Marla C. Maniquiz-Redillas

Fractionation of heavy metals in runoff and discharge of a stormwater management system and its implications for treatment

A stormwater management system utilizing the mechanisms of sedimentation and filtration/infiltration was developed and constructed for the immobilization of suspended solids and heavy metal constituents (Fe, Zn, Pb, Cr, Cu, Cd, Ni) in runoff. Monitoring took place between May 2010 and November 2012 on a total of 24 storm events. This research on the fractionation of heavy metals in runoff and discharge of a stormwater system provided insight on the actual efficiency of the system and determined the implications for treatment of the particulate-bound and dissolved heavy metals in runoff. Results revealed that the partitioning of heavy metal load in runoff in either dissolved or particulate-bound were influenced by flow rate and total suspended solids load, and evident in high-intensity storm (rainfall-runoff event). On the other hand, the partitioning of heavy metal load discharge from the stormwater system was more apparent during the early period of discharge having higher variability in dissolved than particulate-bound heavy metal. Findings revealed that fractionation of heavy metals played an important role in the performance of the stormwater system; thus, must be considered in designing stormwater systems. For the stormwater system to be effective, it is recommended to design the system treating not only the early period of a storm (first flush criteria) rather until the peak part of the hydrograph (high flow rate where partitioning was greatest) from a load basis.

Evaluation of the capability of low-impact development practices for the removal of heavy metal from urban stormwater runoff.

ABSTRACT Low-impact development (LID) and green infrastructure (GI) have recently become well-known methods to capture, collect, retain, and remove pollutants in stormwater runoff. The research was conducted to assess the efficiency of LID/GI systems applied in removing the particulate and dissolved heavy metals (Zn, Pb, Cu, Ni, Cr, Cd, and Fe) from urban stormwater runoff. A total of 82 storm events were monitored over a four-year period (2010–2014) on six LID/GI systems including infiltration trenches, tree box filter, rain garden, and hybrid constructed wetlands employed for the management of road, parking lot, and roof runoff. It was observed that the heavy metal concentration increased proportionally with the total suspended solids concentration. Among the heavy metal constituents, Fe appeared to be highly particulate-bound and was the easiest to remove followed by Zn and Pb; while metals such as Cr, Ni, Cu, and Cd were mostly dissolved and more difficult to remove. The mass fraction ratios of metal constituents at the effluent were increased relative to the influent. All the systems performed well in the removal of particulate-bound metals and were more efficient for larger storms greater than 15 mm wherein more particulate-bound metals were generated compared to smaller storms less than 5 mm that produced more dissolved metals. The efficiency of the systems in removing the particulate-bound metals was restricted during high average/peak flows; that is, high-intensity storms events and when heavy metals have low concentration levels.

Treatment of suspended solids and heavy metals from urban stormwater runoff by a tree box filter

Particulates, inorganic and toxic constituents are the most common pollutants associated with urban stormwater runoff. Heavy metals such as chromium, nickel, copper, zinc, cadmium and lead are found to be in high concentration on paved roads or parking lots due to vehicle emissions. In order to control the rapid increase of pollutant loads in stormwater runoff, the Korean Ministry of Environment proposed the utilization of low impact developments. One of these was the application of tree box filters that act as a bioretention treatment system which executes filtration and sorption processes. In this study, a tree box filter located adjacent to an impervious parking lot was developed to treat suspended solids and heavy metal concentrations from urban stormwater runoff. In total, 11 storm events were monitored from July 2010 to August 2012. The results showed that the tree box filter was highly effective in removing particulates (up to 95%) and heavy metals (at least 70%) from the urban stormwater runoff. Furthermore, the tree box filter was capable of reducing the volume runoff by 40% at a hydraulic loading rate of 1 m/day and below.

Evaluation of a hybrid constructed wetland system for treating urban stormwater runoff

AbstractThis study developed hybrid constructed wetlands (CWs) for treatment of urban stormwater runoff pollutants. Hybrid CWs applied at narrow sections in urban areas are typically small and modular in type. Several treatment mechanisms were occurring in the hybrid system to treat high level of pollutant mass loading from urban stormwater runoff. A small scale hybrid CW comprised of a sedimentation tank, free water surface (FWS) CW, and horizontal sub-surface flow (HSSF) CW, was studied. A total of 10 test runs were simulated in the hybrid CW since July 2011–November 2012. Based on the results, almost 51–78% reduction in pollutants such as TSS, COD, TN, TP, and total heavy metals (Fe, Cu, and Zn) was achieved after passing the first and second units of the hybrid CW (i.e. sedimentation tank and FWS CW). Finally, additional 9–25% reduction of these pollutants was obtained as they went through the HSSF CW. Using normalized pollutant concentration with respect to the facility length, the appropriate size o...

Fate and removal of nutrients in bioretention systems

AbstractPhosphorus and nitrogen in different forms are the primary concern in surface water bodies nowadays since it causes eutrophication. A bioretention system, an example of green stormwater infrastructures reduces nutrients through biological processes such as plant uptake and microbial conversion of nitrogen known as bioremediation. In this study, the performance of two types of bioretention system in managing nutrients from urban stormwater runoff was investigated. Total phosphorus (TP) was reduced by 85% up to 86% in both bioretention types while total nitrogen (TN) was reduced by 49 and 55% in type A and type B bioretention, respectively. Among the plants species used in the study, Rhododendron indicum Linnaeus was identified as the most appropriate plant that should be used in bioretention systems considering factors such as number of flower per plants, plant decay rate, cost of plant, number of plant per reactor, and TN and TP uptake by plants. Based on the results, 25–32% of TN and 47–59% of th...

Determination of the number of storm events representing the pollutant mean concentration in urban runoff

Abstract Urban storm water quality monitoring is usually limited due to time and cost constraints, and thus, the determination of the minimum number of storm events that should be sampled necessary to estimate the pollutant mean concentration relative to the landuse is valuable. In this research, the minimum number of storm events was derived by considering both the variability of event mean concentration (EMC) values and the associated degree of uncertainty for a given set of measured storm events using monitored storm event data during a three-year period from 2009 to 2011 on five urban sites. Based on the findings, the required number of storm events could be determined using the propose method but representing only the 99 and 95% confidence limits of the site mean concentration (SMC) and differed depending on the pollutant. Results showed that a minimum of six to eight storm events were adequate to estimate the SMC of total suspended solids at low levels of uncertainties with relative standard error o...

Treatment of parking lot runoff by a tree box filter

ABSTRACT Nonpoint source pollutants were usually transported by stormwater runoff, especially in highly urbanized areas. For this reason, studies on stormwater management have been one of the major focuses of the Ministry of Environment of Korea at present. Application of tree box filter, an example of stormwater best management practice, is highly considered in Korea due to its minimal space requirements, applicability in landscaping and good pollutant-removal efficiency. This study investigated the efficiency of a tree box filter in reducing both the pollutant and volume of stormwater runoff generated from a parking lot. This study also identified the relationship between pollutant and volume reduction and the effects of varying amount of rainfall to the overall volume reduction efficiency of the system. The study proved the capability of the tree box filter in improving stormwater runoff quality that was more efficient in total suspended solids (TSS) and soluble heavy metals discharging only 9 and 30% ...

Optimization of the design of an urban runoff treatment system using stormwater management model (SWMM)

AbstractThis study presents an application of stormwater management model in predicting the optimal physical characteristics and rainfall design criteria of an established low impact development (LID) treating urban stormwater runoff. The optimization of this LID was performed for the purpose of enhancing the treatment performance and serve as future guidelines in designing treatment systems. The values of different calibration parameters used in the model were obtained from the 10 monitored storm events conducted from July 2010 to July 2013. Based on the findings, the runoff volume reduction of the system was found out to be directly proportional with storage volume/surface area (SV/SA) ratio. However, it was also dependent on the amount of rainfall during a storm event. For the total suspended solids load reduction of the system, it has no significant relationship with the rainfall but found to be directly proportional with SV/SA ratio as well. Lastly, the physical dimensions of the system were also ana...

Nitrogen mass balance in a constructed wetland treating piggery wastewater effluent

The nitrogen changes and the nitrogen mass balance in a free water surface flow constructed wetland (CW) using the four-year monitoring data from 2008 to 2012 were estimated. The CW was composed of six cells in series that include the first settling basin (Cell 1), aeration pond (Cell 2), deep marsh (Cell 3), shallow marsh (Cell 4), deep marsh (Cell 5) and final settling basin (Cell 6). Analysis revealed that the NH(+)4-N concentration decreased because of ammonification which was then followed by nitrification. The NO(-)2-N and NO(-)2-N were also further reduced by means of microbial activities and plant uptake during photosynthesis. The average nitrogen concentration at the influent was 37,819 kg/year and approximately 45% of that amount exited the CW in the effluent. The denitrification amounted to 34% of the net nitrogen input, whereas the accretion of sediment was only 7%. The biomass uptake of plants was able to retain only 1% of total nitrogen load. In order to improve the nutrient removal by plant uptake, plant coverage in four cells (i.e., Cells 1, 3, 4 and 5) could be increased.

Development of a stormwater treatment system using bottom ash as filter media

AbstractThis study investigated the applicability of bottom ash as filter media for a stormwater treatment facility. Filtration test experiments were conducted in a 30 × 15 × 15 cm transparent acrylic test reactor using a synthetic run-off, prepared from run-off collected from a wetted impervious road. The reactor designed as a stormwater treatment system and incorporated bottom ash as filter media was tested for three flow regimes (i.e. 200, 400, and 800 mL/min) to investigate the treatment performance of the system at various intensities during rainfall events. Based on the findings, the bottom ash media was able to reduce 70% of total suspended solids and more than 50% of iron, zinc, and lead from the synthetic run-off. A design guideline was developed which recommended a facility surface area to catchment area ratio of 0.007–0.015 for the effective treatment of 5, 7.5, and 10 mm design rainfall.