Pilot-scale Field Experiments Research Articles

Effect of rice husk addition on the physicochemical and hydrological properties on green roof substrates under subtropical climate conditions

Green roof substrates provide water, nutrients, and physical support to vegetation development, as well as being a key element in the hydrological performance of the system. In this regard, the use of aggregate components that improve physicochemical properties of the substrates optimises the ecosystem services provided by green roofs. This study demonstrates the effects of using rice husk as an aggregate material in engineered substrates for extensive green roofs. Sixteen different substrates compositions were tested with different proportions of natural (NRH) and carbonized (CRH) rice husk incorporated into a base mixture with fixed proportions of vermicompost, vermiculite, and construction waste. The study consists of two phases: i) laboratory analyses to assess the substrates' physicochemical properties, and ii) a pilot-scale field experiment to evaluate hydrological performance under real subtropical climate conditions and vegetation development using a monoculture planting of Sedum rupestre. The findings showed that CRH has the potential to improve some physicochemical properties, such as water holding capacity, bulk density, and porosity. Additionally, CRH substrates presented a slightly increased average retention rate (up to 7%) comparing to local topsoil. The average stormwater retention rate for all engineered substrates was 77.73%. Multiple linear regression models were satisfactorily fitted to observed data from the open field experiment allowing an estimation of potential substrates’ retention rates. Moreover, vegetation development was positively affected by adding CRH comparing to the NRH. Carbonized rice husk presents as a useful material for improving green roof substrates properties and could be a sustainable alternative for local agriculture waste management.

A field-scale remediation of residual light non-aqueous phase liquid (LNAPL): chemical enhancers for pump and treat

The remediation of petroleum-contaminated soil and groundwater is a challenging task. The petroleum hydrocarbons have a long persistence in both the vadose zone and in the aquifer and potentially represent secondary and residual sources of contamination. This is particularly evident in the presence of residual free-phase. Pump-and-treat is the most common hydrocarbon decontamination strategy. Besides, it acts primarily on the water dissolved phase and reduces concentrations of contaminants to an asymptotic trend. This study presents a case of enhanced light non-aqueous phase liquid (LNAPL) remediation monitored using noninvasive techniques. A pilot-scale field experiment was conducted through the injection of reagents into the subsoil to stimulate the desorption and the oxidation of residual hydrocarbons. Geophysical and groundwater monitoring during pilot testing controlled the effectiveness of the intervention, both in terms of product diffusion capacity and in terms of effective reduction of pollutant concentrations. In particular, non-invasive monitoring of the reagent migration and its capability to reach the target areas is a major add-on to the remediation technique. Most of the organic contaminants were decomposed, mobilized, and subsequently removed using physical recovery techniques. A considerable mass of contaminant was recovered resulting in the reduction of concentrations in the intervention areas.

Newly developed membrane contactor-based N and P recovery process: Pilot-scale field experiments and cost analysis

In this study, a newly developed nitrogen (N) and phosphorus (P) recovery process using a membrane contactor termed NPHarvest was tested with different liquid waste streams in large-scale trials. Ammonia was captured in ammonium sulfate form using a hydrophobic membrane, while phosphorus was precipitated as sludge using alkali precipitation and coagulation processes. The tested streams were selected to cover the potential liquid waste streams for nitrogen recovery and included two different mesophilic digester reject waters, landfill leachate, and separately collected urine. The NPHarvest pilot was tested with hydraulic loads in the range of 12–133 L/h. Nitrogen recovery efficiency reached a maximum of 92.5% with the reject water of mesophilic digester and a maximum ammonia flux of 481.1 mg/L.h was obtained with a urine stream. A mass transfer coefficient was calculated for the four tested wastewater streams using two different approaches, resulting in two value ranges in the order of 10−3 and 10−7 m/s. It was found that the mass transfer coefficient decreased with increase in the initial nitrogen concentration. The recovery of phosphorus varied between 79% and 97%. The quality of ammonium sulfate was evaluated by employing comprehensive tests that included vegetative cells and coliphages, harmful metals, and organic micropollutant measurements. These measurements confirmed that ammonium sulfate meets the Finnish legislation requirements for agricultural use. The use of a diluted acid wash was proven to be sufficient for maintaining membrane surface properties and was confirmed by the observed insignificant loss of hydrophobicity and the mild development of fouling. Finally, the competitiveness of NPHarvest compared to existing processes was confirmed through a detailed cost analysis.

Laboratory and pilot-scale field experiments for application of iron oxide nanoparticle-loaded chitosan composites to phosphate removal from natural water

ABSTRACTThe aim of this study was to apply iron oxide nanoparticle-chitosan (ION-chitosan) composites to phosphate removal from natural water collected from the Seoho Stream in Suwon, Republic of Korea. Laboratory batch experiments showed that phosphate removal by the ION-chitosan composites was not sensitive to pH changes between pH values of 5.0 and 9.0. During six cycles of adsorption–desorption, the composites could be successfully regenerated with 5 mM NaOH solution and reused for phosphate removal. Laboratory fixed-bed column experiments (column height = 10 and 20 cm, inner diameter = 2.5 cm, flow rate = 8.18 and 16.36 mL/min) demonstrated that the composites could be successfully applied for phosphate removal under dynamic flow conditions. A pilot-scale field experiment was performed in a pilot plant, which was mainly composed of chemical reactor/dissolved air flotation and an adsorption tower, built nearby the Seoho Stream. The natural water was pumped from the Seoho Stream into the pilot plant, passed through the chemical reactor/dissolved air flotation process, and then introduced into the adsorption tower (height = 100 cm, inner diameter = 45 cm, flow rate = 7.05 ± 0.18 L/min) for phosphate removal via the composites (composite volume = 80 L, composite weight = 85.74 kg). During monitoring of the adsorption tower (33 days), the influent total phosphorus (T-P) concentration was in the range of 0.020–0.046 mgP/L, whereas the effluent T-P concentration was in the range of 0.010–0.028 mgP/L. The percent removal of T-P in the adsorption tower was 52.3% with a phosphate removal capacity of 0.059 mgP/g.

Remediation of High Arsenic Aquifers by Learning from the Nature

Almost 20 years’ multi-disciplinary study on geogenic high arsenic (As) groundwater systems in China has greatly improved our understanding of the major processes controlling hydrogeochemical behavior of As in the subsurface environment. Among them, sorption by Fe(III) oxide/hydroxides was found to be one of the dominant processes retaining As in the aquifer matrix. Managed Aquifer Rehabilitation (MAR) by enhancing Fe(II) oxidation to promote As sorption was proposed and tested in a pilot-scale field experiment. Periodical injection of Fe(II) and ClO− into a high As sandy aquifer triggered formation of new Fe(III) (hydr)oxides coating on sediment particles via advanced heterogeneous oxidation of Fe(II) and concurrent oxidative adsorption of As(III) via co-precipitation and surface complexation with Fe(III) (hydr)oxides. Monitoring results indicate that aqueous As concentration decreased from the initial average value of 78.0μg/L to 9.8μg/L over the 25-day amendment period and leveled off below 10μg/L for the following 30 days. MAR is thus proved to be a cost-effective approach for remediating high As aquifers.

Effects of vegetation on ammonium removal and nitrous oxide emissions from pilot-scale drainage ditches

Recently, vegetated drainage ditches have been used as one of the best management practices for controlling the transport of agricultural pollutants. In this study, a pilot-scale field experiment within a 135-km2 agricultural catchment was conducted to investigate the effectiveness of ditches vegetated with Pontederia cordata (Pontederia) and Myriophyllum elatinoides (Myriophyllum) and ditches without vegetation (Control) on ammonium (NH4+-N) removal and nitrous oxide (N2O) emissions. Compared to the control treatment, the ditches with both plant species (P. cordata and M. elatinoides) increased NH4+-N removal rates by 50.8% and 71.4% and decreased N2O emissions by 68.3% and 70.4% for NH4+-N loadings of 25mgL−1 and 70mgL−1, respectively. The linear mixed-effect model revealed that effluent NH4+-N concentrations were significantly decreased by 2.54% and 2.10% for each increase of one unit on sediment NH4+-N sorption and plant TN accumulations (p<0.0001). The dominant NH4+-N removal pathways in Myriophyllum ditch were plant uptake and microbial nitrification-denitrification. However, in Pontederia and control ditches, NH4+-N was mainly removed by sediment sorption. These findings may suggest that vegetated drainage ditches (e.g., M. elatinoides) are capable of removing NH4+-N from agricultural runoff and can additionally reduce N2O emissions.

Dynamic Succession of Groundwater Functional Microbial Communities in Response to Emulsified Vegetable Oil Amendment during Sustained In Situ U(VI) Reduction.

A pilot-scale field experiment demonstrated that a one-time amendment of emulsified vegetable oil (EVO) reduced groundwater U(VI) concentrations for 1 year in a fast-flowing aquifer. However, little is known about how EVO amendment stimulates the functional gene composition, structure, and dynamics of groundwater microbial communities toward prolonged U(VI) reduction. In this study, we hypothesized that EVO amendment would shift the functional gene composition and structure of groundwater microbial communities and stimulate key functional genes/groups involved in EVO biodegradation and reduction of electron acceptors in the aquifer. To test these hypotheses, groundwater microbial communities after EVO amendment were analyzed using a comprehensive functional gene microarray. Our results showed that EVO amendment stimulated sequential shifts in the functional composition and structure of groundwater microbial communities. Particularly, the relative abundance of key functional genes/groups involved in EVO biodegradation and the reduction of NO3 (-), Mn(IV), Fe(III), U(VI), and SO4 (2-) significantly increased, especially during the active U(VI) reduction period. The relative abundance for some of these key functional genes/groups remained elevated over 9 months. Montel tests suggested that the dynamics in the abundance, composition, and structure of these key functional genes/groups were significantly correlated with groundwater concentrations of acetate, NO3 (-), Mn(II), Fe(II), U(VI), and SO4 (2-). Our results suggest that EVO amendment stimulated dynamic succession of key functional microbial communities. This study improves our understanding of the composition, structure, and function changes needed for groundwater microbial communities to sustain a long-term U(VI) reduction.

A Metal Sorption/Desorption Study to Assess the Potential Efficiency of a Tailings Dam at the Golgohar Iron Ore Mine, Iran

The Golgohar Iron Ore Mine in southern Iran is a large open pit that operates below the groundwater table; until now, its tailings have been disposed of without proper environmental safeguards. A tailings dam, constructed with environmental standards, has been proposed to address this problem. So, it was important to assess the effect of the solid and liquid wastes on the sorption/desorption behavior of the soil of the site to evaluate the risk of release of metal contaminants to groundwater after dam construction. Soil samples from a proposed tailings dam reservoir site and dried solid waste from the present tailings dump were collected for analysis to assess the potential effects of solid and liquid wastes on the sorption/desorption behavior of the soil and the risk of resultant groundwater contamination after dam construction. Laboratory batch and sorption isotherm tests along with a pilot-scale field experiment were conducted to study the sorption potential of the soil. Analysis showed that concentrations of Co, Ni, Cu, As, Sr, and Mn in the soils were already significantly elevated. The experiments indicated that although the soil of the area has some potential to adsorb contaminants such as Co, Ni, Cu, and As, other elements, such as Sr and Mn will be more mobile. Given the soil’s limited sorption capacity, these contaminants will all likely enter the groundwater eventually, and so the probable transmission of these elements into the lower depths must be considered in the design of the proposed dam.

Formation of a hardpan in the co-disposal of fly ash and sulfide mine tailings and its influence on the generation of acid mine drainage

Pilot-scale field experiments were conducted to test a strategy for the treatment of acid mine drainage by addition of an alkaline cover of coal combustion fly ash on two sulfide mine tailings impoundments (Iberian Pyrite Belt, SW Spain). During the pilot-scale treatment, calcium-rich alkaline solutions from fly ash interacted with metal-rich acidic solutions from the mine tailings, leading to the massive precipitation of newly-formed phases mainly in the fly ash close to the interface between both materials. Over time, the interaction between fly ash and pyrite sludge promoted the formation of a chemically cemented zone or hardpan, which was analyzed at high spatial resolution by micro-X-ray diffraction (μ-XRD) and micro-X-ray fluorescence (μ-XRF) based on synchrotron radiation. These micro-characterization techniques extensively identified poorly-crystalline Fe oxyhydroxysulfates, jarosite and gypsum as newly-formed phases in the hardpan, and gypsum in the fly ash. As deduced from Principal Component Analysis of the fluorescence intensity data, these phases seem to exert a significant mineralogical control on element mobility; in particular, jarosite showed high affinity for As, whereas poorly-crystalline Fe-rich assemblages selectively concentrated Mn, Ni and Pb. Sequential extractions indicated that the application of a fly ash cover significantly reduced the bioavailability of most of the elements by modification of their chemical speciation into less mobile forms under typical oxidizing conditions. As an additional advantage, the development of the hardpan hindered the penetration of oxidizing agents to sulfide mine tailings. This effect significantly reduced the sulfide oxidation rates, therefore attenuating the release of potentially pollutant elements to the environment.

Enhanced resolution for long electrode ERT

SUMMARY The resolution of the long electrode electrical resistivity tomography method is investigated through the comparison of arrays. The investigations included a synthetic model study and a pilot-scale field experiment, in which data from the 2-pole and 4-pole arrays were used to reconstruct known targets through inverse modelling. The results confirmed that the 2-pole array maps conductive targets with low lateral resolution and no vertical resolution. The 4-pole array performs extremely well or extremely poorly depending on the specific subset of data used in the inversion modelling. The worst performance was observed from using a randomized 4-pole subset. In this case, the reconstructed target was offset from the known location. The best performance came from evaluating the comprehensive data set comprising all possible 4-pole combinations and choosing favourable subsets that minimized outliers in transfer resistance, geometric factor, data error and apparent resistivity. These favourable 4-pole subsets were capable of resolving both conductive and resistive targets with higher fidelity than the 2-pole array. Unfortunately, it may not be possible to acquire the comprehensive 4-pole data set, especially for a large number of electrodes. A viable alternative is to acquire the comprehensive 2-pole data set and calculate any desired 4-pole subset using superposition. In this way, the geophysicist will also have full advantage of signal strength and shorter measurement cycle that accompanies the 2-pole array.

A pilot-scale field experiment for the microbial neutralization of a holomictic acidic pit lake

A strategy to neutralize acidic pit lakes was tested in an upscaling process using field mesocosms of 26 to ca. 4500 m 3 volume in the acidic pit Mining Lake 111 in Germany. After addition of the substrates Carbokalk and straw a neutral sediment layer formed, in which microbial sulfate and iron reduction as well as sulfide precipitation occurred. The net rate of neutralization was limited by the precipitation of iron sulfides rather than by microbial reactions. Oxidation of H 2S by ferric iron in the anoxic sediment lowered the net sulfate reduction rate. Seasonal fluctuations of iron sulfides in the sediment showed that the reaction products were not necessarily stable. The long-term success of the approach depends on the net partition of the precipitated iron-(mono-/di-) sulfide that is permanently buried in the anoxic sediment. It could be shown by field experiments that the long-term success of the neutralization depends on the spatial scale and duration of the experiments. Volumes from 26 to 4500 m 3, exposition times from 4 months to 5 years, and increasingly thick coverings of the sediments with straw, from zero to 40 cm, were used. Net neutralization rates decreased from 41 meq m − 2 d − 1 in laboratory microcosms to a mean rate of 2.3 meq m − 2 d − 1 in the 4500 m 3 field experiment. The results show that the success of the microbial treatment of acid pit lakes lastly depends on the limnological conditions in the lake that cannot be simulated by upscaling of simple laboratory experiments.

Biodegradation of cyclodextrins in soil

Cyclodextrins, especially random methylated βCD (RAMEB) and hydroxypropyl βCD (HPβCD), are becoming common enhancing additives in the bioremediation of soils formerly contaminated by hydrocarbons and/or other poorly bioavailable organic pollutants. Therefore, their degradation in the soil, particularly the most persistent RAMEB, has been of great concern. Like oil contaminants, these additives should be biodegradable via an environmentally safe technology. Hence, in this paper, the biodegradability of eight different cyclodextrins (CDs) in four different soils was examined under various treatment conditions in laboratory and pilot scale field experiments. This paper is the first report on the potential biological fate of CDs studied under a large variety of environmental conditions and in different soil ecosystems. Data on the potential relationship between CD biodegradation and the biological removal of hydrocarbons in the CD-amended contaminated soils are also given. All CDs were found to be more or less biodegradable; even the most persistent RAMEB was depleted from soils under favourable conditions. In the field experiments, the depletion of RAMEB to about 40% of its initial level was observed for a period of 2 years in hydrocarbon-contaminated soils of high organic matter and cell concentration.

Nutrient removal from farm effluents

The objectives of the study were: (i) to examine the efficiency of nutrient removal during the treatment of dairy farm effluent in a two-pond system, and (ii) to produce an inexpensive but effective nutrient trap which could be recycled as a nutrient source or soil mulch. The concentration of chemical oxygen demand (COD), biological oxygen demand (BOD), nitrogen (N), phosphorus (P) and potassium (K) in a two-pond system used to treat dairy farm effluent was monitored over a period of 7 months. The retention of nutrients by two porous materials was examined both in the laboratory batch (zeolite and bark) and pilot-scale field (bark) experiments. The results indicated that biological treatment of farm effluents using the two-pond system was not effective in the removal of nutrients, which are likely to become pollutant when discharged to waterways. Both the bark and zeolite materials were effective in the removal of N, P and K from effluent. These materials can be placed in the second (i.e., aerobic) pond to treat effluents, which can then be discharged to streams with minimum impact on water quality. The nutrient-enriched porous materials can be recycled as a source of nutrients and soil conditioner.

Phosphate-induced metal immobilization in a contaminated site

To assess the efficiency of P-induced metal immobilization in soils, a pilot-scale field experiment was conducted at a metal contaminated site located in central Florida. Phosphate was applied at a P/Pb molar ratio of 4.0 with three treatments: 100% of P from H 3PO 4, 50% of P from H 3PO 4+ 50% of P from Ca(H 2PO 4) 2, and 50% of P from H 3PO 4+5% phosphate rock in the soil. Approximately 1 year after P application, soil and plant samples were collected to determine mobility and bioavailability of selected metals (Pb, Zn, and Cu) using sequential extraction procedure and mineralogical characterization using X-ray diffraction (XRD) and scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis. Phosphorus distribution and soil pH effects were also evaluated. Phosphate was more effective in transforming soil Pb (to 53%) from the non-residual to the residual phase than soil Zn (to 15%) and soil Cu (to 13%). This was because Pb was immobilized by P via formation of an insoluble pyromorphite-like mineral in the surface and subsurface of the soil, whereas no phosphate mineral Zn or Cu was identified. While P amendment enhanced metal uptake in the roots of St. Augustine grass ( Stenotaphrum secundatum), it significantly reduced metal translocation from root to shoot, especially Pb via formation of a pyromorphite-like mineral on the membrane surface of the root. A mixture of H 3PO 4 and phosphate rock was effective in metal immobilization, with less soil pH reduction and less soluble P. Although H 3PO 4 was effective in immobilizing Pb, its use should be limited to minimize soil pH reduction and potential eutrophication risk.

Vitamin B12 and Reduced Titanium for Remediation of Residual Chlorinated Solvents: Field Experiment

AbstractA first pilot‐scale field experiment using vitamin B12 and reduced titanium was conducted in an in situ vertical circulation column at CFB Borden. The objective of the experiment was to test the applicability of the technology for restoring aquifer source zones contaminated by chlorinated solvents—tetrachloroethene (PCE) and 1,1,1‐trichloroethane (1,1,1‐TCA)—in a mixture of dense nonaqueous phase liquids (DNAPLs). Vitamin B12 promotes the reductive dechlorination of chlorinated organics. A highly reducing and slightly alkaline environment must be maintained (Eh &lt; ‐ 480 mV and 7 &lt; pH &lt; 9) to maximize the rate of degradation. In this field test, PCE and 1,1,1‐TCA degraded to a limited extent under experimental conditions, with 1,1,1‐TCA degrading more readily. Indigenous bacteria were found to metabolize citrate, which caused titanium to precipitate, limiting degradation. The addition of glucose at the end of a second field season effectively limited citrate degradation and helped recover the optimal redox potential by keeping reduced titanium in solution. A laboratory column was used to confirm field results. The column also produced a significant biomass, which provided an additional source of organic carbon onto which the solvents sorbed.

Prevention of Acidic Groundwater in Lignite Overburden Dumps by the Addition of Alkaline Substances: Pilot-scale Field Experiments

Mining activities in the Rhineland lignite mining area in Germany have led to increased mineralisation and acidity of groundwater due to the oxidation of sulfide minerals. The potential benefit of adding alkaline substances (crushed limestone and a mixture of fly ash and crushed limestone) to the overburden spoil was investigated using laboratory columns and pilot-scale field experiments. The latter tests were each conducted with 13 metric tons of overburden. A considerable improvement in water quality (decreased sulfate, iron, trace elements and acidity) was found in both scales of experiment. Similar improvements are expected in the limed overburden dump of the Garzweiler lignite mine.

Practical Aspects of In-Situ Electrokinetic Extraction

Electrokinetic extraction in an emerging technology that can be used to remove contaminants from heterogeneous fine-grained soils in situ. Contaminants in the subsurface are removed by the application of a direct-current electric field across the contaminated soil. The primary contaminant transport and removal mechanisms are electroosmotic advection and ionic migration. However, there are many complex physicochemical reactions occurring simultaneously during the process that may enhance or retard the cleanup process. Nonetheless, the viability of the technology has been established by results obtained from many bench-scale and large-scale laboratory and pilot-scale field experiments performed on various soils. This paper will review the fundamental concepts of the technology and discuss some important practical aspects and design criteria of the technology for field implementations. An example on cost analysis of the technology is also presented to demonstrate the use of various equations presented in the paper and to illustrate the cost-effectiveness of the technology.

Large-scale application of UF and RO in the production of demineralized water

The water demineralization plant in Geleen (NL) for the production of boiler feed water from surface water with a maximum plant capacity of 1560 m 3/h uses reverse osmosis (RO) as the basic process step for desalination. In order to ensure maximum operational reliability of the RO, a dead-end ultrafiltration (UF) pretreatment step is used, giving the best feed quality with respect to RO fouling behaviour. In order to enable a proper design of the UF, a series of pilot-scale field experiments were carried out on-site. The overall process design, the experimental results of those experiments and the resulting selection of a suitable UF membrane are described. The subsequent selection of a suitable RO membrane for the process is then largely determined by economic aspects, which may be deduced from the membrane properties, representatively expressed in terms of salt passage and water flux (or required feed pressure) of the respective membrane.

In situ remediation of petroleum compounds in groundwater aquifer with chlorine dioxide

A comparison was made of the remedial effect on organic contaminants using ozone, chlorine dioxide, potassium permanganate and hydrogen peroxide in laboratory tests. Chlorine dioxide was chosen for use in in situ remediation of a petroleum contaminated aquifer. The laboratory experiments indicated that oxidation capacity of chlorine dioxide was affected by reaction time, gas injection method, and pH of groundwater. A pilot-scale field experiment was conducted through the oxidation treatment involving the injection of chlorine dioxide solution into the aquifer where pollutants included more than 80 organic compounds containing 14 mutagens. The in situ oxidation treatment proved that most of the organic contaminants including 5 mutagenic compounds were decomposed or removed and 19 new by-products were found without mutagenic carcinogens. The results shows that the unsaturated hydrocarbons were easily removed excluding that some of saturated alkane and alkene and polycyclic aromatic hydrocarbons and heterocyclic compounds were not oxidizable. The oil concentration in groundwater reduced by 50–60%. It was evident that desorption of organic contaminants from aquifer media significantly affected the groundwater quality during remediation process. Therefore, groundwater remediation must include aquifer media cleaning.