Advanced Water Management Centre, Gehrmann Building, Research Road, The University of Queensland, St. Lucia, Queensland 4072, Australia.
Water Res. 2015 Sep 15;81:84-91. doi: 10.1016/j.watres.2015.05.044. Epub 2015 May 23.
The acid production from the oxidation of hydrogen sulfide (H2S) in sewer air results in serious corrosion of exposed concrete surfaces in sewers. Large fluctuations of gaseous H2S concentrations occur in sewers due to the diurnal profiles of sewage flow and retention times and the necessity of intermittent pumping of sewage from pressure pipes into gravity pipes. How the high concentrations of H2S due to these events may affect H2S uptake and subsequent corrosion by concrete sewers is largely unknown. This study determined the effect of short- and long-term increases in H2S levels on the sulfide uptake rate (SUR) of concrete surfaces with an active corrosion layer. The results showed that during the high load situation the SUR increased significantly but then decreased (compared to the baseline SUR) by about 7-14% and 41-50% immediately after short- and long-term H2S high-load periods, respectively. For both exposure conditions, the SUR gradually (over several hours) recovered to approximately 90% of the baseline SUR. Further tests suggest multiple factors may contribute to the observed decrease of SUR directly after the high H2S load. This includes the temporary storage of elemental sulfur in the corrosion layer and inhibition of sulfide oxidizing bacteria (SOB) due to high H2S level and temporary acid surge. Additionally, the delay of the corrosion layer to fully recover the SUR after the high H2S load suggests that there is a longer-term inhibitive effect of the high H2S levels on the activity of the SOB in the corrosion layer. Due to the observed activity reductions, concrete exposed to occasional short-term high H2S load periods had an overall lower H2S uptake compared to concrete exposed to constant H2S levels at the same average concentration. To accurately predict H2S uptake by sewer concrete and hence the likely maximum corrosion rates, a correction factor should be adopted for the H2S fluctuations when average H2S levels are used in the prediction.
下水道空气中的硫化氢（H2S）氧化产生的酸会导致下水道中暴露的混凝土表面严重腐蚀。由于污水流量和停留时间的日变化以及将污水从压力管间歇性泵入重力管的需要，下水道中的气态 H2S 浓度会发生大幅波动。由于这些事件导致的高浓度 H2S 如何影响混凝土下水道的 H2S 吸收和随后的腐蚀在很大程度上是未知的。本研究确定了短期和长期 H2S 水平升高对具有活性腐蚀层的混凝土表面的硫化物吸收率（SUR）的影响。结果表明，在高负荷情况下，SUR 显著增加，但随后（与基线 SUR 相比）分别在短期和长期 H2S 高负荷期后立即降低了约 7-14%和 41-50%。对于两种暴露条件，SUR 逐渐（在数小时内）恢复到基线 SUR 的约 90%。进一步的测试表明，多个因素可能导致在高 H2S 负荷后直接观察到 SUR 下降。这包括由于高 H2S 水平和暂时的酸冲击，元素硫在腐蚀层中的临时储存以及对硫化物氧化菌（SOB）的抑制。此外，由于高 H2S 负荷后腐蚀层完全恢复 SUR 的延迟表明，高 H2S 水平对腐蚀层中 SOB 的活性存在长期抑制作用。由于观察到的活性降低，与暴露于相同平均浓度的恒定 H2S 水平的混凝土相比，偶尔暴露于短期高 H2S 负荷期的混凝土的 H2S 吸收总体上较低。为了准确预测下水道混凝土中的 H2S 吸收量，因此在预测中使用平均 H2S 水平时，应采用 H2S 波动的校正因子。
