Feasibility of developing a passive sampler for sampling heavy metals in BMPs for stormwater runoff management

Evaluation of solids removal and optimisation of backwashing for an upflow stormwater filtration system utilising novel floating fibrous media

Although filtration devices are already widely used for stormwater runoff treatment, there are much to be improved to ensure the required performance. Additionally, the performance of a device should be verified before on-site installation. In this context, an upflow filtration system using novel high porosity floating fibrous media formed into spherical shape was proposed and evaluated for solid capture and backwashing. At filtration velocities of 20-40 m/h, the maximum head loss was about 2 cm even under a solid load of 30 kg/m², and suspended solid (SS) removal efficiency was >96% throughout 300 min. A considerable amount of SS was removed in the pretreatment chamber, so the load on the media was reduced. Several models were tried to describe the solid capture in the media. The coefficients of solid attachment/detachment showed good correlations with filtration velocity. Other parameters indicated a variation of solid capture and permeability, which is unique to the media in this study. The backwashing with air and water for 1-2 min each showed good head loss recovery under the SS load up to 550-600 kg/m², and the SS discharge was more efficient when the stagnant water was drained before water backwashing. The results in this study suggest the high potential of the combination of fibrous media and upflow filtration system for the efficient control of the nonpoint source pollutants in stormwater runoff.

Performance of butyl rubber-based macroporous sorbents as passive samplers

In this study, two macroporous butyl rubber (BR)-based sorbents prepared in benzene (H-BR) and in cyclohexane (L-BR) with different porosities were synthesized by cryogelation technique. Their performances as a passive sampler were studied and then compared with commercially available silicon rubber (polydimethylsiloxane, PDMS) passive sampler. For that aim, polycyclic aromatic hydrocarbon (PAH) absorption rates of the sorbents in the short-term and their accumulation capacities in the long-term periods were investigated. Four PAHs (naphthalene, phenanthrene, fluoranthene, and pyrene) with a different number of aromatic rings were utilized. The concentrations of the PAHs in solutions were quantified by fluorescence spectrophotometer. The results showed that the BR sampler prepared in benzene (H-BR) generally has the highest absorption rates for all PAHs. The rate constants k (h^-1) of the H-BR, L-BR, and PDMS samplers were found as 1.07, 0.55, and 0.55 for naphthalene; 0.73, 0.16, and 0.09 for phenanthrene; 0.24, 0.26, and 0.08 for fluoranthene; and 0.97, 0.38, and 0.17 for pyrene, respectively. The highest PAH absorption capacity was found for the BR sorbents prepared in benzene for all PAHs. Thus, benzene was selected as the organic solvent rather than cyclohexane for further studies in the preparation of butyl rubber-based samplers. The H-BR possessing the highest absorption rate and capacity underlines their usage as a capable passive sampler for both short- and long-term monitoring activities in the aquatic environments.

Methods for Sample Collection, Storage, and Analysis of Freshwater Phosphorus

Although phosphorus (P) is an essential nutrient for biological productivity, it can cause freshwater degradation when present at fairly low concentrations. Monitoring studies using continuous sampling is crucial for documenting P dynamics in freshwater ecosystems and to reduce the risk of eutrophication. Despite literature updates of developments of the analytical methods for measurement of P species in natural waters, there has been no comprehensive review addressing freshwater sample collection, sample preparation, and sample treatment to fractionate and characterize different forms of P. Therefore, this paper aims to elaborate the different techniques for freshwater sampling and to introduce alternative laboratory methods for sample preservation and P fractionation. The advantages and disadvantages of various sampling techniques, including the traditional manual and the recently developed automatic and passive methods, are presented to highlight the importance of collecting representative freshwater samples. Furthermore, we provide suggestions for sample pretreatment, including filtration, transportation, and storage steps to minimize microbial activity and to maximize the accuracy of measurement of various P fractions. Finally, the most common laboratory methods to measure dissolved and particulate as well as the organic and inorganic freshwater P fractions are efficiently provided. Using this guide, a comprehensive monitoring program of P dynamics in freshwater ecosystems can be developed and applied to improve water quality, particularly of P-rich freshwaters.