Primary RO Research Articles

Permeate quality, advanced oxidation process treatability, and cost for two concentrate treatment technologies to enhance recovery for potable reuse

Abstract Closed circuit reverse osmosis (CCRO) and forward osmosis-RO (FO-RO) were evaluated at a pilot scale to generate additional permeate from RO concentrate – achieving a recovery of 61% for CCRO and 35% for FO-RO – at a full-scale advanced water purification facility. This study assessed permeate water quality, suitability of the permeate for treatment by an ultraviolet-advanced oxidation process (UV-AOP), and cost/footprint for a conceptual 10- or 20-mgd system. Both technologies demonstrated inorganic, organic, and microbiological constituent removal suitable for blending with primary RO permeate. Virus challenge testing with MS coliphage demonstrated ≥3.7-log removal by both technologies. Pilot-scale UV/hydrogen peroxide AOP treatment of CCRO or FO-RO permeate yielded similar performance (∼1.4-log N-nitrosodimethylamine removal and ∼0.5-log 1,4-dioxane removal) as the full-scale UV-AOP that treats the RO permeate from the purification facility. The estimated full-scale total unit cost (capital plus operation and maintenance costs) of product water produced by the two technologies was estimated to range from $0.91 to $1.12 per cubic meter, depending on the design flow rate of RO concentrate treated, and is estimated to be similar between the two technologies given the +50%/–30% expected accuracy of the Class 5 cost estimate.

Desupersaturation of RO concentrate and gypsum removal via seeded precipitation in a fluidized bed crystallizer

The feasibility of a continuous chemically-enhanced seeded precipitation (CCESP) process was evaluated for desupersaturation of primary reverse osmosis (PRO) concentrate generated from RO desalting of inland agricultural drainage (AD) water with high gypsum scaling potential. The CCESP approach, comprised of partial lime treatment (PLT) followed by gypsum seeded precipitation (GSP), was assessed via laboratory and field tests, along with model simulations. PLT effectiveness was confirmed for residual antiscalant removal from the PRO concentrate, which otherwise would suppress gypsum crystallization. GSP was carried out in a fluidized bed crystallizer (FBC) demonstrating the feasibility of continuous PRO concentrate desupersaturation with suitable solids management. FBC operation was stable, with respect to desupersaturation performance, when operating over a sequence of periodic solids purge-only mode with intermittent seeds replenishment. The study suggests that CCESP integration with primary and secondary RO desalting (i.e., PRO-CCESP-SRO) can provide for significant enhancement of product water recovery for inland water of high gypsum scaling propensity. For example, source water of high salinity (14,347 mg/L total dissolved solid) AD water, nearly saturated with respect to gypsum, could be desalted up to a recovery of 88-96% (relative to merely 66% recovery feasible via PRO desalting. Moreover, net salt harvesting of 2.6-3.6 kg per m3 RO concentrate (with concentrate recycle) can be obtained from high recovery desalting of the above PRO concentrate.

Вектор Пойнтинга и новая теория трансформатора. Ч. 6. «Анатомия» автотрансформатора

Thepreviouspartofthearticle(seeElektrich estvo No. 6, 2018 [1]) described a new theory of anautotransformer, according to which the primary ro le is played by two flows of Poynting vector, namely, the electrical and electromagnetic ones, which are subs equently reflected in the equivalent twotransformer circuit.The specific feature of this circuit is that it separately contains the transformer itself without conductive connections between its primary and secondary windings. Owing to this feature, conditions were setup for using statements that have led to the notion about the “transformer anatomy” (see Elektrichestvo, No.3,2017)[2]inconnectionwiththefactthatanA invariant surface was revealed inside each of its windings, such that the vector potential (A) on it d oes not depend on the load on the other winding. Obviously, the magnetic fluxembraced by this surface has the same property, and it should be noted that the latter acquires also the sense of a Фinvariantsurface. The aim of this studyistoes tablish distinctive, ascompared with a transformer, specific features per tinent to distribution of the vector potential in an autotransformer and to disclose their role in understanding the physical processes occurring in the device under any operating conditions, including detailed clarification of factors causing its degraded (according to the data of the AllRussia Electrical Engineering Institute, CIGRE, and IEC)dynamic withstand capability in case of a shortcircuit fault [3—5].

Use of beach galleries as an intake for future seawater desalination facilities in Florida and globally similar areas

Desalination of seawater using the reverse osmosis process can be made less costly by the use of subsurface intake systems. Use of conventional open-ocean intakes requires the addition of a number of pretreatment processes to protect the primary RO process. Despite using the best designs possible for the pretreatment, seawater RO membranes tend to biofoul because of the naturally-occurring organic material and small bacteria present in seawater. These materials are not completely removed by the pretreatment system and they pass through the cartridge filters into the membranes, thereby causing frequent and expensive cleaning of the membranes. Quality of the raw water can be greatly improved by the use of subsurface intakes which can substantially reduce the overall treatment cost. There are a number of possible subsurface designs that can be used including conventional vertical wells, horizontal wells, collector wells, beach galleries, and seabed filters. The key selection criteria for the type of subsurface intake most suited and most cost-effective for a site are based on the required volume of raw water and the local geology. The active shorelines of Florida are very well-suited for the development of beach gallery intake systems. These systems are installed beneath the active beach between the high and low tide zones of the beach. Since they are constructed with a depth to the screens between 3 and 5 m, they cannot be observed at surface and persons using the beach would be unaware of their existence. These galleries are simple to construct and they tend not to clog because the active wave action within the intertidal zone provides mechanical energy that continuously cleans the filter face. They also have other advantages, including: the water quality is seawater unaffected by substances present in freshwater aquifers occurring landward of the shoreline, the salinity of the water is generally constant, and there are no impacts on water users located inland from the shoreline. A comprehensive study of the grain size characteristics of Florida beaches has allowed an assessment to be made of the hydraulic conductivities of the Florida beach sands. Hydraulic conductivity values generally range from 1.8 to 24 m/day, which is more than sufficient to allow the design and construction of high-capacity galleries at a reasonable cost. This type of intake is particularly relevant to the northeast Florida shoreline adjacent to an area being considered for development of a large-capacity seawater desalination system.

Antiscalant removal in accelerated desupersaturation of RO concentrate via chemically-enhanced seeded precipitation (CESP)

An experimental study was carried out to demonstrate and quantify the feasibility of antiscalant (AS) removal from brackish water RO concentrate of high gypsum scaling propensity via lime treatment prior to seeded gypsum precipitation. Based on studies with model solutions, it was shown that sufficient AS removal (up to ∼90%) from RO concentrate is feasible via a lime treatment step (at a dose significantly lower than that required for conventional lime softening) to enable effective subsequent seeded gypsum precipitation. This two-step chemically-enhanced seeded precipitation (CESP) treatment of primary RO concentrate is suitable as an intermediate concentrate demineralization (ICD) stage for high recovery desalting employing secondary RO desalination. Analysis of gypsum precipitation and lime treatment kinetic data suggests that, after adequate CaCO3 precipitation has been induced for effective AS scavenging, CaSO4 desupersaturation can be achieved via seeded gypsum precipitation without retardation due to seed poisoning by AS. Also, the lime dose required to prevent seed poisoning during subsequent gypsum desupersaturation via seeded gypsum precipitation can be adequately assessed with a precipitation kinetics model that considers AS seed poisoning based on a Langmuir adsorption isotherm. The degree of AS removal after lime treatment increased linearly with the logarithm of the single lime dose additions. Staged lime dosing (i.e., multiple lime additions), however, removed a higher degree of AS relative to an equivalent single lime dose addition since a higher driving force for CaCO3 precipitation could be maintained over the course of the lime treatment period.

Experiences with pellet reactor softening as pretreatment for inland desalination in the USA

A high water recovery is important in inland desalination. In the nineteen eighties projects in Saudi Arabia applied a treatment train consisting of pellet softening, rapid filtration, RO, brine concentrators and evaporation ponds to achieve zero liquid discharge. In the past few years AwwaRF sponsored research on Zero Liquid Discharge for Inland Desalination. This research was completed in 2007 and concluded that pellet softening was the preferred treatment process of primary RO concentrate to allow subsequent treatment of this concentrate in a secondary RO. Since then a number of projects have been started based on this treatment principle. Interesting findings are that 1. Softening or desalination of drinking water can significantly reduce the chloride discharge in waste water, because it results in a reduction of the salt usage for self regenerating ion exchange softeners; 2. Pellet softening not only reduces the concentrations of calcium and hydrogen carbonate, but can achieve a significant removal of silica as well. Use of pellet softening can improve the economic and technical feasibility of inland desalination.

High recovery membrane desalting of low-salinity brackish water: Integration of accelerated precipitation softening with membrane RO

The integration of membrane RO desalting and accelerated precipitation softening (APS) was evaluated for achieving high product water recovery (>95%) from desalting of mildly brackish surface water. A systematic approach that included laboratory RO demonstrations, membrane scaling diagnostics, and mineral solubility analysis was undertaken to develop an effective physical/chemical APS strategy for reducing the concentration of scale-forming ions in the primary RO (PRO) concentrate. APS demineralization, as an inter-stage process, between the PRO and secondary RO (SRO) desalting, involved alkaline pH adjustment and calcite crystal seeding of the PRO concentrate, followed by microfiltration and pH reduction by acid dosing to avoid calcite scaling in the SRO stage. Colorado River water desalting case study demonstrated that, at 90% PRO recovery, the PRO concentrate stream contained barite, calcite, gypsum, and silica above their solubility limits by factors of 122, 47, 1.1, and 0.8, respectively. Further desalting was not feasible with traditional scale-control strategies (e.g., pH reduction and antiscalant addition). However, APS demineralization enabled significant concentration reduction of calcium (>90%), barium (>95%), and strontium (∼78%) and moderate reduction (10–20%) of magnesium and silica. APS kinetics were favorable even in the presence of antiscalant carryover from the PRO stage. The study demonstrated that high recovery desalination of up to 98% is feasible with the PRO-APS-SRO sequence, which reduces the limitations imposed by membrane scaling.

Pharmacokinetic aspects of sulfobromophthalein transport in chronically carbon tetrachlorideintoxicated rats

In order to elucidate the factors affecting the hepatic transport of sulfobromophthalein (BSP) in a pathological condition, the kinetics of the disappearance of BSP from the blood and appearance in the bile were studied in rats chronically intoxicated with carbon tetrachlorde, and the importance of factors that might affect the kinetics, i.e. binding activites of plasma and hepatic cytoplasmic proteins, and glutathione S-transferase activity of Y-fraction, was examined. During chronic intoxication, although plasma protein albumin concentration decreased, no qualitative difference was shown in the high affinity binding site ( K 1). A significant decrease was shown in the cytoplasmic protein concentration for the Y- and Z-fractions in intoxicated rats; no significant difference was observed in the number of binding sites for both fractions, but their binding constants decreased. Glutathione S-transferase activity and glutathione (GSH) content were not altered, although a decrease in conjugating activity per rat was expected. The time course for the plasma disappearance and biliary excretion of BSP showed a remarkable delay after CCl 4 intoxication, while no difference was shown in the bile flow rate. It was concluded that hepatic blood flow might play a primary ro)e in the initial plasma disappearance of BSP and that the decrease in the Y-fraetion binding activity might explain the decrease in BSP uptake rate into the liver which was observed in intoxicated rats.