Kyung-Sok Min

Removal of Ammonium from Tannery Wastewater by Electrochemical Treatment

Abstract The removal of ammonium from coagulated tannery wastewaters was investigated by an electrochemical method using Ti/IrO2 as an anode. Operating variables including the current density, pH and chloride concentration were considered in order to determine their effect on the ammonium removal efficiency. A maximum ammonium removal rate of 78.9% was achieved after 30 min of electrochemical treatment with 4 A dm−2 of current density. During the electrolysis, it had been observed that the ammonium removal was accompanied with an elimination of the organics. Generation of hydroxyl radical was identified during the experiment with hydroxyl radical probe compound of pCBA. Chloride ion worked as the scavenger of hydroxyl radical. Role of free chlorine was the main oxidant for the elimination of ammonium and organic substances. As a result, the biodegradability of tannery wastewater increased after electrochemical treatment. The energy consumed per 1 kg of ammonium removal was 26.6 kWh for initial NH4-N concentration of 870 mg L−1.

Acidogenic Fermentation: Utilization of Wasted Sludge as a Carbon Source in the Denitrification Process

Laboratory scale batch experiments were conducted at 20°C to investigate the acidogenic fermentation for the conversion of wasted sludge into short chain fatty acids (SCFA) to be utilized as a carbon source in the denitrification process. Hydraulic retention time (HRT), volatile solid (VS) loading rate and pH were studied as these are the important parameters governing the production of volatile fatty acids (VFA). Four different phases were investigated by varying these parameters. HRT was varied from 2.7 to 8.2 days whereas VS loading rate was varied from 1.2 to 3.6 g d−1. VFA production decreased with the increase in HRT above 2.7 days. 538.37±19.39 mg VFAproduced l−1. d−1 (0.176±0.010 mg VFAproduced mg−1 VSfeed) was found as the maximum value of VFA at 2.7 days. The present results based on wasted sludge showed that almost 0.0483±0.0016 mg VFA (as COD mg−1 initial COD) and about 5 % of soluble COD production were achieved, which are slightly less than the results reported for primary sludges. The rates of VFA production increased with the increase in VS, however, opposite results were obtained when pH was increased in the reactor. SCFA/FA ratios during fermentation were found in the range of 67-73 %. The specific denitrification rates (SDNR) of methanol (2.20±0.44mg NO3-N g−1 MLVSS · h−1) and the fermenter supernatant (2.00±0.45 mg NO3-N g−1 MLVSS · h−1) were found to be comparable. Fermenter supernatant, therefore, has the potential to be utilized as a carbon source. However, the results need to be investigated further on a larger scale to ascertain their validity.

Full Scale UASB Reactor Performance in the Brewery Industry

In this paper the 7 year experience of the Oriental Breweries, located in Kumi, Korea utilizing a full-scale upflow anaerobic sludge blanket (UASB) reactor for the anaerobic pretreatment of brewery wastewater is presented. The anaerobic pretreatment system selected has successfully achieved the desired treatment efficiency for the brewery wastewater during that period and it has also continued operation even with low wastewater concentrations (average CODcr 1,400 mg l−1) and lower flow rates than specified by the design parameters. The CODcr removal of the UASB reactor averaged over 80% throughout the entire period, incurring normal running expenses of only

Diffuse pollutant unit loads of various transportation landuses

0.20∼0.31 m−3 of treated water. In addition a further economical feature of the process was the utilization of the gas digester production as the municipal gas source, reducing total operating expenses around 30 to 45% and costing the plant only

Role of Foulant-Membrane Interactions in Organic Fouling of RO Membranes with Respect to Membrane Properties

0.1 m−3. Maintenance of good granule production, which is always a key issue in operating UASB systems, was not possible by this installation, however, so frequent expensive reseeding of the reactor was often necessary due to biomass washout. The full scale and lab scale research revealed that underloading can be as detrimental as overloading, due to excessively long retention time in the UASB system for the overall operating period and to excessive pre-acidification and/or incorrect reactor configuration of the completely mixed type. To enhance the sludge granulation, therefore, the installation of a pre-acidification reactor in the UASB system treating easily biodegradable substrates such as brewery wastewater is not necessary because adequate pre-acidification can occur in the equalization tank.

Effect of biologically mediated pH change on phosphorus removal in BNR system for piggery waste treatment

ABSTRACT A four-year monitoring study was conducted to determine the diffuse pollutant unit loads for the six representative transportation landuses (i.e., highway, parking lot, bridge, service area and toll gate) in urban areas in Korea. Pollutant event mean concentrations (EMCs) were calculated from 123 storm events at eleven sites and the average annual rainfall and runoff coefficients were determined to estimate the unit loads using the National Institute of Environmental Research (NIER) method. Apparent differences in the unit load values existed among landuses as explained by the high variability of EMCs for different rainfall events. The study has found that runoff from bridges and highways contained the highest loadings of TSS and COD while service areas are the primary sources of nutrients and metals. The results of this study could be used by the Ministry of Environment (MOE) to separate the unit loads of transportation landuses from the urban area category in the current unit load system. The v...

Enhancement of reactor performance and pelletization by reactor modification in UASB system

Initial fouling behavior due to membrane-foulant interactions was investigated by atomic force microscopy for various reverse osmosis membranes with different surface properties. Carboxylate modified latex and unmodified latex particles were used as surrogates of organic foulants. The results showed that the membrane-foulant adhesion forces were mainly governed by membrane surface properties such as hydrophobicity and surface charge. Stronger adhesion forces were determined for the membranes with more hydrophobic and less surface charge. Fouling experiments were further carried out to correlate the adhesion force data to actual flux-decline curves. A remarkable correlation was obtained where the membranes with stronger adhesion force more suffered from flux decline.

Performance evaluation and a sizing method for hydrodynamic separators treating urban stormwater runoff.

Since applicable amount of animal waste to farm land has been greatly reduced because of the nutrient overload, nitrogen and phosphorus removal from animal waste has received a great attention. This study was conducted to evaluate how phosphorus was removed during biological nutrient removal (BNR) from piggery waste using laboratory and full scale units operated at 25 to 40°C. The phosphorus removal was performed by chemical precipitation with struvite and hydroxyapatite (HAP), cellular formation, it is basically related with pH and organic and nitrogen loads resulting in influent COD/N ratios. The removal efficiencies increased from 50 to 90% as COD/N ratios increased to 6 to 7, but carbon was not limited beyond this ratio for denitrification resulting in a stable pH. Overall, about 70% of the phosphorus removal was due to the precipitates of struvite and/or HAP, and the remaining removal was due to the cellular P formation. Any significant temperature effect on phosphorus removal was not observed within the operating temperature. In order to maximize phosphorus removal in BNR system, additional anoxic stage must be furnished prior to discharge its final effluent after oxic stage.

Biological removal characteristics of phenol with filtration bio-reactor

Abstract Reactor performance and pelletization characteristics by reactor modification in a UASB system were investigated. The modified lab UASB reactor with a settler comprising 50% of the total reactor volume showed better performance in removing soluble organics, as well as producing lower TSS effluents at higher loading rates. The reason for the improved performance may be the formation of a deep sludge blanket in the modified settler. The advantages of the modified reactor system are observable in methane production and alkalinity requirements. Furthermore, the pellets from the UASB system with a modified settler showed better settleability and biomass holding capacity. The chemical composition of the biopellets was a little different from the common bacterial formula of C5H7O2N. Morphological characterization with SEM revealed many clusters, in terms of the physiological properties of hydrogen‐utilizing organisms, on the surface of pellets taken from the high hydrogen partial pressure zone in the modified reactor. This observation also suggests that the modified UASB system provides a better environment for the growth of hydrogen‐utilizing organisms.

Optimization of phosphorus reduction in BNR process for urban watershed management

This study reports on 6 years of performance monitoring of stormwater hydrodynamic separators in Korean urban catchments. One hundred and thirty-seven storm events were monitored in four hydrodynamic separators of two different types from 2006 to 2012. Mean values of the event average removal efficiencies of total suspended solids (TSS) for the four hydrodynamic separators were 43.69, 8.54, 42.84, and 14.35% with corresponding mean values of the event average surface overflow rates of 28.62, 40.07, 16.02, and 38.81 m/h, respectively. The low TSS removal efficiency was due to the high instantaneous surface overflow rates frequently occurring throughout a storm event and the abundance of fine particle fractions in the inflow (median particle diameter <75 μm). The Weibull function was used to simulate particle size distribution (PSD) in the runoff and the simulated PSD functions were further applied to the discrete settling theory to develop curves of TSS removal efficiency, as a function of surface overflow rate and median particle size of the inflow. The developed curves should be useful in determining the design peak flow rate and the size of a hydrodynamic separator for a stated goal of TSS removal efficiency.