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Non-Chemical Disinfection & Dechlorination to Protect RO and Demineralizer Treated Boiler Make-up Water
Chlorine and biocides have traditionally been used to mitigate biofouling and manage microbial induced corrosion, and are commonly injected into the feed
lines of the water treatment process at power plants to reduce the microbial load. However, when the water treatment process consists of reverse osmosis (RO)
trains, it is important to make sure the membranes are protected from oxidation by chlorine. Therefore, dechlorination is undertaken to remove free chlorine
compounds from the feedwater in order for the RO trains and other chlorine-sensitive equipment to operate properly.
In this paper, a technology is evaluated which uses broad-spectrum ultraviolet (UV) lamps for the reduction of chlorine and disinfection. Through
photodecomposition by UV light, the system decomposes the free chlorine oxidant. Additionally, the technology provides disinfection to reduce the
membrane biofouling potential.
The core of the discussed UV system is its water disinfection chamber made of high-quality quartz surrounded by an air block instead of traditional
stainless steel. This configuration uses fiber optic principles to trap the UV light photons and recycle their light energy. The photons repeatedly
bounce through the quartz surface back into the chamber, effectively lengthening their paths and their opportunities to inactivate microbes.
The efficacy of the technology, coupled with its specific operating principles and ease of use, allows for a unique non-chemical approach to dechlorinating
and disinfecting boiler make-up water.
PowerPlant Chemistry 2017, 19(5), 235–239
Removal of 125Sb from Radioactive Liquid Waste
This paper describes the synthesis, characterisation and application of a composite exchanger – hydrous zirconium oxide (HZO) coated on polyurethane
foam – for the removal of 125Sb from radioactive waste. In batch studies, removal of 80–100 % of Sb(V) was observed in the pH range
of 1–13. The presence of competing anionic species up to 1 000 mg · L–1 and dissolved solids up to
3 000 mg · L–1 had an insignificant impact on antimony removal. The exchange capacity of HZO was found to range
between 0.7–0.9 mEq · g–1. The role of surface hydroxyl groups in the removal of antimony could be established by
x-ray diffraction and Fourier-transform infrared spectroscopy studies. In column studies, complete removal of antimony was observed up to 1 200 bed volumes
of 1 mg · L–1 Sb(V) solution prepared in tap water. In trials with 125Sb-bearing waste samples,
an average decontamination factor of 4 was obtained despite very high dissolved solids concentrations of 30 g · L–1.
PowerPlant Chemistry 2017, 19(5), 245–252
Insights and Lessons Learnt from a Scaling Event in a Cooling Tower Part II: Results and Discussion on the Efficacies of
Scale Predictive Indices, Scale Inhibitor(s), and On-Line Cleaning Method(s)
This is the second half of a two-part article on a scaling incident that occurred at the Shand Power Station, SaskPower. The paper describes a simple scale
predictive index based on the ratios of conductivity to calcium and magnesium concentrations for the early detection of supersaturation and a high tendency
towards scale deposition on heat exchanger surfaces within recirculating cooling waters treated with scale inhibitors. With this predictive index, the
effectiveness of the scale inhibitor is evaluated based on the dosage concentrations vis-à-vis the water chemistry during the scaling incident.
Using empirical data, the dependability and limitations of currently reported Ca2+ and SO42– ionic product guidelines
in preventing calcium sulfate scale deposition are also assessed. A distinction is made between the operational adverse impacts of CaCO3 and
CaSO4 scale deposition and their remedies. Details of on-line acid cleans to restore the generation unit back to normal load are also described.
The paper concludes with remarks listing various lessons learnt from the scaling episode.
PowerPlant Chemistry 2017, 19(5), 261–277
Press Release – 2017 Annual Meeting, Kyoto, Japan
Continuing a series of conferences that began in 1929 in London, 102 scientists, engineers and accompanying persons from 13 countries attended the
annual meeting of the International Association for the Properties of Water and Steam (IAPWS). The Japanese National Committee of IAPWS hosted the meeting
between the 27th August and the 1st September 2017 at the Kyoto Research Park in Kyoto, Japan. The highlights of the IAPWS working group
sessions and other proceedings of the executive committee are summarized in this release.
PowerPlant Chemistry 2017, 19(5), 278–279