Chan-Won Lee

Removal of nitrogen and phosphate from wastewater by addition of bittern

Removal of nitrogen and phosphate through crystallization of struvite (MgNH(4)PO(4).6H(2)O) has gained increasing interest. Since wastewaters tend to be low in magnesium relative to ammonia and phosphates, addition of this mineral is usually required to effect the struvite crystallization process. The present study evaluated the feasibility of using bittern, a byproduct of salt manufacture, as a low-cost source of magnesium ions. High reaction rates were observed; the extent of nitrogen and phosphorus removals did not change beyond 10 min. Phosphorus removals from pure solutions with bittern added were equivalent to those obtained with MgCl(2) or seawater. Nitrogen removals with bittern were somewhat lower than with the alternate Mg(2+) sources, however. Application of bittern to biologically treated wastewater from a swine farm achieved high phosphate removal, but ammonia removals were limited by imbalance in the nitrogen:phosphorus ratio.

Ecological risk assessment of sediment in wastewater discharging area by means of metal speciation

Abstract This study was designed to evaluate the influence of wastewater discharge to the marine ecosystem after treatment plant construction. Heavy metal concentrations in sediment and bioavailability of the metals were analyzed and ecological risks were assessed using the results. Metal speciation for sediments collected in the wastewater discharging area was measured by a Shimadzu AA-680 atomic absorption spectrometer. The distribution of the metals among various geochemical phases was determined. Biological samples collected and analyzed were four species of crustacea, four species of bivalve, and seven species of fish. Exchangeable fraction of superficial sediment (0–2 cm layer) was Zn 35.09%, Ph 5.30%, Cu 0.86%, Cr 0.01% and Fe 0%. However, exchangeable fraction of deep layer sediment (15–20 cm) was not detected for all metals analyzed. Deeper sediments were found to have more residual fraction, and bioavailable phases decreased by depth, which provides an indication of the seriousness of wastewater discharge effect in this enclosed bay. The chemical concentrations observed to be associated with biological effects were sorted. The comparisons were made with regard to the potential for adverse biological effects. The potential of adverse biological effects in the sediments of wastewater discharge site was estimated as Zn 69.8%, Pb 35.8%, Cu 29.1%, and Cr 21.1%, respectively. Mullet ( Mugil cephalus ) among biological samples had the highest concentration of Zn in the muscle and liver organs. The bioconcentration factors (BCFs) of Zn by the mullet, mussel, oyster and crab were the highest among heavy metals determined. This result was well related to 81.6% of bioavailable phase Zn and 69.8% of adverse biological effects for the surface sediment.

Nitrite inhibition of aerobic growth of Acinetobacter sp.

Nitrite inhibition of Acinetobacter sp. growing under aerobic conditions was studied. Specific growth rates under non-limiting concentrations of acetate and dissolved oxygen averaged 0.62h(-1). Growth and phosphate uptake by Acinetobacter sp. were both inhibited by increasing nitrite concentrations. The median inhibitory concentration (IC50) of free nitrous acid (FNA) was 0.10 mg/L and the IC10 of FNA was 0.05 mg/L. Removing nitrite from cultures reversed the inhibitory effect. Comparison of the IC10 of FNA for Acinetobacter sp. to inhibitory concentrations for other wastewater heterotrophic bacteria suggests that Acinetobacter sp. are relatively sensitive to this compound.

Sedimentation pattern and sediments bioavailability in a wastewater discharging area by sequential metal analysis

Abstract Atomic absorption spectrometry was applied to investigate sedimentation pattern and sediments bioavailable phase (BAP) at 41 sites of a wastewater discharging area. The position of sampling sites was confirmed by the aid of a global positioning system (GPS). Contaminants discharged from a large wastewater plant are dispersed to the inner bay and the coastal line rather than the outer bay and the center waterway. The fractional composition of sediment Zn in the discharging area accounted for the presence of exchangeable 239 mg/kg (35.1%)>reducible 163 mg/kg (24.0%)>carbonate 149 mg/kg (22.0%)>residual 98 mg/kg (14.4%)>organic 31 mg/kg (4.6%) in sediment layers of 0–2 cm. However, the order was changed in layers of 15–20 cm as residual>reducible>organic>carbonate>exchangeable. The most abundant fraction of sediment Cu and Fe was organic Cu and residual Fe, respectively. The content of BAP in sediments are quite different with respect to metal species and sediment layer analyzed. It is obvious that sequential metal analysis is a useful tool in understanding dispersion of sediments and sedimentation patterns.

Improved water quality in response to pollution control measures at Masan Bay, Korea

The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005-2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ~1 month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.

CaO/CaCO₃ 다공체로 이루어진 활성 굴 패각의 물성 및 인 제거 효능에 관한 연구

In this study, the structure and properties of waste oyster shell and its phosphorus removal efficiency were investigated. Waste oyster shells are troublesome environmental waste in the coastal region where the oysters are produced. Waste oyster shells were pyrolyzed by bench-scale rotary kiln for its activation. It shows maximum 76% of phosphorus removal efficiency for the municipal wastewater and livestock wastewater. We found that the activated oyster shells can be used as a phosphorus removal agent with the consideration of high efficiency, easy processing, and cost effectiveness.

Dredging Index for Sediments Remediation Management

Dredging of contaminated sediments is one option often considered for remediation in coastal waters. There is a need to determine hot spots, areas of concern, and unpolluted areas in order to prioritize dredging operations. A dredging index was developed for this purpose by combining four different numerical sets of sediment quality guidelines into a quadrodiagram. The constructed quadrodiagram gives graphical information about sediment quality, whereas the dredging index provides a quantitative assessment of the degree of sediment quality degradation. Sediment quality data from a number of studied areas was compared in terms of the dredging index and was capable of distinguishing heavily impacted regions from lightly or nonimpacted regions.