再生水补水的景观水体优势藻种水华爆发阈值条件的确定

Determination of the threshold conditions for the outbreak of dominant algal blooms in landscape water bodies supplemented with reclaimed water

再生水景观补水是污水再生利用的重要途径,但水华频发是其利用的主要制约因素。以从典型再生水补水的景观水体中识别出的3种优势藻种为研究对象,采用室内静态实验方法研究了在温度、光照强度和营养盐浓度共同作用下的优势藻种的生长状况。结果表明:在温度T=30℃、照度=9000 lx、N/P较低的再生水补水水体中,水华微囊藻更易成为优势藻种,仅培养3 d,藻密度就由1.0×10^(4)cell/mL增加到9.1×10^(4)cell/mL,接近水华爆发的阈值条件(大于10×104 cell/mL);普通小球藻和四尾栅藻较适合在T=25℃、光照强度分别为5000和7000 lx、N/P相对较高的再生水原水中生长,培养5 d可达到或接近水华爆发阈值条件。降低再生水体中的磷浓度可在一定程度上抑制藻类的生长,当再生水补水水体中TP浓度从0.3 mg/L降低到0.1 mg/L时,对普通小球藻和四尾栅藻的抑制率分别为56.6%和40.7%,但对水华微囊藻的抑制作用相对较弱。研究结果揭示了再生水景观补水水体中藻类的生长规律,为控制藻华爆发提供了一定的理论依据。

Landscape replenishment with reclaimed water is one of the most important ways of sewage recycling,but frequent occurrence of algal blooms is the main bottleneck limiting its utilization.Three preponderant algae species identified from the typical reclaimed water bodies of landscape replenishment were taken as the research objects,and their growth status under the combined effects of temperature,light intensity and concentration of N/P were studied through indoor static experiments.The results show that Microcystis is more likely to become the dominant algae species at T=30℃,light intensity=9,000 lx in low N/P reclaimed water.After only three days of cultivation,the agal density became 91×10^(3)cell/mL compared with 10×10^(3) cell/mL before cultivation,approaching the threshold condition for blooming(10×10^(4)cell/mL);Chlorella vulgaris and Scenedesmus quadricauda like to grow in the raw reclaimed water with T=25℃,light intensity divided into 5,000 lx 7,000 lx,and relatively high N/P.They reached the threshold of alga bloom within 5 days of cultivation.The reduction of the P concentration can restrain the growth of alga.When the TP decreased from 0.3 mg/L to 0.1 mg/L in the reclaimed water,the inhibitory rates of the two kinds of green alga were 56.6%and 40.7%,respectively;however,the reduction of phosphorus concentration had relatively weak inhibitory effect on Microcystis.The research results give a theoretical support for comprehending the expansion of alga and curbing the outbreak of algal blooms in the reclaimed water bodies of landscape replenishment.