Road Deicing Research Articles

Improvement of acetate production from lactose by growing Clostridium thermolacticum in mixed batch culture.

The objective of this study was to increase the acetate production by Clostridium thermolacticum growing on lactose, available as a renewable resource in the milk and whey permeate from the cheese industry. Experiments for increased acetate productivity by thermophilic anaerobes grown on lactose were carried out in batch cultures. Lactose at concentration of 30 mmol l(-1) (10 g l(-1)) was completely degraded by Cl. thermolacticum and growth rate was maximal. High concentrations of by-products, ethanol, lactate, hydrogen and carbon dioxide were generated. By using an efficient hydrogenotroph, Methanothermobacter thermoautotrophicus, in a defined thermophilic anaerobic consortium (58 degrees C) with Cl. thermolacticum and the acetogenic Moorella thermoautotrophica, the hydrogen partial pressure was dramatically lowered. As a consequence, by-products concentrations were significantly reduced and acetate production was increased. Through efficient in situ hydrogen scavenging in the consortium, the metabolic pattern was modified in favour of acetate production, at the expense of reduced by-products like ethanol. The use of this thermophilic anaerobic consortium opens new opportunities for the efficient valorization of lactose, the main waste from the cheese industry, and production of calcium-magnesium acetate, an environmentally friendly road de-icer.

Assessing the validity of road safety evaluation studies by analysing causal chains

This paper discusses how the validity of road safety evaluation studies can be assessed by analysing causal chains. A causal chain denotes the path through which a road safety measure influences the number of accidents. Two cases are examined. One involves chemical de-icing of roads (salting). The intended causal chain of this measure is: spread of salt → removal of snow and ice from the road surface → improved friction → shorter stopping distance → fewer accidents. A Norwegian study that evaluated the effects of salting on accident rate provides information that describes this causal chain. This information indicates that the study overestimated the effect of salting on accident rate, and suggests that this estimate is influenced by confounding variables the study did not control for. The other case involves a traffic club for children. The intended causal chain in this study was: join the club → improve knowledge → improve behaviour → reduce accident rate. In this case, results are rather messy, which suggests that the observed difference in accident rate between members and non-members of the traffic club is not primarily attributable to membership in the club. The two cases show that by analysing causal chains, one may uncover confounding factors that were not adequately controlled in a study. Lack of control for confounding factors remains the most serious threat to the validity of road safety evaluation studies.

Effects of potassium carbonate as an alternative road de‐icer to sodium chloride on soil chemical properties

SummaryThe effect of potassium carbonate on soil chemical characteristics was compared with that of the most common de‐icer, sodium chloride, in a 4‐yr outdoor pot experiment with poplar and lime trees. Soil pH was raised more by K2CO3 than by NaCl. Potassium carbonate increased the electrical conductivity mainly in the upper soil layers. When K2CO3 was applied at an average annual dose of 154 g m−2, only the water‐soluble fractions of calcium and magnesium were affected. At an average annual dose of 617 g m−2, total potassium increased by 33% and calcium was displaced from the exchange sites. Calcium saturation was reduced from 85% of the cation exchange capacity in the untreated control to 69% in the higher dose K2CO3 treatment and to 75% in the NaCl treatment. The results show that the negative impact of K2CO3 on soil chemical and osmotic properties is as high as that of NaCl. For plants, however, potassium carbonate in contrast to chloride is not toxic and, applied in moderate doses, may even remedy potassium deficiencies in roadside trees.

The Impact of Road De-Icing Salts (NaCl) on Colloid Dispersion and Base Cation Pools in Roadside Soils

The maintenance of safe-driving conditions in snow and ice-affected areas in the wintertime includes the use of sodium chloride (NaCl) as de-icing salts. In this study, the impact of NaCl on soil-colloid mobilisation and exchangeable base-cation leaching has been evaluated. The chemistry of groundwater samples below an infiltration trench for highway runoff and leachate from column studies suggested that soil-colloid mobilisation had occurred, as the exchangeable sodium (Na) concentration and the electrical conductivity (EC) in the groundwater/column leachate reached the threshold values for colloid dispersion. Generally, samples with no dispersion problems had high Na and calcium (Ca) concentrations, suggesting that the initial effect of the de-icing salt was to stabilise the colloids. In the column study there was a good agreement between the degree of colloid dipersion problems and lead (Pb) concentration when the pH value was above 7.0. Significant negative correlations between Na/CEC (cation exchange capacity) and Ca/CEC in roadside soils from three sites indicated that Na preferentially displaces Ca from the exchange sites. However, the groundwater data indicated that Na ions also displace potassium (K) and magnesium (Mg). A positive effect of NaCl seen at one site was an increase in the K concentration, which is highly likely an effect of Na ions displacing fixed K between the layers of 2:1 type clay minerals. In soils lacking these types of clay minerals, severe K shortage may result from a high plant demand combined with the low K concentration in the readily available fractions in the original soil and a high susceptibility to leaching. The most significant impact on soil exchange processes was found to occur within 6 m from the road.

Investigation of the Conditions for the Production of Calcium Magnesium Acetate (CMA) Road Deicer in an Extractive Crystallization Process

Calcium magnesium acetate (CMA) is considered as the best road deicer to replace the environmentally unacceptable NaCl and CaCl2. However, the high cost of CMA prohibits its widespread use. The present study is dealing with the investigation of a crystallization method for the production of deicing CMA crystals of desired physical properties and the elucidation of the conditions under which such a product can be formed. Extractive crystallization is promising for the low cost production of CMA crystals considering that acetic acid is produced by a biochemical method and removed from the fermentation broth in situ by organic extractant systems. In this method, this organic phase, which contains the acetate ions is contacted with an aqueous phase which is the source of calcium and magnesium ions. The extractive crystallization process resulted in the production of well-formed, large, and non-spherical crystals of calcium acetate (CA), magnesium acetate (MA), and calcium magnesium acetate double salt (CMADS). The crystal size was affected by the concentration of acetic acid in both the organic and aqueous phases, whereas the crystal type and hydration level were determined primarily by the acetic acid concentration in the aqueous phase. The molar ratio of the precursor salts (CaCO3/MgCO3) in the reaction mixture was found to be the major factor for determining the habit and Ca/Mg content of crystals. Crystallization of CMADS was favored at high concentrations of acetic acid in the aqueous phase and at higher temperatures as shown from supplementary evaporation-to-dryness experiments.

Characteristics of road deicers produced from the utilization of water plant residuals and cement wastes

Abstract This paper examines the use of water plant sludge and cement wastes in the production of the CMA deicer. Experiments were conducted in a temperature controlled test chamber, to determine melting rates and ice penetration characteristics of these deicers at two sub‐zero temperatures. The freezer section of the refrigerator was modified and equipped with a temperature control mechanism to meet this objective. Ice melting was examined in terms of brine generated per gram of de‐icer powder. Penetration depths were read off directly from the vertical ice columns of the test apparatus. Results indicate a high potential for the use of these wastes as low‐cost raw materials for the production of the deicer.

Field Test Comparison of Calcium Magnesium Acetate to Salt

This paper focuses on the technical and operational aspects of calcium magnesium acetate (CMA) compared to those for salt for winter road deicing. The results are based on a winter road test conducted by the University of Nevada, Reno (UNR), for the Nevada Department of Transportation (NDOT), in the Lake Tahoe basin, during the winter of 1989–90. CMA test sections and salt control sections were employed to make comparative evaluations. Road conditions were monitored during winter storms in test and control sections. Reports from maintenance personnel and road monitors were used to evaluate resulting responses of test and control sections to determine the performance of the applied chemicals. Operational characteristics of CMA use were noted by NDOT supervisors. Topics addressed include the minimum temperature of CMA and salt effectiveness, the nature of CMA and salt interaction with varying road conditions, clearing times and levels of service for CMA and salt, and operational characteristics of CMA use. The results are correlated with other field studies.

Urban snow dump quality and pollutant reduction in snowmelt by sedimentation

Four snow dump sites in the Ottawa-Carleton region were analyzed for BOD, total and fecal coliforms, chlorides, sulfates, specific conductance, suspended solids, metals, and other parameters. Sites were sampled at various depths during the months of February through May. There was no trend in variation of quality in the dump piles with time. The black crust that formed on the top of the pile was heavily laden with solids and metals.Snowmelt samples were also taken over the same time period and analyzed for the above parameters. The process of snowmelt reduced the concentrations of most metals and suspended solids from the dump by 50–70%. Dissolved constituents in snowmelt are discharged at very high levels during the initial stages of snowmelt and rapidly decrease to low concentrations. Suspended solids and associated metals in snowmelt exhibited variability with snowmelt conditions and the state of the dump pile. The concentrations of a number of metals in settled snowmelt exceeded provincial objectives for surface waters.An analysis of settled snow dump and snowmelt samples for suspended solids and metals was conducted for settling periods of 1, 6, 12, and 24 h. A settling time from 2 to 6 h would achieve most of the removal that could be expected from sedimentation. The overall removal of suspended solids and the metals in settled snowmelt would generally be better than 90%. There were no significant trends in removal behavior as the snowmelt season progressed. The removal of metals lagged slightly behind the removal of suspended solids after settling because of the stronger association of metals with smaller sediment particles. The residue at the dump site is highly contaminated. Key words: snowmelt, runoff, stormwater, sedimentation, road deicing, snow dump, pollution.

Cells on Rotating Fibers for Wastewater Treatment

Fibers have a high surface area so many cells can be immobilized and when the fibers are rotated, fast reactions occur. When Celite® is entrapped in the fibers, even more area is provided. Half a pound of Celite® has the area of a football field! Toxic metals can be removed from wastewater. Pulp mill effluent can be cleaned. Phenol is degraded and the sulfur taken out of coal. A non-polluting road deicer is produced which doesn't corrode bridges or cars and ethanol for cars puts less lead into the air and water. When an RBC (rotating biological contactor) is run half full and a light shone in the top, the light hits a thin moving film to degrade dioxin.

Biomass derived alkaline carboxylate road deicers

Alkaline carboxylate road deicers such as calcium magnesium acetate are beginning to replace conventional chloride-containing deicers since they are less damaging to concrete, metal surfaces and living systems. The purpose of this project was to develop economical methods for the recovery of these superior road deicers from aqueous biomass pyrolysis liquors. Calcium formate/acetate/propionate deicers were successfully prepared in high yield from aqueous pyrolysis liquors derived from wood. These deicers are expected to be superior to calcium magnesium acetate deicers due to their high formate content. Deicer recovery should become commercially viable if the recovery of high-value industrial chemicals such as hydroxyacetaldehyde or glyoxal can be integrated with deicer recovery. Although technically straightforward, deicer production without by-product chemical recovery is uneconomical. Total pyrolysis liquor, derived from cellulose-rich biomass waste is a good source of deicer and other chemicals.

Calcium magnesium acetate (CMA) production from whey permeate: process and economic analysis

About 28 billion lbs of liquid whey produced from cheese manufacture are being wasted in the US. An anaerobic fermentation process is developed to produce calcium magnesium acetate (CMA) from whey permeate. CMA can be used to replace salt as a noncorrosive road deicer. A co-culture consisting of homolactic and homoacetic bacteria was used to convert whey lactose to lactate and then to acetate in continuous, immobilized cell bioreactors. The acetate yield from lactose was ∼ 95% ( w/ w), and the final concentration of acetic acid obtained from this homofermentative process was 4%. The acetic acid produced from fermentation can be readily recovered by solvent extraction with a tertiary amine and reacted with dolomitic lime (CA/MgO) to form a concentrated (>25%) CMA solution. This CMA solution can then be dried to form the granular CMA deicer. About 40 tons CMA can be produced from a plant processing 1.5 million lbs whey permeate per day, at a cost of $215/ton. The total capital investment is estimated at ∼ 7 million dollars, with a return rate of less than 1.5 years at the current market price of $600/ton.

A novel fermentation process for calcium magnesium acetate (CMA) production from cheese whey

A novel, anaerobic fermentation process is developed to produce calcium magnesium acetate (CMA) from cheese whey. CMA can be used as a noncorrosive road deicer. It poses no environmental threats and has many advantages over road salt. A coculture consisting of homolactic and homoacetic bacteria was used to convert whey lactose to lactate and then to acetate in a continuous, immobilized cell bioreactor. The acetate yield from lactose was ~95% (wt/wt) in this homofermentative process. The acetic acid produced from fermentation was recovered in a concentrated CMA solution by using an energyefficient extraction process. The development of a novel, extractive fermentation process to reduce product inhibition and to further increase reactor productivity is also discussed.

The removal of nitric acid to atmospheric particles during a wintertime field study

A field was conducted in Warren, MI, during the 1987/88 winter period to examined the reaction of HNO 3 with particulate salt from road deicing. Samples of gases and particles were collected on a daily basis over a 4-month period. If HNO 3 reacts with particulate salt, particles of sodium nitrate will be formed and gaseous hydrochloric acid will be released. Thus, during the periods of high salt concentrations, one would expect increases in HCl and particulate NO 3 − and a decrease in HNO 3. The effect was observed, although the total amount of NaNO 3 formed was not large. The increase in particulate NO 3 − did not appear in the large particle mode. Although more than 40% of the salt was present as very large particles (> 8 μm), most of the surface area was associated with small particles. Since the reaction occurred at the particle surface, the NO 3 − appeared in the small particle mode. Large-particle nitrate has been observed in association with sea salt and crustal particles and has also been attributed to reactions with HNO 3. These cases will be reconsidered based on the road salt results.

Effects of Calcium Magnesium Acetate Deicer on Small Ponds in Interior Alaska

ABSTRACT Whole-lake experiments were conducted on three ponds in interior Alaska to test the effects of calcium magnesium acetate (CMA), an experimental road deicer, on aquatic organisms. The CMA added to the test ponds equalled approximately one chemical application applied to 0.4 km of a typical section of road (one lane) draining entirely to a small pond. Calcium elevation did not persist into the next summer; it may have been flushed out by snowmelt. Acetate from the CMA mixture was apparently rapidly taken up by aquatic organisms and cycled for several months, depleting dissolved oxygen in the water. Dissolved oxygen became extremely low in a small pond of about 2,600 m3 treated with 55 mg/L calcium acetate (calculated from calcium elevation). Bacteria and algae both appeared to be stimulated by CMA additions, as indicated by higher standing crops in treated ponds. The algae were probably stimulated by bacterial metabolism products of the acetate, or by phosphorus in the CMA used. Cladocerans were mo...

Chemistry of Deicing Roads: Penetrating Ice

Experimental measurements of the rates at which sodium chloride, calcium chloride, urea, and calcium magnesium acetate (CMA) penetrate ice are consistent with a theory developed to predict this rate. These measurements and theory complement earlier studies of the rate at which ice can be debonded from road pavement. The mass transfer coefficients found from the penetration measurements are similar to those found from spinning ice disks, but are much less than those found for debonding. Possible reasons for this discrepancy and the steps that limit road deicing are discussed.

Impact of Calcium Magnesium Acetate Road Deicer on POTW Operation

Recently, calcium magnesium acetata (CMA) was identified by the Federal Highway Administration as a potentially suitable, noncorrosive road deicer substitute for sodium and calcium chloride. Research on the environmental effects of CMA has principally dealt with the effects of CMA on plant life and water quality in areas surrounding points of deicer application. However, in urban areas served by combined storm/sanitary sewer systems, most road deicing material is washed into the sewer system and, therefore, passes through the publicly owned treatment works (POTW). Because of the chemical nature of CMA, significant increases in organic loadings to POTW may result. The purpose of this technical note is to delineate potential adverse effects of CMA application on POTW operation, based on theoretical considerations and past collected runoff data for conventional deicing salts. The city of Buffalo, New York, is used as an example.

Contamination of Subsurface Waters by Road De-icing Chemicals

Abstract The application of road de-icing chemicals to urban and rural roads in southern Ontario represents a serious potential source of shallow subsurface contamination. These chemicals are highly soluble and are readily mobilized by surface water run-off. This run-off can subsequently enter the soil zone and migrate through the shallow subsurface resulting in degradation of groundwater quality in the underlying aquifer. Recent work has investigated the extent to which the inorganic constituents of road de-icing chemicals constitute a threat to groundwater in the shallow subsurface environment. This study has focused on a) determining the extent to which road de-icing chemicals are accumulating in the shallow subsurface; b) identifying diagnostic chemical parameters which will enable conclusive contaminant source identification; and c) assessing rates of road de-icing contaminant migration. Fifteen field sites were selected to sample sediments adjacent to urban and rural roads. A total of forty seven interstitial water samples were submitted for major ion (Na, K, Mg, Ca, Cl, SO4, HCO3, NO3), minor ion (F, I, Br), pH, electrical conductivity and trace constituent analyses. Preliminary results indicate that the shallow subsurface adjacent to the urban road sites contain considerably elevated Na, Cl, Ca, and Mg. Interstitial waters from urban road sites may contain from 103 to 104 mg/L Cl and 103 mg/L Na as compared to less than 102 mg/L Cl and less than 102 mg/L Na for interstitial waters sampled from rural road sites and park locations. The ratio I/Cl exhibits potential as a diagnostic indicator of source origin. Interstitial waters contaminated by road salt regularly show I/Cl ratios two orders of magnitude lower than I/Cl ratios for saline bedrock waters.

Geothermal energy: technological aspects of exploitation

Discusses the exploitation of geothermal energy once hot aquifers have been located. The drilling method is briefly described, and various steam cycles considered along with the choice of prime mover for the turbines. It is concluded that geothermal energy is best suited to the provision of base load in an integrated power system. District heating, hot water, and air conditioning applications are considered, e.g. in Reykjavik. Also considered are industrial applications such as the use of tepid water in fish farming, de-icing of roads, soil warming etc. Corrosion and pollution problems are examined and future prospects discussed

The Effect of Waste Water Reuse in Cold Regions on Land Treatment Systems

AbstractThe effect on ground water quality and soils and vegetation of treatment and disposal of municipal/industrial waste water on land in cold regions was investigated using six outdoor test cells. Winter application of waste water was feasible even at very cold air temperatures (<0.0°C) at the New Hampshire test site. High NO3‐N concentrations were observed in all treatments (5–15 cm/week) in both soils in early summer. This was explained as leaching of NH4‐N stored over the winter months after its oxidation to NO3 in early spring. Over the 12‐mo period of study, removal of organic C, BOD, suspended solids, fecal coliform bacteria, and phosphorus by the two soil types used (a Windsor sandy loam and a Charlton silt loam) was essentially complete. These had very little or no effect on ground water quality. The principal mechanism for nitrogen removal was found to be plant uptake, which was seasonally dependent. Application of 15− cm of secondary effluent per week to a sandy loam soil was not feasible because of the presence of > 10 mg/liter NO3‐N in the leachate for > 9 mo/year. Application of salts for road deicing during winter resulted in relatively higher concentrations of salts and Cl in the ground for a short period of time. No efforts were made to apply waste water according to plant need. Preapplication treatment is not necessary for the renovation of waste water by the soil‐plant systems. Movement of applied heavy metals to a depth of 15–30 cm in the high treatment soil was thought to be a result of a drop in soil pH resulting from this treatment. In all other treatments, heavy metals were confined to the top 15 cm of the soil.

Release of Mercury from Contaminated Freshwater Sediments by the Runoff of Road Deicing Salt

Release of Mercury from Contaminated Freshwater Sediments by the Runoff of Road Deicing Salt