Efficiency of Natural Clay Mineral Adsorbent Filtration Systems in Wastewater Treatment for Potential Irrigation Purposes

Abstract

This project investigated the relative efficiencies of three pilot-scale constructed columns for enhancing drainage wastewater treatment processes to ensure compliance with Egyptian and international water quality criteria. In this investigation, basic materials (sand and gravel) and variable natural clay minerals zeolite (Z), diatomite (D) and bentonite (B) were utilized as packing materials to build up a Z column (ZC), D column (DC) and B column (BC), respectively. The three columns’ ability to remove pollutants from waste water for re-use in irrigation was investigated throughout one year (12 trials). The results revealed that the influent water had 211 mg/L total suspended solids, 6.09 mg/L total nitrogen, 36.67 mg/L biochemical oxygen demand, 56 mg/L chemical oxygen demand, 1700 mg/L total dissolved solids, 0.97 mg/L copper (Cu2+), 1.12 mg/L iron (Fe2+), 1.07 mg/L manganese (Mn2+), 1.02 mg/L lead (Pb2+), 1.05 mg/L zinc (Zn2+), and 46 × 103 CFU/mL fecal coliforms. These parameters were higher than the values permitted by Egyptian and international licenses. The range of removal efficiency of these pollutants by ZC was 96–21%, by BC was 99–29.8%, and by DC was 99–19.80%. Regeneration studies for the spent adsorbents demonstrated that the percentages of pollutant removal were sufficiently high. The treated effluent produced by the three columns was suitable for irrigation purposes, especially at a contact time of four hours, with the order for column treatment efficiency being BC ˃ DC ˃ ZC. Treated water was classified for irrigation suitability according to the Agrifood Water Quality Index (AFWQI) as marginal from the ZC, very good from the DC, and excellent from the BC. Treatment of such drainage water using the BC and DC appears feasible, because the process is easily operated and leads to final treated effluent of high quality for agricultural uses. The economic cost also confirms the feasibility of this treatment.

Comparative study for removal of phosphorus from aqueous solution by natural and activated bentonite

“…1 . The XRD pattern of natural bentonite revealed that the major mineral was montmorillonite, with quartz, kaolinite, and dolomite 8 , (Table 1 ). The patterns of Na-bentonite revealed that the major mineral is Na-montmorillonite; with minor amounts of kaolinite, and dolomite also present 31 .…”

“…Regeneration of the spent adsorbents (natural and Na-bentonite) was done by two chemical substances for comparison. The first substance was 1 M KCl 8 ; the two adsorbents were washed gently to remove ions from their surface, then with deionized water to remove any residual, then dried at 80 °C, and left to cool in a desiccator. For the second substance; the same previous method was applied to the spent materials, but with a neutral solution from 5 μM Ethylenedinitrilotetraacetic acid disodium salt dihydrate (Na2-EDTA).…”

“…Most of the crystals are aluminosilicates with cation exchange properties that form natural ion exchange materials. However, some aluminosilicates, like zeolites 7 , 8 , bentonite 8 , 9 , and diatomite 8 , 10 , can operate as anion exchangers. Synthetic and natural adsorbents, or a combination of both, are used as efficient solid materials for adsorption.…”

“…In the last years, researchers have investigated a variety of solid adsorbents to validate if they can be used to reduce phosphorous levels in waterways. Natural Clay minerals such as bentonite, kaolinite, and zeolite and their modified forms, carbonates, and fly ash, have initiated a renewed interest in the removal of many pollutants such as phosphors, cations, and anions by ion exchange, adsorption, or both from aqueous solutions and wastewater due to their low cost and eco-friendly 8 , 13 – 19 .…”

“…Bentonites possess a special position among clay raw materials because of the unique properties of smectites, which consist mainly of calcium and/or sodium montmorillonite 8 , 20 . These days soda activation of bentonite rich in Ca-smectite is a standard industrial practice in manufacturing drilling muds, adsorbents, barrier clays, binders, etc.…”