a decision tool, which is able to answer questions related to water treatment level and type , when to blend with freshwater, the recommended blending ratio, the recommended irrigation method, selection of the optimum reuse scheme, as well as providing answers to questions related to industrial wastewater constituents.