衣藻中试修复稀土氨氮废水

Pilot-scale bioremediation of rare earths wastewater by Chlamydomonas sp. YC

摘要:

硫酸铵介导的南方离子型稀土浸取开采产生了大量含高氨氮尾水，引发了严重的环境污染问题。本研究以从原始稀土氨氮尾水中分离到的衣藻(Chlamydomonas sp.) YC为出发藻株，选择50 L柱式光生物反应器(airlift photobioreactors,AL-PBRs)和5 m³开放式跑道池光生物反应器(open race-way photobioreactors,ORWPs)两种中试反应器，研究该藻户外处理稀土氨氮尾水(NH₄⁺-N，约2 000 mg/L)的生长情况和尾水处理性能；此外，检测采收的藻粉氨基酸、脂肪酸等生化组分，评估其营养价值。结果表明，与ORWPs相比，衣藻YC在AL-PBRs中处理稀土氨氮尾水具有更高的生物量(1.1 g/L)、NH₄⁺-N (24.9%)与总氮去除率(20.4%)和CO₂的固定速率[125.0 mg/(L·d)]。对于藻粉生化组分方面，AL-PBRs和ORWPs获得的衣藻YC蛋白含量分别为44.5%和49.4%，油脂含量分别为9.1%和14.3%。同时，与大豆蛋白(0.657)相比，两种藻粉的必需氨基酸指数(essential amino acid indexes,EAAI)更高(均为0.900)，这表明衣藻藻粉具有更好的营养价值。本研究的结果表明，衣藻YC中试柱式光生物反应器室外处理稀土氨氮尾水的工艺可能是一种潜在集成生物固碳、污水处理和藻粉开发的耦合技术。

关键词:稀土高氨氮尾水;衣藻YC;户外规模化处理;营养价值评估

Abstract:

The extraction of rare earth elements (REEs) through in-situ leaching with ammonium sulphate [(NH₄)₂SO₄] had resulted in the production of a large volume of ammonium-rich wastewater, causing severe environmental pollution. This study aimed to assess the ability of an indigenous microalga Chlamydomonas sp. YC, isolated from REEs wastewater, to directly treat real REEs wastewater under outdoor conditions in 50 L airlift photobioreactors (AL-PBRs) and 5.0 m³ open race-way photobioreactors (ORWPs). Additionally, the harvested Chlamydomonas sp. YC biomasses from these two pilot photobioreactors were comprehensively analyzed to evaluate the nutritional values. The results showed that Chlamydomonas sp. YC in AL-PBRs exhibited higher biomass production (1.1 g/L), greater removal efficiencies in NH₄⁺-N (24.9%) and total nitrogen (20.4%), as well as higher CO₂ fixation rate (125.0 mg/(L·d)), compared to those of ORWPs. Moreover, the Chlamydomonas sp. YC biomasses obtained from the two pilot photobioreactors contained 44.5% and 49.4% protein, 9.1% and 14.3% lipids. Moreover, Chlamydomonas sp. YC in the two pilot photobioreactors displayed essential amino acid indexes (EAAI) of 0.900, which was higher than that of soybean protein (0.657), indicating superior nutritional values. In conclusion, the implementation of the process involving Chlamydomonas sp. YC in AL-PBRs under outdoor conditions holds promise as a coupled microalgal biotechnology for the simultaneous removal of NH₄⁺-N from REEs wastewater, and the capture of CO₂ for the production of valuable biomass.

Key words:rare earths ammonium wastewater;Chlamydomonas sp. YC;outdoor pilot-scale;nutritional values evaluation