Total Organic Carbon Loading Research Articles

Sediment-bound total organic carbon and total organic nitrogen losses from conventional and strip tillage cropping systems

Global carbon (C) and nitrogen (N) cycles are closely linked to erosion and hydrologic processes. By reducing tillage erosion and runoff, sediment-bound C and N losses can be reduced. Published studies represent only a few soil types and regions and rarely directly compare tillage practices. The objective of this study was to quantify concentrations and sediment-bound total organic carbon (TOC) and nitrogen (TON) loads and enrichment ratios in runoff from 0.2-ha fields in rotational cotton (Gossypium hirsutum L.)-peanut (Arachis hypogea L.) production during a 7-yr study within a southeastern USA coastal plain landscape. The Ultisoils at the study site have loamy sand to sandy loam texture surface horizons. The fields were in either continuous conventional tillage (CT) or strip tillage (ST) and were at upper, middle, and lower landscape positions. Sediment-bound TON and TOC concentrations were significantly greater from ST than CT fields as were the TOC and TON enrichment ratios. However, due to greater surface runoff and sediment loss, TON and TOC loads were significantly greater from CT than ST fields. The CT and ST loads were significantly different at the upper and middle but not at the lower landscape position. Enrichment ratios, 14 to 19 for TON and 8 to 12 for TOC, were several-fold greater than reported in the limited available literature, where studies focused on finer textured surface soils. Our findings have highlighted the site-specific nature of erosion processes, how they affect sediment-bound C and N loss in agricultural landscapes, and how reducing tillage may impact sediment C and N dynamics. The observed enrichment ratios can be used to modify or adjust values used in current erosion models and improve their suitability for use in the region and elsewhere where surface soils have sandy texture and when practices like ST are implemented.

Water quality following extensive beetle-induced tree mortality: Interplay of aromatic carbon loading, disinfection byproducts, and hydrologic drivers

The recent bark beetle epidemic across western North America may impact water quality as a result of elevated organic carbon release and hydrologic shifts associated with extensive tree dieback. Analysis of quarterly municipal monitoring data from 2004 to 2014 with discretization of six water treatment facilities in the Rocky Mountains by extent of beetle impact revealed a significant increasing trend in total organic carbon (TOC) and total trihalomethane (TTHM) production within high (≳50% areal infestation) beetle-impacted watersheds while no or insignificant trends were found in watersheds with lower impact levels. Alarmingly, the TTHM concentration trend in the high impact sites exceeded regulatory maximum contaminant levels during the most recent two years of analysis (2013–14). To evaluate seasonal differences, explore the interplay of water quality and hydrologic processes, and eliminate variability associated with municipal reporting, these treatment facilities were targeted for more detailed surface water sampling and characterization. Surface water samples collected from high impact watersheds exhibited significantly higher TOC, aromatic signatures, and disinfection byproduct (DBP) formation potential than watersheds with lower infestation levels. Spectroscopic analyses of surface water samples indicated that these heightened DBP precursor levels are a function of both elevated TOC loading and increased aromatic character. This association was heightened during precipitation and runoff events in high impact sites, supporting the hypothesis that altered hydrologic flow paths resulting from tree mortality mobilize organic carbon and elevate DBP formation potential for several months after runoff ceases. The historical trends found here likely underestimate the full extent of TTHM shifts due to monitoring biases with the extended seasonal release of DBP precursors increasing the potential for human exposure. Collectively, our analysis suggests that while water quality impacts continue to rise nearly one decade after infestation, significant increases in TOC mobilization and DBP precursors are limited to watersheds that experience extensive tree mortality.

Predicting the export and concentrations of organic carbon, nitrogen and phosphorus in boreal lakes by catchment characteristics and land use: A practical approach.

The majority of C, N and P in boreal lakes are in organic form. Organically bound nutrients are released through biodegradation or photodegradation which affects the water quality, eutrophication and greenhouse gas emissions of lakes. We tested whether open land-use data combined with land-use-specific export coefficients can be used to predict total organic carbon (TOC), dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) loading and lake water concentrations. Using data from 12 lake catchments in eastern Finland, we found that land use and management of the catchment explained a substantial proportion of the variations in TOC (r 2=0.78), DON (r 2=0.55) and DOP (r 2=0.80) concentrations between lakes. The computation does not account for in-lake processes, which are reflected as mismatch between the predicted and observed concentrations. However, this simple practical approach is useful in ranking lakes according to their water quality. The results indicated that natural sources dominate TOC, DON and DOP exports; the background leachings accounted for 57-99%, 48-96% and 55-99% of TOC, DON and DOP export, respectively. The proposed method has promise as a practical decision support tool for assessing the impacts of land use on water quality. The results showed that possibilities to control TOC, DON and DOP loading to surface waters are limited to catchments where the peatland proportion is low and anthropogenic sources significant.

Control factors and scale analysis of annual river water, sediments and carbon transport in China.

Under the context of dramatic human disturbances on river system, the processes that control the transport of water, sediment, and carbon from river basins to coastal seas are not completely understood. Here we performed a quantitative synthesis for 121 sites across China to find control factors of annual river exports (Rc: runoff coefficient; TSSC: total suspended sediment concentration; TSSL: total suspended sediment loads; TOCL: total organic carbon loads) at different spatial scales. The results indicated that human activities such as dam construction and vegetation restoration might have a greater influence than climate on the transport of river sediment and carbon, although climate was a major driver of Rc. Multiple spatial scale analyses indicated that Rc increased from the small to medium scale by 20% and then decreased at the sizable scale by 20%. TSSC decreased from the small to sizeable scale but increase from the sizeable to large scales; however, TSSL significantly decreased from small (768 g·m−2·a−1) to medium spatial scale basins (258 g·m−2·a−1), and TOCL decreased from the medium to large scale. Our results will improve the understanding of water, sediment and carbon transport processes and contribute better water and land resources management strategies from different spatial scales.

Teleconnection of Instream Total Organic Carbon Loads with El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO)

<abstract> <b>Abstract.</b> Recently, total organic carbon (TOC) load has attracted a great deal of attention from water quality managers because it can form disinfection byproducts (DBP) during chlorination of drinking water. TOC loads in streams are generally affected by the hydrologic characteristics of a basin. In addition to the basin characteristics, hydrologic characteristics are affected by climate variability associated with a number of the oceanic and atmospheric phenomena that operate at seasonal to multidecadal time scales. Consideration of these large-scale climate phenomena, such as the El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO), are important for water quality managers because they can provide additional information for reducing TOC loads (and hence potential for DBP formation) in the drinking water supply. The objective of this study was to see if teleconnections exist between ENSO, NAO, PDO, and TOC loads. This study was conducted in the Big Creek watershed in southern Alabama in a series of steps. In the first step, model-simulated TOC loads were used to understand the effect of climate on TOC loads while keeping the land use and anthropogenic effects constant. In the second step, wavelet analysis, including cross wavelet analysis and wavelet coherence, was conducted to examine the correlation of ENSO, NAO, and PDO with TOC load in a time and frequency space. Analysis indicated that the common period of oscillations of various climate signals with TOC loads was detected even though NAO and PDO are decadal phenomena. Further, we examined the effects of ENSO, NAO, and PDO on large TOC loads using ten possible combinations of climate signals. TOC loads in El Niño winters and springs were significantly higher than in La Niña winters and springs, especially when ENSO was modulated with high (positive) NAO and high (positive) PDO. Similarly, TOC loads in El Niño or La Niña, occurring concurrently with high PDO and high NAO, were higher than TOC loads in neutral periods occurring concurrently with low (negative) PDO and low (negative) NAO. Interestingly, TOC loads in the La Niña phase were significantly higher than in the El Niño phase from August to October, especially when La Niña was modulated with high PDO and high NAO. Quantifying instream TOC loads with various climatic conditions is helpful for monitoring TOC loads and devising control measures.

Detection of the Sensitive Inflowing River Indicators Related to Non-Point Source Organic Pollution: A Case Study of Taihu Lake

Organic matter transport from watershed soil into an aquatic ecosystem plays a key role in the fate of contaminants and lake eutrophication. Special emphasis is needed to understand whether sensitive river indicators can reflect watershed non-point source organic carbon (OC) pollution, in which the accurate assessment of non-point source (NPS) pollution is crucial. This study selected a sub-basin within the Taihu basin, China, as the study site, a typical rural-urban fringe region undergoing rapid urbanization where soil organic carbon (SOC) loss would likely take place due to the integration of agriculture NPS and impervious surface NPS. The seasonal tendency of NPS soil organic carbon (SOC) loads were evaluated by using the integration of SEDD and PLOAD models, which consider the sediment adsorption fraction loads (Sed-OC) and runoff dissolved fraction loads (Dis-OC) together. And then the sensitive water indicators for OC loads were determined by measurements of inflowing river properties and stepwise regression analysis. The results showed that active dissolved carbon fraction loads were the dominant contributors to the total organic carbon loads (Tot-OC) and that Sed-OC loads have more spatial variation. With respect to sensitive river properties, the lignin owned the greatest correlation degree with different OC fraction loads, in which the correlation coefficient between particulate lignin and Sed-OC loads reached 0.782, which is the greatest among the different indicators. In addition, the colored dissolved organic matter (CDOM) was also correlated with Dis-OC loads. However, the particulate organic carbon (POC) was not well related to OC loads. The findings of this study are useful for better understanding the nutrient migration from watershed soil into aquatic ecosystem controlled by watershed NPS pollution.

Using recent high-frequency surveys to reconstitute 35 years of organic carbon variations in a eutrophic lowland river.

Concentrations of dissolved and particulate organic carbon (DOC and POC), total suspended solids (TSS), were measured daily, and phytoplankton pigments (chlorophyll-a and pheopigments) were measured every 3 days at three strategic stations along the eutrophic Loire River between November 2011 and November 2013 marked by a high annual and seasonal variability in hydrological regimes. This unique high-frequency dataset allowed to determine the POC origin (autochthonous or allochthonous). Some strong relationships were evidenced between POC, total pigments and TSS and were tested on a long-term database with a lower frequency (monthly data) to reconstitute unmeasured algal and detrital POC concentrations and estimate annual total organic carbon (TOC) fluxes from 1980 onwards. The results were subjected to only ≈25 % uncertainty and showed that the annual TOC fluxes at the outlet of the Loire River decreased from 520 10(3) tC year(-1) (i.e. 4.7 t km(-2) year(-1)) in the early 1990s to 150 10(3) tC year(-1) (i.e. 1.4 t km(-2) year(-1)) in 2012. Although DOC always dominates, the autochthonous POC represented 35 % of the TOC load at the basin outlet by the end of the 1980s and declined to finally represent 15 % only of the TOC. The control of phosphorus direct inputs and the invasion by Corbicula clams spp. which both occurred since the early 1990s probably highly reduced the development of phytoplankton. Consequently, the autochthonous POC contribution declined and TSS concentrations in summertime significantly decreased as well as a result of both less phytoplankton and less calcite precipitation. At the present time, at least 75 % of the POC has allochthonous origins in the upper Middle Loire but downstream, autochthonous POC dominates during summer phytoplanktonic blooms when total pigments concentrations reach up to 70 μg L(-1) (equivalent to 75 % of the total POC).

Production of biofuels from sweet sorghum juice via ethanol–methane two-stage fermentation

Sweet sorghum juice is rich in fermentable sugar. Combining ethanol fermentation with methane fermentation to convert sweet sorghum juice to biofuels not only maximizes the energy recovery, but also reduces the environmental load. A two-stage fermentation, consisting of continuous ethanol fermentation and thermophilic methane fermentation, was developed to convert sweet sorghum juice to productions of ethanol and methane. The results of batch ethanol fermentation indicated that it was essential to supplement the feedstock with nutrients in order to improve the ethanol yield. Continuous ethanol fermentation could be performed at 35°C without decreasing the ethanol yield at a dilution rate of 0.3h−1, and ethanol yield and productivity of 88.5% and 20.3g/L/h were obtained, respectively. In contrast, the productivity was improved to 27.4g/L/h by increasing the dilution rate to 0.4h−1 at a fermentation temperature of 33°C. The stillage eluted from the ethanol production process was subjected to thermophilic methane fermentation. After adjusting the C/N ratio of the stillage to 40, a total organic carbon (TOC) removal efficiency of 87.0% and gas evolution rate of 1200mL/g-TOC were achieved, even at a high TOC loading rate of 10g/L/d by adding (NH4)2SO4 of 0.1g/L-stillage.

Predicting Total Organic Carbon Load with El Niño Southern Oscillation Phase Using Hybrid and Fuzzy Logic Approaches

Abstract. During drinking water treatment, chlorine reacts with total organic carbon (TOC) to form disinfection byproducts (DBP), some of which can be carcinogenic. Additional treatment required to remove TOC before chlorination significantly increases treatment cost. There are two main sources of TOC in a water supply reservoir: (1) the watershed draining to the reservoir, and (2) the internal loading within the reservoir. Of these two sources, the watershed TOC load can be significant, especially when the watershed has large wetland areas. TOC loads in the Southeast U.S. can be affected by El NiA±o Southern Oscillation (ENSO)-induced climate variability. Since ENSO can be forecasted a few months in advance, ENSO-based TOC load forecasts can be used to tailor additional treatment required for TOC removal (e.g., activated carbon) before chlorination, thus reducing treatment costs. The objectives of this study were to quantity the effect of ENSO on watershed TOC loads and develop data-driven modeling approaches for forecasting TOC loads. Four hybrid and four fuzzy logic models, with different model architectures, were developed for forecasting watershed TOC loads using temperature, precipitation, NiA±o 3.4, and Trans NiA±o Index (TNI). This study concludes that the hybrid models are suitable for estimating real-time TOC loads, while the fuzzy logic models are suitable for qualitative forecasting of TOC loads with one-month lead time. In addition, this study highlights the importance of incorporating ENSO information into data-driven models in ENSO-affected regions.

Hydrothermal Carbonization of Biomass: Major Organic Components of the Aqueous Phase

AbstractProcess waters obtained from hydrothermal carbonization (HTC) of wheat straw, a biogas digestate derived thereof, and four woody biomass feedstocks were quantified regarding the total organic carbon (TOC) and selected organic compounds. HTC runs revealed that TOC loads were largely unaffected by process severity or type of feedstock whereas the C2–C6 fatty acids, determined by GC, displayed clear effects of temperature and feedstock. HPLC demonstrated simultaneously the initial increase and subsequent consumption of cellulose‐derived furfural and 5‐hydroxymethylfurfural as well as the increase of the lignin‐derived 2‐methoxyphenol. 2‐Methylbenzofuran, an example for a substance potentially harmful to aquatic biota, was observed in high concentration in the HTC liquor from wheat straw‐based feedstocks.

The Public Water Supply Protection Value of Forests: A Watershed-Scale Ecosystem Services Analysis Based upon Total Organic Carbon

We developed a cost-based methodology to assess the value of forested watersheds to improve water quality in public water supplies. The developed methodology is applicable to other source watersheds to determine ecosystem services for water quality. We assess the value of forest land for source water mitigation of total organic carbon (TOC) through the use of linked watershed and reservoir simulation models and cost-based valuation economics. Watershed modeling results indicated that expected urbanization will increase TOC loads to Converse Reservoir (Mobile, AL). Reservoir model results indicated that future median TOC concentrations increased by 1.1 mg·L−1 between 1992 and 2020 at the source water intake. Depending upon dynamic reservoir TOC concentrations, additional drinking water treatment with powdered activated carbon (PAC) often is necessary between May and October to comply with Safe Drinking Water Act regulations. The cost for additional treatment was calculated using minimum and maximum volume treated with simulated TOC concentrations at the source water intake. Daily simulated TOC concentrations for the base scenario using 1992 land cover (3% urban) were compared with simulated TOC concentrations following forest to urban land conversion predicted in the watershed by 2020 (22% urban). The daily cost for additional drinking water treatment with PAC was calculated if simulated TOC concentrations exceeded 2.7 mg·L −1 . The mean increase in daily treatment costs between base and future scenarios ranged from $91 to $95 per km 2 per day for forest land water purification ecosystem services.

Storage, properties and seasonal variations in fine‐grained bed sediment within the main channel and headwaters of the River Sanginjoki, Finland

AbstractLowland catchments in Finland are intensively managed, promoting erosion and sedimentation that negatively affects aquatic environments. This study quantified fine‐grained bed sediment in the main channel and upstream headwaters of the River Sanginjoki (399.93 km2) catchment, Northern Finland, using remobilization sediment sampling during the ice‐free period (May 2010–December 2011). Average bed sediment storage in river was 1332 g m−2. Storage and seasonal variations were greater in small headwater areas (total bed sediment storage mean 1527 g m−2, range 122–6700 g m−2 at individual sites; storage of organic sediment: mean 414 g m−2, range 27–3159 g m−2) than in the main channel (total bed sediment storage: mean 1137 g m−2, range 61–4945 g m−2); storage of organic sediment: mean 329 g m−2, range 13–1938 g m−2). Average reach‐specific bed sediment storage increased from downstream to upstream tributaries. In main channel reaches, mean specific storage was 8.73 t km−1, and mean specific storage of organic sediment 2.45 t km−1, whereas in tributaries, it was 126.94 and 34.05 t km−1, respectively. Total fine‐grained bed sediment storage averaged 563 t in the main channel and 6831 t in the catchment. The proportion of mean organic matter at individual sites was 15–47% and organic carbon 4–455 g C m−2, with both being highest in small headwater tributaries. Main channel bed sediment storage comprised 52% of mean annual suspended sediment flux and stored organic carbon comprised 7% of mean annual total organic carbon load. This indicates the importance of small headwater brooks for temporary within‐catchment storage of bed sediment and organic carbon and the significance of fine‐grained sediment stored in channels for the suspended sediment budget of boreal lowland rivers. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Combined anaerobic-aerobic and UV/H2O2 processes for the treatment of synthetic slaughterhouse wastewater

The biological treatment of a synthetic slaughterhouse wastewater (SSWW) is studied using an anaerobic baffled bioreactor (ABR) and an aerobic activated sludge (AS) at a laboratory scale in continuous mode. The total organic carbon (TOC) loading rate, the total nitrogen (TN) loading rate, and the flow rate are 0.03–1.01 g/(L.day), 0.01–0.19 g/(L.day), and 2.93–11.70 mL/min, respectively. The results reveal that combined anaerobic-aerobic processes had higher efficiency to treat SSWW than a single process. Up to 96.36% TOC, 80.53% TN, and 99.38% 5-day carbonaceous biochemical oxygen demand (CBOD5) removal from an influent concentration of 1,009 mgTOC/L, 420 mgTN/L, and 640 mgCBOD5/L at the hydraulic retention time (HRT) of 6.24 days and a flow rate of 3.75 mL/min are achieved. The UV/H2O2 process is studied to treat a secondary effluent of SSWW with TOC loadings of 65–350 mg/L. Up to 75.22% TOC and 84.38% CBOD5 removal are obtained at the HRT of 3 h with H2O2 concentration of 900 mg/L. Optimum molar ratios of 13.87 mgH2O2/mgTOCin and 4.62 mgH2O2/mgTOCin.h are also obtained. Combined anaerobic-aerobic and UV/H2O2 processes enhanced the biodegradability of the TOC, TN, and CBOD5 present in the SSWW. Up to 99.98% TOC, 82.84% TN, and 99.69% CBOD5 overall removals are obtained for an influent concentration of 1,005 mgTOC/L, 200 mgTN/L, and 640 mgCBOD5/L at the HRT of 4 days and a flow-rate of 5.90 mL/min.

Assessment of ecological quality status of Küçükçekmece Bay (Marmara Sea) by applying BENTIX, AMBI, BOPA and BO2A biotic indexes

This study was carried out to explore the effectiveness of different biotic indexes in the Marmara Sea. The assessment of ecological quality status (EQS) was performed by applying the biotic indexes BENTIX, AMBI, BOPA, BO2A and Shannon-Wienerdiversity, in combination with the estimation of total organic carbon (TOC) content of sediments. BOPA and BO2A indexes tended to overestimate the EQS of the stations. BENTIX was the most efficient index as it demonstrated conceivable EQS results with respect to TOC load and successfuly determined “acceptable” or “not acceptable” status of the stations. TOC content of sediment, which significantly correlated with several benthic measures (S, N, AMBI, BENTIX), proved to be a valuable proxy measure in evaluating the likelihood of benthic impairment. When overall EQS of northern Marmara Sea was discussed, the region was designated as ecologically disturbed with only 25.7% of the stations in acceptable status.

The impact of forest to urban land conversion on streamflow, total nitrogen, total phosphorus, and total organic carbon inputs to the converse reservoir, Southern Alabama, USA

High total organic carbon (TOC) concentrations in Converse Reservoir, a water source for Mobile, Alabama, have concerned water treatment officials due to the potential for disinfection byproduct (DBP) formation. TOC reacts with chlorine during drinking water treatment to form DBPs. This study evaluated how increased urbanization can alter watershed-derived total nitrogen (TN), total phosphorus (TP) and TOC inputs to the Converse Reservoir. Converse Watershed, on the urban fringe of Mobile, is projected to undergo urbanization increasing watershed urban land from 3% in 1992 to 22% urban land by 2020. A pre-urbanization scenario using 1992 land cover was coupled with 2020 projections of land use. The Loading Simulation Program C++ watershed model was used to evaluate changes in nutrient concentrations (mg L−1) and loads (kg) to Converse Reservoir. Urban and suburban growth of 52 km2 simulated from 1991 to 2005 (15 year) caused overall TN and TP loads to increase by 109 and 62%, respectively. Simulated urban growth generally increased monthly flows by 15%, but resulted in lower streamflows (2.9%) during drought months. Results indicate that post-urbanization median TN and TP concentrations were 59 and 66% higher than corresponding pre-urbanization concentrations, whereas TOC concentrations were 16% lower. An increase in urban flow caused TOC loads to increase by 26%, despite lower post-urbanization TOC concentrations.

Slaughterhouse wastewater treatment by combined anaerobic baffled reactor and UV/H 2O 2 processes

Combined processes of biological anaerobic baffled reactor (ABR) and UV/H 2O 2 at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater. In this study, the total organic carbon (TOC) loadings of 0.2–1.1 g/(L day) were used. The results revealed that combined processes had a higher efficiency to treat the synthetic slaughterhouse wastewater. Up to 95% TOC removal was obtained for an influent concentration of 973.3 mgTOC/L at the hydraulic retention time (HRT) of 3.8 days in the ABR and 3.6 h in the UV photoreactor. Meanwhile, up to 97.7% and 96.6% removal of chemical oxygen demand (COD) and 5-day carbonaceous biochemical oxygen demand (CBOD 5) were observed in the ABR for the same influent concentration, respectively. Comparatively, for an influent concentration of 157.6 mgTOC/L, the UV/H 2O 2 process alone with the TOC loading of 0.06–1.9 g/(L h) was also studied, in which, up to 64.3%, 83.7%, and 84.3% of TOC, COD, and CBOD 5 removal were observed, respectively, at the HRT of 2.5 h with hydrogen peroxide (H 2O 2) concentration of 529 mg/L. It was found that individual ABR and UV/H 2O 2 processes enhanced the biodegradability of the treated effluent by an increased CBOD 5/COD ratio of 0.4 to 0.6. An optimum H 2O 2 dosage of 3.5 (mgH 2O 2)/(mgTOC in h) was also found for the UV/H 2O 2 process.

Implications of organic carbon in the deterioration of water quality in reclaimed water distribution systems

Changes in water quality in reclaimed water distribution systems are a major concern especially when considering the potential for growth of pathogenic microbes. A survey of 21 wastewater process configurations confirmed the high quality effluent produced using membrane bioreactor (MBR) technology, but suggests that other technologies can be operated to produce similar quality. Data from an intensive twelve-month sampling campaign in four reclaimed water utilities revealed the important trends for various organic carbon parameters including total organic carbon (TOC), biodegradable dissolved organic carbon (BDOC), and assimilable organic carbon (AOC). Of the four utilities, two were conventional wastewater treatment with open reservoir storage and two employed MBR technology with additional treatment including UV, ozone, and/or chlorine disinfection. Very high BDOC concentrations occurred in conventional systems, accounting for up to 50% of the TOC loading into the system. BDOC concentrations in two conventional plants averaged 1.4 and 6.3 mg/L and MBR plants averaged less than 0.6 mg/L BDOC. Although AOC showed wide variations, ranging from 100 to 2000 μg/L, the AOC concentrations in the conventional plants were typically 3–10 times higher than in the MBR systems. Pipe-loop studies designed to understand the impact of disinfection on the microbiology of reclaimed water in the distribution system revealed that chlorination will increase the level of biodegradable organic matter, thereby increasing the potential for microbial growth in the pipe network. This study concludes that biodegradable organic carbon is an important factor in the microbial quality and stability of reclaimed water and could impact the public health risk of reclaimed water at the point of use.

Membrane-attached biofilm as a mean to facilitate nitrification in activated sludge process and its effect on the microfaunal population

A membrane-attached biofilm (MAB) was incorporated into a conventional activated sludge (AS) process to facilitate the nitrification. The simultaneous carbon removal and nitrification of the MAB incorporated AS (AS + MAB) process was compared with that of the AS process. The total organic carbon (TOC) loading was varied from 0.43 to 0.68 g/(L d), and the corresponding total nitrogen (T-N) loading was varied from 0.15 to 0.24 g/(L d) with keeping the C/N ratio at 2.85. The TOC removal efficiencies were above 95% for both processes within the range of TOC loading tested. The results showed the excellent carbon removal in both processes. The volumetric nitrification rate of AS + MAB process was about 0.14 g/(L d) at the T-N loading of 0.21 g/(L d), and was about seven times higher than that of AS process at the loading of 0.22 g/(L d). The results clearly demonstrated that the MAB facilitated the nitrification in the AS process. The maximum surface nitrification rate was about 8.4 g/(m 2 d), which was based on the surface area of the biofilm module. This value was almost comparable to that of nitrifying MAB under the same T-N loading, indicating little carbon inhibition against the nitrification in the AS + MAB process. On the other hand, the presence of MAB enabled the growth of slow-growing microorganisms not only nitrifying bacteria but also microfauna. The enumeration of microfauna in bulk suspension was carried out for both processes during the treatment. The abundance in rotifers, in addition to the appearance of oligochaetes, in the AS + MAB process suggested the less sludge generation due to the enlarged food-chain. The incorporation of MAB into AS process enabled the simultaneous nitrification and carbon removal, and had high potential in less sludge generation.

Start-up and Performance of a Novel Reactor—Jet Biogas Inter-loop Anaerobic Fluidized Bed

A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed (JBILAFB), was designed and constructed. The start-up and performance of the reactor was investigated in the process of artificial glucose wastewater treatment. With the wastewater recycle ratio of 2.5 : 1, the recycled wastewater with biogas could mix sludge and wastewater in the JBILAFB reactor completely. The start-up of the JBILAFB reactor could be completed in less than 70 d through maintenance of hydraulic retention time (HRT) and stepwise increase of feed total organic carbon (TOC) concentration. After the start-up, with the volumetric TOC loadings of 14.3 kg·m −3·d −1, the TOC removal ratio, the effluent pH, and the volatile fatty acids (VFA)/alkalinity of the JBILAFB reactor were more than 80%, close to 7.0 and less than 0.4, respectively. Moreover, CH 4 was produced at more than 70% of the theoretical value. The reactor exhibited high stability under the condition of high volumetric TOC loading. Sludge granules in the JBILAFB reactor were developed during the start-up and their sizes were enlarged with the stepwise increase of volumetric TOC loadings from 0.8 kg·m −3·d −1 to 14.3 kg·m −3·d −1. Granules, an offwhite color and a similar spherical shape, were mainly comprised of global-like bacteria. These had good methanogenic activity and settleability, which were formed probably through adhesion of the bacteria. Some inorganic metal compounds such as Fe, Ca, Mg, Al, etc. were advantageous to the formation of the granules.

Effects of Urbanization on Organic Carbon Loads in the Sacramento River, California

To gain better understanding of the effects of urbanization on organic matter transport in rivers, we quantified total organic carbon loading from point and non‐point urban sources within the metropolitan area of Sacramento and compared these loads to the amount of organic carbon carried in the downstream Sacramento River. Median total organic carbon (TOC) concentrations in the Sacramento River, non‐point urban runoff and wastewater treatment plant effluent were 2.1, 8.9, and 23 mg L−1, respectively. Dissolved organic carbon (DOC) in non‐point runoff and the river had similar specific UVA absorbance and disinfection by‐product formation potential, but based on radiocarbon measurements, non‐point DOC was substantially older (age &gt; 2000 a) than DOC in the Sacramento River. This finding suggests that DOC in non‐point runoff is derived primarily from leaching of older soil organic matter. The 10th, 50th, 90th and 99th percentile contributions of urban sources to daily TOC load in the Sacramento River were 10%, 20%, 38% and 80%, respectively. Total urban TOC yield was 150 kg ha−1yr−1 and urban sources contributed ∼17% of the annual load of TOC in the Sacramento River below Sacramento.