Roger C. Viadero

Membrane filtration for removal of fine solids from aquaculture process water

Abstract In recirculating aquaculture systems (RASs), fine solids (diameters 94% TSS rejection and 76% biochemical oxygen demand rejection. In cross-flow membrane filtration using a 0.05 μm pore size hollow fiber membrane, permeate flux increased with increasing feed temperature. Flux also increased with and transmembrane pressure up to a limit after which a pressure independent flux was observed. On average, pressure independent flux was found to increase with cross-flow rate approximately linearly. Based on a preliminary assessment of process economics, it was determined that membrane filtration was not a cost effective alternative to coarse solids removal processes such as microscreen clarification. However, membrane filtration for fine solids removal has potential niche applications in areas such as rearing high-value products.

Study of series resistances in high-shear rotary ultrafiltration

A parametric waste-specific study was conducted to determine the relationship between permeate flux, transmembrane pressure, membrane rotational speed, and feed concentration in the high-shear rotary ultrafiltration (HSRUF) of a synthetic metal working (MW) fluid. The interactions between permeate flux and operating parameters were described using the resistance-in-series (RIS) approach to flux modeling. Eighteen discrete experiments were conducted at constant MW fluid concentration/membrane rotational speed combinations at applied pressures ranging from 103 to 517 kPa (15 to 75 psig). The fouling layer resistance, Rf, was only 12% of the total membrane resistance, R 0 , and it was determined that Rf and R 0 were independent of feed concentration and membrane rotational speed. The polarization layer resistance, Rp, was the predominant rate controlling resistance in the HSRUF of the synthetic MW fluid; however, membrane rotation induced hydraulic turbulence was effective in minimizing Rp by reducing the accumulation of solute molecules on the membrane surface. An explicit form of the resistance index, , was postulated based upon observations of interactions between , feed MW fluid concentration, and membrane rotational speed. The RIS model was then modified with a specific form of to further describe the specific interactions between flux and operating parameters. The modified model adequately predicted flux‐pressure data over the range of experimental variables examined in this study. Additionally, a set-point operating pressure was determined as a function of membrane rotational speed and feed oil concentration such that the resistances R 0 and Rp were minimized. # 1999 Elsevier Science B.V. All rights reserved.

Two-phase limiting flux in high-shear rotary ultrafiltration of oil-in-water emulsions

A study was conducted to assess the effect(s) of high oil concentration on the pressure-independent ‘limiting’ permeate flux and the ability of a thin film model to adequately predict the flux in the treatment of synthetic and waste metal working fluids using the high-shear rotary ultrafiltration (HSRUF) system. Two distinct limiting flux regions were ascertained, in contrast to a discrete flux decline with concentration predicted from the thin film model. Additionally, widely different gel layer oil concentrations were predicted based on data from each discrete region. Thus, it was not possible to predict the occurrence of the two-phase limiting flux or the closest packed arrangement of emulsified oil droplets using a thin film model. The net effect of the unique ‘wagon wheel’ turbulence promoters was to enhance hydraulic turbulence in the HSRUF system; thus, the transition from laminar to turbulent hydraulic flow occurred at lower Rer in the HSRUF system than reported previously for a solid plate turbulence promoter. Further, it was demonstrated that the occurrence of the two-phase limiting flux resulted in operating conditions under which high feed oil concentrations could be attained while maintaining acceptable limiting flux.

Effects of highway construction on stream water quality and macroinvertebrate condition in a Mid-Atlantic Highlands watershed, USA.

Refining best management practices (BMPs) for future highway construction depends on a comprehensive understanding of environmental impacts from current construction methods. Based on a before-after-control impact (BACI) experimental design, long-term stream monitoring (1997-2006) was conducted at upstream (as control, n = 3) and downstream (as impact, n = 6) sites in the Lost River watershed of the Mid-Atlantic Highlands region, West Virginia. Monitoring data were analyzed to assess impacts of during and after highway construction on 15 water quality parameters and macroinvertebrate condition using the West Virginia stream condition index (WVSCI). Principal components analysis (PCA) identified regional primary water quality variances, and paired t tests and time series analysis detected seven highway construction-impacted water quality parameters which were mainly associated with the second principal component. In particular, impacts on turbidity, total suspended solids, and total iron during construction, impacts on chloride and sulfate during and after construction, and impacts on acidity and nitrate after construction were observed at the downstream sites. The construction had statistically significant impacts on macroinvertebrate index scores (i.e., WVSCI) after construction, but did not change the overall good biological condition. Implementing BMPs that address those construction-impacted water quality parameters can be an effective mitigation strategy for future highway construction in this highlands region.

Use of treated mine water for rainbow trout (Oncorhynchus mykiss) culture—a preliminary assessment

Treated waters from active and abandoned coal mines are a potentially valuable, though underutilized resource, which may be used to expand the aquaculture industry in West Virginia and other mid-Appalachian states. A preliminary investigation of the technical feasibility of using treated acid mine waters to rear rainbow trout (Oncorhynchus mykiss) was conducted. In the study, a regimen of water quality monitoring was initiated to fully characterize a treated mine water and allow for comparison with requirements for salmonid culture. To complement water quality studies, a bioassay consisting of fifty rainbow trout were grown in a net pen in the treated mine water; production-scale studies were not the focus of this initial work. Although aqueous phase concentrations of metals associated with acid mine drainage (AMD) (Fe, Al, Mn, Ca, Mn) often exceeded limits recommended for salmonid culture, the fish grew and exhibited no physiological signs of stress. The lack of anticipated water quality impacts on the fish was attributed to a combination of the effects of high ionic strength on the chemical activity of dissolved metal species and the formation of dissolved metal–ligand pairs in the treated mine waters. Thus, non ideal effects of high ionic strength and the coordination chemistry of treated mine waters must be considered when assessing the suitability of such waters for aquaculture, as many water resources otherwise considered too impaired for aquaculture use may be rendered viable.

Structural and functional aspects of treated mine water and aquaculture effluent streams

Multiple effluent streams may flow into a single receiving stream making it difficult to understand the effects of a single effluent source or the interactions between effluents. In this study, we examined benthic community structure and function in an effluent stream formed by the release of treated mine water, in treated mine water that had been used as a water source for flow-through aquaculture and below the confluence of the two. This study demonstrated that macroinvertebrate communities, while taxonomically simple, developed in treated mine water. The addition of aquaculture effluent to the treated mine water allowed colonization by additional taxa, increased leaf decomposition rates and may have conferred resistance to a turbidity event. Ecosystem responses were mediated by the surrounding terrestrial environment. In shaded conditions macroinvertebrate densities could be as much as 10× higher and the taxa were dominated by simuliids and chironomids, while in open conditions filamentous algae flourished and the taxa were dominated by hydroptilids and chironomids. Consequently, consideration of stream processes that promote preferred ecological processes, such as macroinvertebrate production and organic matter processing, when siting effluent streams may reduce impacts on receiving streams.

Water-Quality Assessment and Environmental Impact Minimization for Highway Construction in a Miningimpacted Watershed: The Beaver Creek Drainage

Abstract Beaver Creek, a tributary of the Blackwater River just north of Canaan Valley in northeastern West Virginia, runs parallel to the proposed alignment of a major four-lane highway called Appalachian Corridor H. Beaver Creek and many of its major tributaries are characterized by low pH, little alkalinity, and high levels of dissolved metals due to the geochemical characteristics of the soils parent material and continuing impacts from past coal mining. During the planning phase of this road project, we identified two major environmental concerns: (1) our ability to predict and manage water-quality impairments that will likely result from the cuts and fills of new material, and (2) the legacy effects of mine refuse from historic coal mines. In the latter case, although many refuse sites are located outside the proposed highways alignment, drainage from these sites will be intercepted by the highways water-control structures. We (West Virginia University [WVU]) have collaborated with the West Virginia Division of Highways (WVDOH) to minimize construction-related impacts to Beaver Creeks water quality. More specifically, we have evaluated strategies by which water collection and conveyance structures can be integrated with passive water-remediation processes during the highways design and construction. In March 2000, we began monitoring water quality in the Beaver Creek drainage. We measured physical, chemical, and biological indicators of water quality and present these data here to serve as a baseline for future comparisons. In general, the water in Beaver Creek was acidic with an average pH of 5.1 in its headwaters and 6.1 above its confluence with the Blackwater River. The water also carried little or no alkalinity. The untreated water seeping from mine-waste piles was highly acidic, with an average pH of 3.0, carried high levels of dissolved sulfate and iron, and featured excess acid-production capacity. After we identified the main sources of water-quality impairment—the locations of mine-waste piles and acidic seeps—we formulated preliminary recommendations for minimizing the impacts of highway construction on the Creeks water quality. For example, we recommended the implementation of acid-base accounting on the overburden that would be disturbed during construction. We also suggested special material-handling procedures. Based on our preliminary water-quality data, we recommended a series of passive treatment processes that could be incorporated into the roads design, construction, and operation. Future treatment decisions will be informed by our growing dataset. Further, because many sources of water-quality impairment are located within the basin but beyond the roads proposed alignment, efforts must be made to engage diverse stakeholders to leverage support for protecting and restoring the Beaver Creek watershed.

Microfiltration of a Dental Wastewater (DWW) for Hg Removal

A tubular membrane (MWCO = 200 k, PVDF, negative surface charge) and a hollow-fiber (HF) membrane (MWCO = 500 k, PS, neutral surface charge) underwent testing to determine their effectiveness in treating a sterilized wastewater from a dental clinic. The tubular membrane, which had a lower MWCO, produced a higher permeate flux due to the increased turbulence at the membrane surface that was possible with the tubular configuration (Reynolds numbers for the tubular module were over five times greater than the HF module). Both membranes had similar Hg rejections (tubular - 97%, HF - 98%) and permeate Hg concentrations (≤10 μg/L) due to particle size distribution of dental wastewater - the vast majority of the amalgam particles were larger than the pore size of either membrane. Permeate Hg was not a function of temperature, feed concentration, and intermittent operation. Because of their unique behavior and characteristics, both the HF and tubular modules will be tested at an actual dental clinic using non-ste...