Department of Civil Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
Environmental Science and Engineering Department, Environmental Research Laboratory, Indian Institute of Technology Bombay, Mumbai, Maharashtra, 400076, India.
Environ Sci Pollut Res Int. 2022 Sep;29(41):61954-61966. doi: 10.1007/s11356-022-19965-7. Epub 2022 Apr 5.
Heavy metals in higher concentrations are often encountered in domestic sewage of developing and under-developed countries. High metallic concentrations can stress reactor sludge biomass morphology impeding its performance in organics reduction. However, the extent of damage and ability of sludge biomass to recover from the metallic stress is not fully understood. Also, there is no protocol to identify and prevent the sludge biomass from metallic stress in fully functional sewage treatment plants (STPs). This study investigates performance, metabolic activity, morphology, and settling characteristics of the sludge biomass under different Co(II) stress conditions. The extent of recovery in biomass, when the supply of Co(II) metal ion was discontinued in the inlet stream, was explored. The study also proposed a protocol based on simple settling characteristics of sludge biomass to get an early indication of metal infiltration to prevent potential damage to the biomass morphology. Four sequencing batch reactors (SBRs) with Co(II) ion concentrations of 0 (designated as RCo0), 5 (RCo5), 25 (RCo25), and 75 mg/L (RCo75) in the feed were operated with a cycle time of 12 h. Reactors were operated for 35 days with Co(II) in the feed (termed as stressed phase operation) followed by 24 days of operation without Co(II) in the feed (termed as recovery phase operation). Results show that COD removal in reactor RCo75 reduced to 48% on the 10th day of stressed phase operation, showing a lag in COD removal due to metallic stress. The activity of biomass in reactors RCo5, RCo25, and RCo75 was reduced by 39%, 45%, and 49%, respectively, in the stressed phase compared to the biomass in control reactor. Recovery in COD removal efficiency and specific biomass activity were observed in all the reactors after the removal of metallic stress. The settleability of sludge biomass in reactors RCo25 and RCo75 was significantly affected. Transformation in the shape of flocs in reactor RCo25 and RCo75 biomasses revealed the prolonged effect of metallic stress, which was observed to be irreversible even during the recovery phase operation.
重金属在浓度较高的情况下通常存在于发展中国家和欠发达国家的生活污水中。高浓度的金属会对反应器污泥生物量形态造成压力，从而影响其有机物还原性能。然而，人们对污泥生物量所受的损害程度及其从金属压力中恢复的能力还不完全了解。此外，在功能齐全的污水处理厂（STP）中，也没有确定和防止污泥生物量受到金属压力的方案。本研究调查了不同 Co(II) 压力条件下污泥生物量的性能、代谢活性、形态和沉降特性。还探索了当入口流中断 Co(II) 金属离子供应时，生物量的恢复程度。该研究还提出了一种基于污泥生物量简单沉降特性的方案，以尽早发现金属渗透现象，防止生物量形态受到潜在损害。四个序批式反应器（SBR）的进水 Co(II) 浓度分别为 0（命名为 RCo0）、5（RCo5）、25（RCo25）和 75mg/L（RCo75），运行周期为 12 小时。反应器在进水含有 Co(II) 的情况下运行了 35 天（称为胁迫阶段运行），然后在没有 Co(II) 的情况下运行了 24 天（称为恢复阶段运行）。结果表明，在胁迫阶段运行的第 10 天，RCo75 中的 COD 去除率降至 48%，表明由于金属胁迫，COD 去除出现滞后。与对照反应器中的生物量相比，RCo5、RCo25 和 RCo75 中生物量的活性分别降低了 39%、45%和 49%。在去除金属胁迫后，所有反应器中的 COD 去除效率和特定生物量活性均有所恢复。RCo25 和 RCo75 中污泥生物量的沉降性能受到显著影响。RCo25 和 RCo75 中生物量絮体形状的变化表明金属胁迫的持续时间较长，即使在恢复阶段运行时，这种影响也是不可逆的。
