Biodegradable Organic Carbon Concentrations Research Articles

Characterization and source identification of organic matter in view of land uses and heavy rainfall in the Lake Shihwa, Korea

The characteristics and sources of organic matter in water of the Lake Shihwa, which receives inputs from rural, urban, and industrial areas, were evaluated by examining the biodegradable organic carbon concentration, fluorescence spectra, and carbon and nitrogen isotope ratios, especially during rainy season and dry season. The organic matter transported from rural areas was of refractory nature, while that of industrial origin decomposed rapidly. As compared to the dry season, the organic matter in the rainy season was characterized by a reduced labile fraction. During the dry season, the autochthonous organic matter dominated in the lake, however, the contributions of allochthonous organic sources by industrial and rural areas significantly increased at rainy season. This investigation revealed that the transport of organic matter of anthropogenic origin to the Lake Shihwa was mainly influenced by heavy rainfall. Moreover, each anthropogenic source could differently influence the occurrence of organic matter in water of the Lake Shihwa.

Interaction between phosphorus and biodegradable organic carbon on drinking water biofilm subject to chlorination

To examine whether phosphorus and biodegradable organic carbon interact to impact biofilm density and physiological function of biofilm-forming bacteria under conditions relevant to chlorinated drinking water distribution systems. The 2 x 2 factorial experiments with low and high levels of phosphorus and biodegradable organic carbon were performed on 4 -week-old drinking water biofilms in four separate pipe systems in the presence of chlorine. Experimental results revealed that biofilm heterotrophic plate count levels increased with the increase in biodegradable organic carbon concentration, showed no response to increases in levels of phosphorus and was not affected by interaction between phosphorus and biodegradable organic carbon. However, a significant positive interaction between phosphorus and biodegradable organic carbon was found to exist on biofilm mass and physiological function and/or metabolic potentials of biofilm communities; the effects of biodegradable organic carbon on biofilm mass and physiological function of biofilm-forming bacteria were accelerated in going from low to high level of phosphorus. Biodegradable organic carbon was found to be the primary nutrient in regulating biofilm formation in drinking water regardless of the presence of chlorine. It can be therefore concluded that the removal of an easily biodegradable organic carbon is necessary to minimize the biofilm growth potential induced by the intrusion of phosphorus. Phosphorus introduced to drinking water may interact with biodegradable organic carbon, thus leading to measurable impact on the biofilm formation.

Effects of Primary Substrate Concentration on NDMA Transport during Simulated Aquifer Recharge

N-nitrosodimethylamine (NDMA) is known to be highly carcinogenic and is present in drinking water, wastewater, and a variety of foods. Because of its presence in chloraminated water at nanogram per liter concentrations, NDMA has become an emerging issue for reclaimed water which may be used for aquifer recharge or irrigation. This research investigated the fate of NDMA in two soil column systems used to simulate subsurface transport. One column system was operated under aerobic conditions with increasing primary substrate concentration where the biodegradable organic carbon (BDOC) in reclaimed water was used as the primary substrate. The reclaimed water content in the influent was increased from 0 to 25% in the column to increase the BDOC concentration. Negligible NDMA removal was observed at 0% reclaimed water and increasing the primary substrate in the influent resulted in NDMA removal suggesting that biodegradation of NDMA might be a cometabolic process. The effects of redox conditions on NDMA fate was studied by operating a second column system with 100% reclaimed water under anoxic conditions and then changing the conditions to aerobic. It was observed that NDMA removal was similar under both aerobic and anoxic condition, however, much lower effluent concentrations were observed under aerobic conditions. Under anoxic condition, a normalized mass removal rate of 254 ng NDMA/mg DOC was observed which increased to 273-ng NDMA/mg DOC under aerobic conditions. The majority of NDMA and substrate removal occurred in the first of three columns in series column under both aerobic and anoxic conditions. Normalized mass removal rates of NDMA after the first, second, and third columns were 372, 30, and 20 ng NDMA/mg DOC, respectively. Since the majority of dissolved organic carbon was also removed in the first column, NDMA biodegradation was consistent with cometabolic activity. Batch tests verified the biodegradation removal potential of NDMA. Addition of a methylotrophic substrate, methanol and an aromatic substrate, toluene, did not increase NDMA removal.

The role of organic matter in the removal of emerging trace organic chemicals during managed aquifer recharge

This study explored the effect of different bulk organic carbon matrices on the fate of trace organic chemicals (TOrC) during managed aquifer recharge (MAR). Infiltration through porous media was simulated in biologically active column experiments under aerobic and anoxic recharge conditions. Wastewater effluent derived organic carbon types, differing in hydrophobicity and biodegradability (i. e., hydrophobic acids, hydrophilic carbon, organic colloids), were used as feed substrates in the column experiments. These carbon substrates while fed at the same concentration differed in their ability to support soil biomass growth during porous media infiltration. Removal of degradable TOrC (with the exception of diclofenac and propyphenazone) was equal or better under aerobic versus anoxic porous media infiltration conditions. During the initial phase of infiltration, the presence of biodegradable organic carbon (BDOC) enhanced the decay of degradable TOrC by promoting soil biomass growth, suggesting that BDOC served as a co-substrate in a co-metabolic transformation of these contaminants. However, unexpected high removal efficiencies were observed for all degradable TOrC in the presence of low BDOC concentrations under well adopted oligotrophic conditions. It is hypothesized that removal under these conditions is caused by a specialized microbial community growing on refractory carbon substrates such as hydrophobic acids. Findings of this study reveal that the concentration and character of bulk organic carbon present in effluents affect the degradation efficiency for TOrC during recharge operation. Specifically aerobic, oligotrophic microbiological soil environments present favorable conditions for the transformation of TOrC, including rather recalcitrant compounds such as chlorinated flame retardants.

Biodegradable dissolved organic carbon concentration of feed water and NF membrane biofouling: a pilot train study

This pilot train study compares the biofouling potential of two river waters that had been subjected to different pretreatment schemes conducting to equivalent microbial cells contents but different total and biodegradable organic carbon concentrations. Permeability and pressure drop of nanofiltration (NF) membranes were continuously monitored during the experiments. After a twenty week period of filtration, the membrane modules were autopsied, the composition and organization of membrane foulants were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and confocal laser scanning microscopy (CLSM). The ATR-FTIR spectra and CLSM observations of the fouled membranes revealed the presence of a biofilm at the membranes surface for the two feed waters. A positive correlation was observed between the biodegradable organic carbon concentration (BDOC) of feed water and the biofouling extent at the membrane surface: the BDOC concentration of feed water increase induced higher biofilm development. A longitudinal pressure drop increase was observed only with the water containing the higher concentration of BDOC whereas permeability decreases were equivalent with both feed waters. In conclusion, BDOC control through efficient pretreatments of raw water is a critical point for prevention of biofouling and maintenance of performances of NF membranes used in river water treatment.

Factors affecting denitrification rates in experimental wetlands: Field and laboratory studies

To identify the conditions that promote high rates of denitrification we systematically investigated the interactions of wetland age, water temperature, organic carbon, macrophytic type and density, hydraulic conditions on denitrification rates in field and laboratory experiments. In the field, nitrate removal was consistently greater in a shallow, young, well-mixed constructed wetland, regardless of temperature and despite lower sediment denitrification potential (DNP), than in mature, more diverse, less well-mixed wetlands. We believe the presence of a benthic mesh, which supported a dense periphytic biofilm, to be partly responsible for the unexpectedly high observed rates. We measured the DNP of wetland sediments and periphyton in the laboratory with the acetylene block method under different temperatures, nitrate concentrations, and carbon sources. The overall DNP of periphyton was greater than the corresponding sediment samples on a per cell basis. We hypothesize that the organic carbon produced by the periphytic algae is readily degradable and promoted the higher denitrification rates. We found a positive relationship between DNP and biodegradable organic carbon concentration and identified chemical markers illustrating that biodegradability is promoted by a combination of polyhydroxyaromatic and polysaccharide parent structures. These findings highlight the importance of organic quality and the role of periphyton in accelerating the rates of denitrification in wetlands.

Microbial Responses after Disinfectant Change to Ozone in a Full-Scale Distribution System

Ozone is a promising alternative disinfectant when the concentration of organic carbon is high in the source water. The microbial responses to primary disinfectant change from monochloramine to ozone in a full-scale distribution system were investigated. Several water quality parameters including heterotrophic bacteria and a new parameter, growth potential (GP), were determined from the finished water and at three different distribution system locations before and after switching to ozone for a period of 12 months. The GP assesses the potential of the water to sustain growth of bacteria. The literature suggests that ozonation will result in a higher biodegradable organic carbon concentration and will therefore stimulate bacterial growth. Biodegradable organic carbon concentration (BDOC) and HPC increased but GP decreased after ozonation during the study period. In order to exclude seasonal effects, the data from the same seasons of the previous year were compared in the statistical analyses. Our findings showed that among the water quality parameters, HPC, disinfectant dose and total organic carbon (TOC) concentration showed statistically significant differences between the two years (paired t-test, p<0.05). When ozone was used as primary disinfectant the TOC was 1.5 times higher than when chloarmine was used, but the HPC and disinfectant dose were lower. Thus the switch of the primary disinfectant to ozone did not increase bacterial growth. At the lower dose, the disinfectant dose was effective enough to control bacterial regrowth in the distribution system during the study period.