The studied remediation alternatives were irrigating with freshwater (FW), diluting TWW with an equal proportion of FW (MIX), high volume and long irrigation intervals (LFI), and installation of tuff trenches (TUF). Obviously, the low levels of salts and other harmful materials in freshwater makes it ideal for irrigation. Irrigation with freshwater might improve physicochemical characteristics of soil already adversely affected by long term irrigation with TWW compared with poor quality water (e.g., TWW).
However, there is a scarcity of FW in Arid and semi-arid areas, thus its use as a sole irrigation water source may not be feasible and/or economical. So that another feasible alternative that would either reverse or prevents further damages to soil are required. The second alternative remediation studied, MIX might be a reliable alternative for sustainable agriculture.
This amendment might reduce the salinity, and ions concentration in irrigation water thereby reducing the SAR content of the irrigation water, which may reduce the negative effects of TWW on the soil. Reducing the SAR of the TWW before its allocation to irrigation is crucial for sustainability and prevent soil degradation (Assouline et al., 2016).
Pedrero and Alarcón (2009) reported improved agronomic quality of reclaimed wastewater by mixing it with well water of equal amount. The third remediation evaluated, LFI might enhance leaching of salinity that would improve the aeration of the soil negatively affected with long term irrigation with treated wastewater.
Higher rate of irrigation with the effluent of medium salinity might leach salts to the lower horizons and might reduce salinity buildup (Stewart et al., 1990). Tuff trenches installation is the fourth remediation alternative evaluated. Tuff has become a popular growth media in Israel due to its high porosity (Papadopoulos et al., 2008; Silber and Raviv, 1996), high saturated hydraulic conductivity (Silber and Raviv, 1996) and high surface area (Papadopoulos et al., 2008).
The high porosity and high-saturated hydraulic conductivity of tuff are excellent for leaching of solutes from the soil profile and reversing the limited hydraulic conductivity of the soil irrigated with TWW for long-term. In a numerical analysis of solute transport, Russo et al. (2008) found a fast vertical flow of water and solute in tuff pond strips as compared with local soil and sand.
It also creates better air circulation and water movement in the soil that may induce better root growth. Moreover, the rapid downward movement of water in the top 30 cm of soil covered with tuff might allow the water solution to reach the soil profile where it cannot be easily lost due to evaporation.