Research On The Removal And Passive Monitoring Of PAHs From Stormwater Runoff

At present,urban stormwater runoff has become the second major source of water pollution after industrial wastewater and domestic sewage,and is considered to be one of the main factors for the continuous deterioration of urban water quality.As one of the important components of organic pollutants in urban rainwater runoff,PAHs are global organic pollutants with carcinogenic,teratogenic and mutagenic characteristics.Some studies have used bioretention ponds to control PAHs and other trace organic pollutants in runoff.However,compared with conventional pollution indicators in runoff,there are still few studies on PAHs pollution control technologies in rainwater runoff in China.Therefore,how to use economic and effective monitoring technology is an important scientific problem urgently needed to be solved by Rain Water pollution Control Institute.In this study,a bioretention pond with three substrates of grass-soil,sand-soil,sand-carbon matrix was first constructed to evaluate the removal efficiency of the bioretention pond for PAHs in runoff by comprehensively considering the reduction ability of the retention pond on runoff.Secondly,evaluated the feasibility of passive monitoring of PAHs by polyurethane foam（PUF）passive samplers in stormwater runoff and optimal rain water management measures（BMPs）.Its main conclusions are as follows:（1）The removal rates of naphthalene,phenanthrene,anthracene and fluoranthrene were over 60%under 4 kinds of rainfall intensity,and decreased with the increase of rainfall intensity.Under the same concentration,the three fillers have certain selectivity for the purification of PAHs.The removal rate from high to low is:sand-carbon system>grass-soil system>sand-soil system,and with the increase of PAHs concentration,the removal rate also increases.The removal rate of PAHs from the three substrates was divided into two stages with time.The initial stage of contact was the rapid adsorption dominated by distribution,which could complete more than 65%of the total removal in a few minutes to a few hours.The removal rate of fecal coliform bacteria was 95%～65.3%,the removal rate of NH₄⁺-N was higher than 80%,the removal efficiency of NO₃^--N was not high,the removal efficiency of TN was generally lower than 35%,and the average removal rate was more than 92%.Considering the ability to control runoff pollutants and discharge runoff,sand-carbon matrix biological retention system is more suitable for urban applications prone to waterlogging.（2）t=0～30 min,PUF achieved rapid adsorption of PAHs,the adsorption rate of the four PAHs was above 85.76%,the CNTs was 35.82%～62.86%,the adsorption rate was much smaller than that of the PUF to the PAHs;The maximum adsorption capacity of PUF for naphthalene,phenanthrene,anthracene and fluoranthrene was:2681,3876,4016μg/g and5000μg/g,CNTs followed by 1541,1642,1681μg/g and 1712μg/g.PUF,by contrast,can quickly adsorb PAHs even if the contact time with rain is short,the accumulation of PAHs is linearly related to time,and the high adsorption capacity enables PUF passive samplers to monitor rain events for months or years.Under the influence of p H、salinity and soluble organic matter,the PUF passive sampler has good sampling stability.（3）During BMPs laboratory tests,using PUF passive sampling to sample the incoming and outgoing water of BMPs loaded with synthetic rainwater.At three different rainfall intensities,the sampling rate obtained from column BMPs was k₀into formula（5.4）to obtain the time-weighted average concentration of four PAHs similar to the actual concentration,with a ratio of 0.8～1.2;There was no significant difference PUF the removal efficiency of the PAHs in the BMPs predicted by the passive sampler compared with the actual treatment efficiency obtained by the control BMPs（p>0.05）.The results show that PUF passive sampler is feasible to monitor stormwater runoff and PAHs in BMPs.