| Pilot Study of Hybrid Two-Stage Reverse Osmosis with Intermediate Concentrate Demineralization: Secondary RO Criteria, Economic Feasibility |
| کد مقاله : 1400-IWWA |
| نویسندگان |
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Gholamreza Khosravi Mehr1، Maryam Esmaeili *2، Forouzan Amerizadeh3، Fariba Mirzaienia4 1Farnam Faraz Firouzeh Company, Iran 2Farnam Faraz Firouzeh Company, Iran University of Milan (Università degli Studi di Milano, UNIMI), Milan, Italy 3Farnam Faraz Firouzeh Company, Iran Ferdowsi University of Mashhad, Mashhad, Iran 4Isfahan University of Medical Science, Isfahan, Iran |
| چکیده مقاله |
| Inland brackish-water reverse osmosis (BWRO) systems are commonly constrained by mineral scaling, and concentrate disposal is often costly. This study evaluates a hybrid configuration in which the concentrate from a first RO stage (RO1) undergoes intermediate concentrate demineralization (ICD) via chemical softening and re-acidification, and is subsequently treated in a second RO stage (RO2). Two years of operational data from a 20 m3/d pilot plant treating brackish groundwater (TDS 5,010 mg/L) in Isfahan, Iran, were assessed using ion-by-ion mass balances, saturation-index calculations, and a cost model based on pilot-scale prices. RO1 achieved 75% recovery. Softening the RO1 concentrate with NaOH followed by re-acidification with HCl removed 95. removed 95.8% Ca²⁺, 96.9% Mg²⁺, 97.5% Ba²⁺, 93.7% HCO₃⁻ and 87.4% SiO₂, while sulfate and TOC were essentially unchanged. RO2 recovered 60% of the treated concentrate with 98.9% salt rejection. Overall recovery increased to 90.0%, brine volume decreased from 25% to 10% of the feed, and blended product water reached 75 mg/L TDS. Modeling indicates that, without softening, calcite, silica, and gypsum would have exceeded scaling limits in RO2, and acidification alone would have limited RO2 recovery to 32% because of silica. After softening, no major scalant reached saturation in the final brine; the limiting factor became osmotic pressure. The results show that ICD can substantially improve inland BWRO recovery and the economic benefit is primarily determined by softening-chemical demand relative to the value of additional water and avoided brine-disposal costs. |
| کلیدواژه ها |
| Reverse osmosis concentrate, Intermediate concentrate demineralization, Secondary RO, High-recovery desalination, Mineral scaling, Brine minimization |
| وضعیت: پذیرفته شده برای ارائه شفاهی |
