Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5, Canada.
J Environ Manage. 2018 Aug 15;220:227-232. doi: 10.1016/j.jenvman.2018.05.044. Epub 2018 May 26.
Although the improved dewaterability and digestibility of primary biosolids subjected to thermal hydrolysis has been studied for decades, there are a surprisingly small number of studies exploring the use of this thermal treatment for digested biosolids that are typically left to settle in large settling lagoons. This is likely because of the high capital and operating costs associated with thermal hydrolysis, coupled with the limited applications and value of the resulting products. However, due to the anticipated increases in the amount of generated biosolids combined with issues surrounding potential environmental release and the limited availability of land for additional lagoons, other biosolids management strategies are being explored. Here, we show that thermal hydrolysis at 280 °C for 1 h resulted in 78.2 ± 0.8% settling after 2 h. Furthermore, addition of phosphoric acid to lower the pH of the hydrolysate to pH 3 resulted in increased settling rates, but the final volume of unsettled material after 2 h was statistically similar to the thermally hydrolyzed material without pH adjustment (75.7 ± 2.3%). Remarkably, when the pH of the digested biosolids was adjusted to 3 prior to thermal hydrolysis, a settling rate of 87.3 ± 1.1% was observed after just 15 min. Significantly, the dewaterability of thermally hydrolyzed biosolids was measured in our experiments through natural settling, without the use of external mechanics. Taken together, the data presented in this paper demonstrate that high temperature thermal hydrolysis is a promising method for accelerating the settling rates of digested biosolids and may represent a viable alternative to building and maintaining biosolids lagoons.
尽管热解技术已被研究了几十年，能够提高原生物固体的脱水性能和可消化性，但将这种热处理应用于通常在大型沉降池沉淀的消化生物固体的研究却少之又少。这可能是由于热解技术的高资本和运营成本，再加上由此产生的产品的应用和价值有限。然而，由于预计产生的生物固体数量增加，以及潜在的环境释放问题和用于额外池塘的土地有限，其他生物固体管理策略正在被探索。在这里，我们表明在 280°C 下热解 1 小时后，在 2 小时后沉淀率达到 78.2±0.8%。此外，添加磷酸将水解液的 pH 值降低到 3 会导致沉淀速率增加，但在 2 小时后未沉淀物质的最终体积与未经 pH 调整的热解物质在统计学上相似（75.7±2.3%）。值得注意的是，当在热解之前将消化生物固体的 pH 值调节到 3 时，仅在 15 分钟后就观察到 87.3±1.1%的沉淀率。重要的是，在我们的实验中，通过自然沉淀测量了热解生物固体的脱水性能，而没有使用外部力学。总的来说，本文提供的数据表明，高温热解是一种很有前途的方法，可以提高消化生物固体的沉降速率，并且可能代表一种替代建造和维护生物固体池塘的可行方法。
