Performance of a full-scale biofilm system retrofitted with an upflow multilayer bioreactor as a preanoxic reactor for advanced wastewater treatment

To enhance nitrogen removal in an existing microbial contact oxidation (MCO) system with a treatment capacity of 900 m3/d, an upflow multilayer bioreactor (UMBR) was chosen as a preanoxic reactor for the removal of organic matter and nitrate. The removal performance of the retrofitted plant was evaluated during the startup phase at a low temperature in winter. The high removal (>80%) of organic matter and suspended solids in the UMBR provided stable nitrification conditions in the MCO system, as a result of the substantial reduction in organic matter and solids loaded onto the MCO system. This treatment system showed a stable nitrogen removal efficiency of 75.3%, even in the low temperature range 7 to 10 degrees C. Phosphorus was completely removed by chemical precipitation. Production rates of excess sludge, as a function of the loads of influent flowrate and biological oxygen demand (BOD), were 0.022 kg dry solid/m3 wastewater and 0.132 kg dry solid/kg BOD.     

Implication of hydraulic properties of bioremediated diesel-contaminated soil

The hydraulic properties, such as hydraulic conductivity and water retention, of aged diesel-contaminated and bioremediated soils were examined and implications of the hydraulic properties for assessing bioremediation performance of soils were proposed. Bioremediation of diesel-contaminated soil was performed over 80 d using three treatments; (I) no nutrient added, column-packed soil, (II) nutrient added, column-packed soil, and (III) nutrient added, loosen soil. Diesel reduction in treatment I soil (control soil) was negligible while treatment III showed the greatest extent of diesel biodegradation. All treatments showed greatest rates of diesel biodegradation during the first 20 d, followed by a much retarded biodegradation rate in the remaining incubation period. Reduction of the degradation rate due to entrained diesel within inaccessible soil pores was hypothesized and tested by measuring the hydraulic properties of two column-packed soils (treatments I and II). The hydraulic conductivity of treatment II soil (nutrient added) was consistently above that of treatment I soil (no nutrient added) at pressure heads between 0 and 15 cm. In addition, the water retention of treatment II soil was greater at pressure heads <100 cm (equivalent to pore size of >30 microm), suggesting that biodegradative removal of hydrocarbons results in enhanced wettability of larger soil pores. However, water retention was not significantly different for control and biodegraded soils at pressure heads >100 cm, where smaller size soil pores were responsible for the water retention, indicating that diesel remained in smaller soil pores (e.g., <30 microm). Both incubation kinetics and hydraulic measurements suggest that hydrocarbons located in small pores with limited microbe accessibility may be recalcitrant to bioremediation.     

Optimum moisture levels for biodegradation of mortality composting envelope materials

Moisture affects the physical and biological properties of compost and other solid-state fermentation matrices. Aerobic microbial systems experience different respiration rates (oxygen uptake and CO2 evolution) as a function of moisture content and material type. In this study the microbial respiration rates of 12 mortality composting envelope materials were measured by a pressure sensor method at six different moisture levels. A wide range of respiration (1.6-94.2mg O2/g VS-day) rates were observed for different materials, with alfalfa hay, silage, oat straw, and turkey litter having the highest values. These four envelope materials may be particularly suitable for improving internal temperature and pathogen destruction rates for disease-related mortality composting. Optimum moisture content was determined based on measurements across a range that spans the maximum respiration rate. The optimum moisture content of each material was observed near water holding capacity, which ranged from near 60% to over 80% on a wet basis for all materials except a highly stabilized soil compost blend (optimum around 25% w.b.). The implications of the results for moisture management and process control strategies during mortality composting are discussed.     

Distribution of inorganic arsenic species in mine tailings of abandoned mines from Korea

The main objective of the present study is to determine arsenic species in mine tailings by applying an ion exchange method. Three abandoned mines, Jingok, Cheonbo and Sino mines in Korea, which had produced mainly gold, were selected for the collection and analysis of the tailings. It was found that the arsenic speciation using an ion exchange method was effective to separate As(III) and As(V) in leachate of mine tailings. The concentration of As(V) was found to be 63-99% in the leachate, indicating that As(V) would be the major arsenic species in the mine tailings and the tailings were under oxic conditions. The total concentrations of arsenic and metal elements in the mine tailings were up to 62,350 mg/kg As, 40 wt.% Fe, 21,400 mg/kg Mn, and 7,850 mg/kg Al. Sulfate was the dominant anion throughout the leachate, reaching a maximum dissolved concentration of 734 mg/l. The results of XRD and SEM in the mine tailings showed that main arsenic-containing minerals were pyrite (FeS2) and arsenopyrite (FeAsS) which would be the source of arsenic contamination in the study area.     

Long-term fate of the herbicide cinosulfuron in lysimeters planted with rice over four consecutive years

In order to elucidate the long-term fate of the sulfonylurea herbicide cinosulfuron, the 14C-labelled chemical was applied to a clay loam soil, encased in two lysimeters, 22 days after rice (Oryza sativa L.) transplanting, and rice plants were grown for four consecutive years. Throughout the experimental period, leaching through soil profiles, absorption and translocation by rice plants, and distribution of 14C by downward movement in the soil layers were clarified. The total volume of leachates collected through the lysimeter soil over the four years amounted to 168 and 146 L in lysimeters I and II, respectively. The leachates contained 2.43% and 2.99% of the originally applied 14C-radioactivity, corresponding to an average concentration of 0.29 and 0.41 microg/L as the cinosulfuron equivalent in lysimeters I and II, respectively. The total 14C-radioactivity translocated to rice plants in the third and fourth year was 0.69% and 0.60% (lysimeter I), and 1.02% and 0.84% (lysimeter II) of the 14C applied, respectively. Larger amounts of cinosulfuron equivalents (0.54-0.75%) remained in the straw in the fourth year than in any other parts. The 14C-radioactivities distributed down to a depth of 70 cm after four years were 56.71-57.52% of the 14C applied, indicating the continuous downward movement and degradation of cinosulfuron in soil. The non-extractable residues were more than 88% of the soil radioactivity and some 45-48% of them was incorporated into the humin fraction. The 14C-radioactivity partitioned into the aqueous phase was nearly 30% of the extractable 14C, suggesting strongly that cinosulfuron was degraded into some polar products during the experimental period. It was found out in a supplemental investigation that flooding and constant higher temperature enhanced mineralization of [14C]cinosulfuron to 14CO2 in soil, indicating the possibility of chemical hydrolysis and microbial degradation of the compound in the flooded lysimeter soil.     

Biodegradation and detoxification of organophosphate insecticide, malathion by Fusarium oxysporum f. sp. pisi cutinase

Efficiencies of two lypolytic enzymes (fungal cutinase and yeast esterase) in malathion degradation were investigated. Surprisingly, degradation rate of malathion by fungal cutinase was very high, i.e. almost 60% of initial malathion (500 mg l(-1)) was decomposed within 0.5 h, and nearly 50% of the degraded malathion disappeared within initial 15 min. With the yeast esterase, despite the same concentration, more than 65% of malathion remained even after 2-day treatment. During enzymatic degradation of malathion, two malathion-derived compounds were detected, and time-course changes in composition were also monitored. In the degradation by both fungal cutinase and yeast esterase, two additional organic chemicals were produced from malathion: malathion monoacid (MMA) and malathion diacid (MDA) by ester hydrolysis. Final chemical composition after 2 d was significantly dependent on the enzyme used. Fungal cutinase produced MDA as a major degradation compound. However in the malathion degradation by yeast esterase, an isomer of MMA was produced in abundance in addition to MDA. Toxic effects of malathion and its final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including MMA) by esterase severely caused membrane damage and inhibition of protein synthesis in bacterial cells, while in the fungal cutinase processes, malathion was significantly degraded to non-toxic MDA after the extended period (2 days).     

Factors influencing concentrations of dissolved gaseous mercury (DGM) and total mercury (TM) in an artificial reservoir

The effects of various factors including turbidity, pH, DOC, temperature, and solar radiation on the concentrations of total mercury (TM) and dissolved gaseous mercury (DGM) were investigated in an artificial reservoir in Korea. Episodic total mercury accumulation events occurred during the rainy season as turbidity increased, indicating that the TM concentration was not controlled by direct atmospheric deposition. The DGM concentration in surface water ranged from 3.6 to 160 pg/L, having a maximum in summer and minimum in winter. While in most previous studies DGM was controlled primarily by a photo-reduction process, DGM concentrations tracked the amount of solar radiation only in winter when the water temperature was fairly low in this study. During the other seasons microbial transformation seemed to play an important role in reducing Hg(II) to Hg(0). DGM increased as dissolved organic carbon (DOC) concentration increased (p-value < 0.01) while it increased with a decrease of pH (p-value < 0.01).     

Kinetics of the reduction of hexavalent chromium with the brown seaweed Ecklonia biomass

The dead biomass of the brown seaweed, Ecklonia sp., is capable of reducing toxic Cr(VI) into less toxic or nontoxic Cr(III). However, little is known about the mechanism of Cr(VI) reduction by the biomass. The objective of this work was to develop a kinetic model for Cr(VI) biosorption, for supporting our mechanism. The reduction rate of Cr(VI) increased with increasing total chromate concentration, [Cr(VI)], and equivalent concentration of organic compounds, [OCs], and decreasing solution pH. It was found that the reduction rate of Cr(VI) was proportional to [Cr(VI)] and [OCs], suggesting the simple kinetic equation -d[Cr(VI)]/dt=k[Cr(VI)][OCs]. When considering the consumption of organic compounds due to the oxidation by Cr(VI), an average rate coefficient of 9.33 (+/-0.65)microM(-1)h(-1) was determined, at pH 2. Although the function of the pH could not be expressed in a mechanistic manner, an empirical model able to describe the pH dependence was obtained. It is expected that the developed rate equation could likely be used for design and performance predictions of biosorption processes for treating chromate wastewaters.     

Comparisons of polybrominated diphenyl ethers levels in paired South Korean cord blood, maternal blood, and breast milk samples

Polybrominated diphenyl ethers (PBDEs), commonly used flame retardants, have been reported as potential endocrine disruptor and neurodevelopmental toxicants, thus giving rise to the public health concern. The goal of this study was to investigate the relationship between umbilical cord blood, maternal blood, and breast milk concentrations of PBDEs in South Korean. We assessed PBDE levels in paired samples of umbilical cord blood, maternal blood, and breast milk. The levels of seven PBDE congeners were measured in 21 paired samples collected from the Cheil Woman’s Hospital (Seoul, Korea) in 2008. We also measured thyroid hormones levels in maternal and cord blood to assess the association between PBDEs exposure and thyroid hormone levels. However, there was no correlation between serum thyroxin (T4) and total PBDEs concentrations. The total PBDEs concentrations in the umbilical cord blood, maternal blood, and breast milk were 10.7 ± 5.1 ng g⁻¹ lipid, 7.7 ± 4.2 ng g⁻¹ lipid, and 3.0 ± 1.8 ng g⁻¹ lipid, respectively. The ranges of total PBDE concentrations observed were 2.28-30.94 ng g⁻¹ lipid in umbilical cord blood, 1.8-17.66 ng g⁻¹ lipid in maternal blood, and 1.08-8.66 ng g⁻¹ lipid in breast milk. BDE-47 (45-73% of total PBDEs) was observed to be present dominantly in all samples, followed by BDE-153. A strong correlation was found for major BDE-congeners between breast milk and cord blood or maternal blood and cord blood samples. The measurement of PBDEs concentrations in maternal blood or breast milk may help to determine the concentration of PBDEs in infant.     

Laboratory determination of compost physical parameters for modeling of airflow characteristics

Physical parameters of 12 co-compost cover materials were experimentally determined and predicted variations in airflow characteristics were evaluated under varying moisture contents. Predicted air-filled porosity showed high correlation with measured air-filled porosity, facilitating development of a reliable model of air-filled porosity that makes it possible to predict the effect of varying moisture content and compost bed height on air-filled porosity and permeability. Predicted air-filled porosity decreased with increasing moisture content and compost depth for all materials. Air-filled porosity of corn stalks, oat straw, soybean straw, leaves, alfalfa hay, wheat straw, silage, wood shavings and sawdust was in the range of 38-99%. Turkey litter, soil compost blend and beef manure showed air-filled porosity values less than 30% near saturation and the bottom of pile. In concert with the findings of other researchers, effective particle size of all materials increased with increasing moisture content from 20% to 80% of water holding capacity (WHC). It increased dramatically near saturation. In general, permeability increased with increasing air-filled porosity and decreasing bulk density, but the relationship between permeability and moisture content is complex. Permeability is dependent on the balance between particle size and air-filled porosity. If the influence of aggregated particle size on the permeability is significant, it will compensate for the effect of reduced air-filled porosity caused by compaction and moisture content. In this case, permeability will increase; in the reverse case, it will decrease. Permeability decreased for corn stalks, oat straw, silage, wood shavings, soybean straw, sawdust, turkey litter and wheat straw with increasing moisture content from 20% WHC to 50% WHC, regardless of the depth of the compost bed. But the permeability increased with increasing moisture level from 50% to 80% WHC at moderate to shallow simulated bed depths. The soil compost blend and leaves showed the permeability increasing when the moisture increased not only from 50% to 80% WHC but also from 20% to 50% WHC. Permeability of alfalfa hay and beef manure always decreased with increasing moisture levels and pile depth. In this study the maximum wet bulk density and mechanical strength decreased with increasing the moisture content. The method described for determining physical properties under varying moisture contents and compost bed depths will be very useful for designing and modeling airflow characteristics of a mortality composting process with a variety of materials.