Water Science and Technology, St. Lawrence Centre, Environment Canada, 105 McGill St., Montreal, QC H2Y 2E7, Canada.
Water Science and Technology, St. Lawrence Centre, Environment Canada, 105 McGill St., Montreal, QC H2Y 2E7, Canada.
Sci Total Environ. 2014 Feb 15;472:1036-43. doi: 10.1016/j.scitotenv.2013.11.116. Epub 2013 Dec 15.
Water deoxygenation is listed among the promising on-board treatment technologies to treat ships' ballast waters to reduce the risk of species transfer. We assessed the performance of a yeast-based bioreactive deoxygenation process in very cold water (<2°C) and determined the potential toxicity of the residual treated waters. Experiments using two treatment levels (0.5% and 1% v/v) were conducted in large-volume (4.5m(3)) tanks over 19 days at mean temperature of 1.5°C. Time to hypoxia varied between 10.3 and 16 days, being slightly higher than the predicted time of 9.8 days from previous empirical relationships. Water deoxygenation was achieved when yeast density exceeded 5×10(5) viable cellsmL(-1) and variation in time to hypoxia was mainly explained by difference in yeast growth. There was no oxycline and no significant difference in yeast density over the 2-m deep water column. Results from six bioassays indicated weak toxic response of treated waters at the 1.0% level, but no potential toxic response at the 0.5% treatment level. Results confirmed that the potential application of a yeast-based deoxygenation process for treating ships' ballast waters extended over the range of water temperature typically encountered during most shipping operational conditions. Time to reach full deoxygenation may however be limiting for universal application of this treatment which should be preferably used for ships making longer voyages in cold environments. There was no evidence that biological deoxygenation at low temperature did increase toxicity risk of treated waters to impede their disposal at the time of discharge.
水脱氧被列为有前途的船上处理技术之一，用于处理船舶压载水，以降低物种转移的风险。我们评估了基于酵母的生物反应脱氧过程在极冷水中（<2°C）的性能，并确定了残留处理水的潜在毒性。在平均温度为 1.5°C 的情况下，使用两个处理水平（0.5%和 1%v/v）在大容量（4.5m³）罐中进行了为期 19 天的实验。缺氧时间在 10.3 到 16 天之间变化，略高于以前经验关系预测的 9.8 天的时间。当酵母密度超过 5×10(5)个活细胞/mL 时，实现了水脱氧，缺氧时间的变化主要由酵母生长的差异解释。没有氧跃层，在 2 米深的水柱中酵母密度没有显著差异。六项生物测定的结果表明，处理水在 1.0%水平下的毒性反应较弱，但在 0.5%处理水平下没有潜在的毒性反应。结果证实，基于酵母的脱氧过程在处理船舶压载水方面的潜在应用可以扩展到船舶在大多数运输操作条件下遇到的水温范围内。然而，达到完全脱氧的时间可能限制了这种处理的普遍应用，这种处理最好用于在寒冷环境中进行长途航行的船舶。没有证据表明低温生物脱氧会增加处理水的毒性风险，从而阻碍在排放时对其进行处理。
