Hundreds of ready-mix concrete trucks are dispatched daily from ready-mix concrete plants. On average, a concrete truck has a carrying capacity ranging from 7 to 9 cubic metres of concrete, requiring about 1500 litres of water. In addition, 500 to 1300 litres of water are used to wash out the excess concrete when the truck returns. Based on these figures, it is clear that the ready-mixed concrete industry consumes large amounts of fresh water. The purpose of this study is to determine the feasibility of using the wash water as mixing water in new concrete. The specific goal of this project is to determine the influence of the high pH and dissolved solids content of the wash water on the durability of concrete, particularly with respect to de-icing salt induced corrosion of steel reinforcement. Two types of mix designs were used in this research: a standard class N and a higher strength, structural C2 concrete. Two sets of concretes specimens were made with both mix designs: one with wash water and one with clean water. The project consists of a multi-component experimental program, beginning with wash water characterization, then pore solution and cement chemistry, followed by an evaluation of the effect of wash water on concrete workability and mechanical properties, resistance to de-icing salt scaling, and corrosion of reinforcing steel embedded in the concrete. In addition, the effect of the wash water on the effectiveness of air entraining agents (AEA) is being determined using air void analysis of specimens with different AEA contents. On the basis of the results obtained from the comparative study using wash water versus tap water, it appears that wash water can be used as mixing water for the production of concrete without compromising the durability properties related to corrosion and salt scaling performance. In addition, the mechanical and plastic properties of wash water concrete meet all standards pertaining to the use of wash water concrete and are similar to those of tap water concrete. Finally, the pore solution, thermal analyses, and water analyses of wash water and tap water showed comparable results. Overall, with regards to the tests conducted thus far, the use of wash water as mixing water in concrete poses no durability concerns.

Hundreds of ready-mix concrete trucks are dispatched daily from ready-mix concrete plants. On average, a concrete truck has a carrying capacity ranging from 7 to 9 cubic metres of concrete, requiring about 1500 litres of water. In addition, 500 to 1300 litres of water are used to wash out the excess concrete when the truck returns. Based on these figures, it is clear that the ready-mixed concrete industry consumes large amounts of fresh water. The purpose of this study is to determine the feasibility of using the wash water as mixing water in new concrete. The specific goal of this project is to determine the influence of the high pH and dissolved solids content of the wash water on the durability of concrete, particularly with respect to de-icing salt induced corrosion of steel reinforcement. Two types of mix designs were used in this research: a standard class N and a higher strength, structural C2 concrete. Two sets of concretes specimens were made with both mix designs: one with wash water and one with clean water. The project consists of a multi-component experimental program, beginning with wash water characterization, then pore solution and cement chemistry, followed by an evaluation of the effect of wash water on concrete workability and mechanical properties, resistance to de-icing salt scaling, and corrosion of reinforcing steel embedded in the concrete. In addition, the effect of the wash water on the effectiveness of air entraining agents (AEA) is being determined using air void analysis of specimens with different AEA contents. On the basis of the results obtained from the comparative study using wash water versus tap water, it appears that wash water can be used as mixing water for the production of concrete without compromising the durability properties related to corrosion and salt scaling performance. In addition, the mechanical and plastic properties of wash water concrete meet all standards pertaining to the use of wash water concrete and are similar to those of tap water concrete. Finally, the pore solution, thermal analyses, and water analyses of wash water and tap water showed comparable results. Overall, with regards to the tests conducted thus far, the use of wash water as mixing water in concrete poses no durability concerns.

Column flotation cells have become increasingly popular in the coal industry due to their ability to improve flotation selectivity. The improvement can be largely attributed to the use of froth washing, which minimizes the nonselective entrainment of ultrafine minerals matter into the froth product. Unfortunately, the practice of adding wash water in conventional flotation machines has been largely unsuccessful in industrial trials. In order to better understand the causes of these failures, a detailed in-plant test program was undertaken to evaluate the use of froth washing at an operating coal preparation plant. The tests included detailed circuit audits (solid and liquid mass balances), salt tracer studies, and release analyses. The data collected from these tests have been used to develop criteria that describe when and how froth washing may be successfully applied in industrial flotation circuits. A second series of tests was developed to look at other alternatives to froth washing and their effectiveness. This involved two-staged flotation circuitry. A two-staged approach was developed because the existing flotation cells did not have enough residence time to support froth washing. The process owner wanted to evaluate possible alternatives to column cell flotation. The testing included release analysis testing as well as a detailed series of tests with percent solids control to the secondary flotation unit. / Master of Science

Tunnels have become increasingly important in the development of road networks to meet rising transportation demands. Washing of road tunnels must be performed regularly to ensure traffic safety. The washing procedure generates significant amount of polluted wash water. Before discharge to a receiving water body, treatment is necessary to avoid potential degradation of the water quality. In this study, 12 in situ sedimentation experiments were conducted to evaluate treatment efficiency of sedimentation, with and without the addition of chemical flocculent. The findings showed that untreated tunnel wash water was highly polluted with total suspended solids (804-9690 mg/l), PAHs (0.4–29 μg/l) and heavy metals. Most pollutants were associated with the particulate material. Significant correlations (r2 > 0.95) were found between suspended solids and metals. Efficient removal of pollutants was possible by sedimentation with addition of flocculent. Within 20 hours of sedimentation low concentrations were reached of suspended solids (<15mg/l), PAHs (<0.1 μg/l), Cd (<0.05 μg/l), Cr (< 8 μg/l), Hg (<0.02 μg/l), Pb (<0.5 μg/l) and Zn (< 60 μg/l). The results confirm the possibility to treat tunnel wash water with sedimentation and flocculation and to discharge treated wash water to a recipient, provided particular attention is given to very sensitive water bodies.

The purpose of this study is to evaluate the convenience and effectiveness of using a disc filter to treat washing water from the sand filters at Sundet wastewater treatment plant. The disc filter is used aiming for the reduction of suspended solids and phosphorus. The study was divided in two main experimental stages. During the first stage laboratory jar-tests were performed in order to identify which flocculation aid was more suitable, this was further on used to improve the water treatment. Based on the laboratory trials results, two different polymers (1 and 2) were chosen to be tested at pilot scale. The second stage involved the pilot filter operation itself; this period was as well divided in two sub-stages where filter cloths with two different pore openings were tested. During the first sub-stage the pilot operated with an 18 μm pore opening filters cloth and both polymers. At the end of the first half polymer 1 showed to be more efficient and so it was further used throughout the second sub-stage in combination with a 10μm pore opening filter cloth. As from theoretical knowledge the phosphorus and suspended solid removal were expected to be between 75% and 90%, results which were achieved during both laboratory trials and pilot filter. The best results were observed with the 10μm pore opening filter cloth and polymer 1. Also, additional results from pilot trials performed at Sundet after the study period are presented.

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The presence of postharvest sanitizers has shown to be an effective approach to reducing microbial cross contamination in agricultural washing operations. However, choosing an appropriate sanitizer can be challenging due to produce commodity, processing conditions and interference with organic load. Current research shows a wide variety of methods to mimic the organic load of vegetable processing conditions, with paddle mixing and blender as the most commonly used. Controlling and understanding the physiochemical properties of wash water is key in maintaining sanitizer efficacy. The effects of simulated wash water preparation method on the physiochemical properties were tested at 0 and 50 COD(mg/L) and no significant difference was observed. However, at high levels of organic load results showed a significant difference between turbidity values at 1,500 COD. Free residual chlorine titration methods were compared, using DPD-titrimetric and Iodometric method. Results showed a significant difference between titration methods in organic load heavy environments. Commercially available chlorine based sanitizers, Pure Bright™ Germicidal Bleach and Clorox® Germicidal Bleach, were compared to a concentrated solution of sodium hypochlorite. Pure Bright™ Germicidal Bleach showed to perform the best by reducing 7 log CFU/ml of E. coli O157:H7 after 30 seconds in no organic load environments, whereas Clorox Germicidal bleach was able to reduce 7 log CFU/ml of E. coli O157:H7 after 30 minutes. These studies aim to provide best management practices for small in medium growers in the implementation of antimicrobial solutions for the maintenance of water quality in postharvest washing solutions.