The overuse of pig slurry for fertilization purposes could involve an environmental risk. Pig slurry has been scarcely treated using constructed wetlands and stabilization ponds. Further information on hydraulic retention time comparison at full-scale in farms is desired. This survey aims to optimize a low-cost system comparing two hydraulic retention times (3 and 7 days) to purify pig slurry. Physical, chemical and microbial parameters were tested. A mechanical separator provided homogenous influent to feed the constructed wetland. Seven days of retention presented higher COD and N removal while 3 days of retention was more effective to remove TP and SO₄ ²⁻ in the constructed wetland. However, higher removal efficiencies were registered performing 7 days of retention for Mn (148.1 %), TP (113.4 %), KN (102.6 %), COD (102.5 %), NH₄ ⁺-N (94.0 %), TC (87.9 %), Cu (64.2 %), FS (47.4 %), NO₃ ⁻ (36.6 %), Ca²⁺ (32.1 %), and Br⁻ (26.0 %) in the whole system, pointing out the positive effect of the storage pond. Though the main potential pollutants were effectively reduced, parameters such as Fe, SO₄ ²⁻, SS, Zn and NO₂ ⁻ increased after purification.

This study compared the behaviors of two classic advanced oxidation processes (AOPs), hydroxyl radical-based AOPs (•OH-based AOPs) and sulfate radical-based AOPs (SO₄ •⁻-based AOPs), represented by UV/ hydrogen peroxide (H₂O₂) and UV/peroxydisulfate (PDS) systems, respectively, to degrade humic acid (HA) in the presence of halide ions (Cl⁻ and Br⁻). The effects of different operational parameters, such as oxidant dosages, halide ions concentration, and pH on HA degradation were investigated in UV/H₂O₂/Cl⁻, UV/PDS/Cl⁻, UV/H₂O₂/Br⁻, and UV/PDS/Br⁻ processes. It was found that the oxidation capacity of H₂O₂ and PDS to HA degradation in the presence of halides was nearly in the same order. High dosage of peroxides would lead to an increase in HA removal while excess dosage would slightly inhibit the efficiency. Both Cl⁻ and Br⁻ would have depressing impact on the two AOPs, but the inhibiting effect of Br⁻ was more obvious than that of Cl⁻, even the concentration of Cl⁻ was far above that of Br⁻. The increasing pH would have an adverse effect on HA decomposition in UV/H₂O₂ system, whereas there was no significant impact of pH in UV/PDS process. Furthermore, infrared spectrometer was used to provide the information of degraded HA in UV/H₂O₂/Cl⁻, UV/PDS/Cl⁻, UV/H₂O₂/Br⁻, and UV/PDS/Br⁻ processes, and halogenated byproducts were identified in using GC-MS analysis in the four processes. The present research might have significant technical implications on water treatment using advanced oxidation technologies.

Measurements of major ions, trace elements, water-stable isotopes, and geophysical soundings were made to examine the interaction between Urmia Aquifer (UA) and Urmia Lake (UL), northwest Iran. The poor correlation between sampling depth and Cl⁻ concentrations indicated that the position of freshwater-saltwater interface is not uniformly distributed in the study area, and this was attributed to aquifer heterogeneities. The targeted coastal wells showed B/Cl and Br/Cl molar ratios in the range of 0.0022–2.43 and 0.00032–0.28, respectively. The base-exchange index (BEI) and saturation index (SI) calculations showed that the salinization process followed by cation-exchange reactions mainly controls changes in the chemical composition of groundwater. All groundwater samples are depleted with respect to δ¹⁸O (−11.71 to −9.4 ‰) and δD (−66.26 to −48.41 ‰). The δ¹⁸O and δD isotope ratios for surface and groundwater had a similar range and showed high deuterium excess (d-excess) (21.11 to 31.16 ‰). The high d-excess in water samples is because of incoming vapors from the UL mixed with an evaporated moisture flux from the Urmia mainland and incoming vapors from the west (i.e., Mediterranean Sea). Some saline samples with low B/Cl and Br/Cl ratios had depleted δ¹⁸O and δD. In this case, due to freshwater flushing, the drilled wells in the coastal playas and salty sediments could have more depleted isotopes, more Cl⁻, and consequently smaller B/Cl and Br/Cl ratios. Moreover, the results of hydrochemical facies evolution (HFE) diagram showed that because of the existence fine-grained sediments saturated with high density saltwater in the coastal areas that act as a natural barrier, increasing the groundwater exploitation leads to movement of freshwaters from recharge zones in the western mountains not saltwater from UL. The highly permeable sediments at the junction of the rivers to the lake are characterized by low hydraulic gradient and high hydraulic conductivity. These properties enhance the salinization of groundwater observed in the study area. The main factors influencing the salinity are base-exchange reactions, invasion of highly diluted saltwater, dissolution of salty pans, and water chemistry evolution along flow paths.