Determination of the potential of pickle wastewater as feedstock for biopolymer production.

Food industry wastewater (FIWW) streams with high organic content are among the most suitable and inexpensive candidates for polyhydroxyalkanoate (PHA) biopolymer production. Due to its high organic acid content, pickle industry wastewater (PIWW), can be considered as one of the prospective alternatives to petroleum-based polymers for PHA production. In this context, this study aimed to investigate the production of PHA with enriched microbial culture using PIWW. Two laboratory scale sequencing batch reactors (SBRs) were operated under aerobic dynamic feeding conditions at a sludge retention time of 8 days, with a total cycle duration of 24 hours. SBRs were fed with peptone mixture and PIWW. In-cycle analysis and batch respirometric tests were performed to evaluate PHA storage together with biodegradation kinetics. In-cycle analysis showed that maximum PHA content was 1,820 mgCOD/L, corresponding to 44% in the biomass (ratio of chemical oxygen demand (COD) to volatile suspended solids) for PIWW. Experimental results were also confirmed with activated sludge model simulations. As for the PHA composition, hydroxybutyrate was the major fraction. Model simulations proposed a unique conversion-degradation-storage pathway for the organic acid mixture. This paper presents a novel insight for better understanding of PHA biopolymer production using high saline FIWW.

Impact of aerobic stabilization on the characteristics of treatment sludge in the leather tanning industry.

The efficiency of aerobic stabilization on the treatment sludge generated from the leather industry was investigated to meet the expected characteristics and conditions of sludge prior to landfill. The sludge types subjected to aerobic stabilization were chemical treatment sludge, biological excess sludge, and the mixture of both chemical and biological sludges. At the end of 23 days of stabilization, suspended solids, volatile suspended solids and total organic carbon removal efficiencies were determined as 17%, 19% and 23% for biological sludge 31%, 35% and 54% for chemical sludge, and 32%, 34% and 63% for the mixture of both chemical and biological sludges, respectively. Model simulations of the respirometric oxygen uptake rate measurements showed that the ratio of active biomass remained the same at the end of the stabilization for all the sludge samples. Although mixing the chemical and biological sludges resulted in a relatively effective organic carbon and solids removal, the level of stabilization achieved remained clearly below the required level of organic carbon content for landfill. These findings indicate the potential risk of setting numerical restrictions without referring to proper scientific support.

Effects of potential inducers to enhance laccase production and evaluating concomitant enzyme immobilisation.

This work investigated non-polar solvent hexane and polar solvents methanol and ethanol as inducers besides a well-known inducer, copper, for laccase production with and without mesoporous silica-covered plastic packing under sterilised and unsterilised conditions. The potential of waste-hexane water, which is generated during the mesoporous silica production process, was also investigated as a laccase inducer. During the study, the free and immobilised laccase activity on the packing was measured. The results showed that the highest total laccase activity, approximately 10,000 Units, was obtained under sterilised conditions with 0.5 mM copper concentration. However, no immobilised laccase activity was detected except in the copper and ethanol sets under unsterilised conditions. The maximum immobilised laccase activity of the sets that used waste hexane as an inducer was 1.25 U/mg packing. According to its significant performance, waste hexane can be an alternative inducer under sterilised conditions. Concomitant immobilised packing showed satisfactory laccase activities and could be a promising method to reduce operation costs and improve the cost-efficiency of enzymatic processes in wastewater treatment plants.

Insights into the acute effect of anti-inflammatory drugs on activated sludge systems with high solids retention time.

The increase in the occurrence of the pharmaceuticals in the environmental compartments is becoming emerging concern as it reflects their inefficient treatment in the wastewater treatment plants which are the main sources of these micropollutants. Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the most commonly prescribed and frequently detected pain medications in wastewater treatment plants. A lab scale sequencing batch reactor (SBR) was operated for seven months and acute inhibitory effect of NSAIDs on activated sludge was tested with respirometry. Culture amendment with different concentrations of NSAIDs in the presence as well as absence of nitrification inhibitor resulted in considerable variation in the oxygen uptake rate (OUR) profiles. The decrease in OUR and nitrate production rate governed with reduced heterotrophic and nitrification activity. The kinetics of half saturation for growth and maximum autotrophic growth rates are determined to be affected negatively by the acute impact of anti-inflammatory pharmaceuticals even at the environmentally relevant concentrations. High removal of tested NSAIDs was observed even for the first time introduce with these compounds.

Impact of ultrasonic pre-treatment on domestic sludge digestion performance and microbial community dynamics.

Ultrasonication-assisted sludge digestion technology is a lately used alternative sludge treatment method in wastewater treatment plants (WWTPs). This study focused on determining the influence of ultrasonication on aerobic and anaerobic sludge digestion, two most commonly used sludge handling processes, as well as on the investigation of microbial community structure after digestion. The effect of ultrasonication as a pre-treatment technique prior to sludge digestion on microbial population dynamics was not yet investigated comprehensively. Sludge sample taken from the primary and secondary settling tanks of a domestic wastewater treatment plant was used during the experiments. Based on the relevant data, while applied ultrasonication did not improve the anaerobic digestion efficiency, progress was achieved in the sludge dewaterability characteristics at the end of aerobic digestion. According to the results of both denaturant gradient gel electrophoresis and pyrosequencing data, ultrasonic pre-treatment decreased the richness of the microbial population in aerobic digestion, whereas increased the biocomplexity of the population in anaerobic digestion. We revealed that sludge pre-treatment with ultrasonication does not always improve the digestion performance. Composition of the sludge was the main factor defining the digestion performance.

Biodegradability and denitrification potential of settleable chemical oxygen demand in domestic wastewater.

The effect of settling on mass balance and biodegradation characteristics of domestic wastewater and on denitrification potential was studied primarily using model calibration and evaluation of oxygen uptake rate profiles. Raw domestic wastewater was settled for a period of 30 minutes and a period of 2 hours to assess the effect of primary settling on wastewater characterization and composition. Mass balances in the system were made to evaluate the effect of primary settling on major parameters. Primary settling of the selected raw wastewater for 2 hours resulted in the removal of 32% chemical oxygen demand (COD), 9% total Kjeldahl nitrogen, 9% total phosphorus, and 47% total suspended solids. Respirometric analysis identified COD removed by settling as a new COD fraction, namely settleable slowly biodegradable COD (X(ss)), characterized by a hydrolysis rate of 1.0 day(-1) and a hydrolysis half-saturation coefficient of 0.08. A model simulation to test the fate and availability of suspended (X(s)) and settleable (X(ss)) COD fractions as carbon sources for denitrification showed that both particulate COD components were effectively removed aerobically at sludge ages higher than 1.5 to 2.0 days. Under anoxic conditions, the biodegradation of both COD fractions was reduced, especially below an anoxic sludge retention time of 3.0 days. Consequently, modeling results revealed that the settleable COD removed by primary settling could represent up to approximately 40% of the total denitrification potential of the system, depending on the specific configuration selected for the nitrogen removal process. This way, the results showed the significant effect of primary settling on denitrification, indicating that the settleable COD fraction could contribute an additional carbon source in systems where the denitrification potential associated with the influent becomes rate-limiting for the denitrification efficiency.

Temperature and pH effect on the microbial reductive transformation of pentachloronitrobenzene.

The effect of pH and temperature on the microbial reductive transformation of pentachloronitrobenzene (PCNB), an organochlorine fungicide, was investigated with a mixed fermentative/methanogenic culture developed from a contaminated estuarine sediment. Culture series were incubated at a temperature range from 4 to 45 degrees C at pH 6.9+/-0.1 and at a pH range from 2.7+/-0.1 to 7.6+/-0.1 at 22 degrees C. Significant differences were observed in terms of biotransformation rate, extent, and products as a function of temperature. Incubation at different pH values resulted in differences in biotransformation rate and extent, but not in terms of products formed. PCNB (3 microM) was transformed to pentachloroaniline (PCA) in all culture series. However, sequential dechlorination of PCA was observed only at a temperature range from 4 to 35 degrees C and at a pH range from 6.2+/-0.1 to 7.6+/-0.1. The highest PCA dechlorination rate was observed at 22 degrees C and at pH 7.6+/-0.1. The effect of temperature on the PCA dechlorination rate was modeled using an Arrhenius relationship, which accounts for both enzyme activation and deactivation. The dechlorination of PCA and chlorinated aniline intermediates was simulated using a branched-chain Michaelis-Menten model, and kinetic constants were determined.

Respirometric assessment of aerobic sludge stabilization.

Aerobic sludge stabilization was assessed respirometrically with the sludge taken from the secondary settling tank of a domestic wastewater treatment facility in Istanbul, Turkey. Zero-order removal rates of 178, 127 and 44 mg/L day were found for Suspended Solids (SS), Volatile Suspended Solids (VSS) and Total Organic Carbon (TOC) at the end of 18 days sludge stabilization, respectively. Significant nutrient release was observed by the mineralized nitrogen and phosphorus from the death and lysis of microorganisms. The model simulations for the batch respirometric assays for initial, 7th and 18th days of the stabilization agree reasonably well with the experimental data. The maximum storage rates (k(sto)) as well as maximum growth rates on stored products (micro(H2)) decrease with increasing stabilization period. Respirometric assays indicated the presence of microorganisms that started to compete with the dominant microorganisms as a result of the stabilization. As such, these findings have significance in terms of the efforts related to the sludge management and application processes.

Influence of pH and temperature on soluble substrate generation with primary sludge fermentation.

The study was undertaken to evaluate the effect of pH and temperature control on the generation of soluble fermentation products from primary sludge. The effect was tested by running parallel experiments under pH and temperature controlled and uncontrolled conditions. In fermentation experiments conducted at 20 degrees C without pH control, the average soluble COD release was 14 mg per liter of wastewater treated, representing a potential increase of 5% in the biodegradable COD content of the primary sedimentation effluent. The corresponding average VFA generation was 9.2mg COD l(-1). The nutrient release was practically negligible and stayed at 0.4 mg l(-1) for nitrogen and 0.1mg l(-1) for phosphorus. Acetic acid accounted more than 45% of the generated VFA in all experimental runs. The acetic acid content of the VFA decreased with increasing initial VSS concentrations and higher pH levels. VFA generation by fermentation was significantly affected with temperature and pH control. Temperature change between 10 and 24 degrees C induced a five-fold increase in VFA generation, from 610 mg l(-1) at 10 degrees C to 2950 mg l(-1) at 24 degrees C.

Effect of nitrate reduction on the microbial reductive transformation of pentachloronitrobenzene.

The effect of nitrate reduction onthe reductive biotransformation of pentachloronitrobenzene (PCNB), an organochlorine fungicide, was assessed with a mixed fermentative/methanogenic culture enriched from a contaminated estuarine sediment. Glucose and methanol served asthe electron and carbon source. PCNB at an initial concentration of 3 microM was transformed to pentachloroaniline (PCA) simultaneously with nitrate reduction in cultures amended with 10 to 200 mg N/L nitrate. PCA sequentially dechlorinated to dichlorinated anilines (mainly 2,5-DCA) in the nitrate-free control culture, and the culture which was amended with 10 mg N/L nitrate. PCA partially dechlorinated to tetrachloroanilines (TeCAs), and methanogenesis was completely inhibited in the cultures amended with 50-200 mg N/L nitrate, whereas fermentation was only inhibited in the cultures amended with 200 mg N/L nitrate. The impact of nitrate reduction on the sequential dechlorination of PCA was attributed to the production of nitric oxide (NO) and nitrous oxide (N2O). Partial nitrate reduction to ammonia was observed in the cultures amended with 50, 100, or 200 mg N/L nitrate and PCNB (3 microM). Therefore, nitrate concentrations at or above 50 mg N/L lead to accumulation of toxic compounds such as highly chlorinated anilines (i.e., PCA, TeCAs) and denitrification intermediates (i.e., NO, N2O). These findings have significant environmental implications in terms of the fate and transformation of PCNB in subsurface environments where nitrate is present.

Thermophilic bacteria in cool temperate soils: are they metabolically active or continually added by global atmospheric transport?

Thermophilic soil geobacilli isolated from cool temperate geographical zone environments have been shown to be metabolically inactive under aerobic conditions at ambient temperatures (-5 to 25 degrees C). It is now confirmed that a similar situation exists for their anaerobic denitrification activity. It is necessary therefore to determine the mechanisms that sustain the observed significant viable populations in these soils. Population analysis of thermophiles in rainwater and air samples has shown different species compositions which support the view that long distance global transport and deposition in rainwater is a possible source of replenishment of the soil thermophile populations. Survival experiments using a representative Geobacillus isolate have indicated that while cells lose viability rapidly at most temperatures, populations can increase only when the temperature allows growth to take place at a rate which exceeds death rate. Long term (9-month) experiments at 4 degrees C show population increases which can be accounted for by very slow growth rates complemented by negligible death rates. These results are interpreted in the context of current hypotheses on the biogeography patterns of bacteria.

Kinetics of the microbial reductive dechlorination of pentachloroaniline.

The microbial reductive dechlorination kinetics of pentachloroaniline (PCA) and less chlorinated anilines (CAs) were investigated with a mixed, fermentative/ methanogenic culture. Batch dechlorination assays were performed with all available CAs at an initial concentration of 3 microM, and an incubation temperature of 22 degrees C. Dechlorination of PCA, two tetrachloroanilines (2,3,4,5- and 2,3,5,6-TeCA), five trichloroanilines (2,3,4-, 2,3,5-, 2,4,5-, 2,4,6-, and 3,4,5-TrCA), and one dichloroaniline (3,5-DCA; low extent) was observed but none of the five remaining dichloroanilines and three monochloroanilines were dechlorinated by the enrichment culture during batch assays. The dechlorination rates (k') and half-saturation coefficients (Kc) were measured using nonlinear regression based on the integrated Michaelis-Menten equation under conditions of electron donor saturation and assuming constant biomass concentration over the relatively short batch incubation period. At an initial concentration of CAs of about 3 microM, the values of k' and Kc ranged from 0.25 to 1.19 microM/day and from 0.11 to 1.72 microM, respectively, corresponding to half-lives in the range of 1.5-8.5 days. Model simulations of the sequential dechlorination reactions based on a branched-chain Michaelis-Menten model and using independently measured k' and Kc values matched the experimental data very well.

Microbial reductive transformation of pentachloronitrobenzene under methanogenic conditions.

The reductive transformation of pentachloronitrobenzene (PCNB), an organochlorine fungicide, was investigated with a mixed, methanogenic culture developed from a contaminated estuarine sediment. Batch assays performed with this enrichment culture resulted in the biotransformation of PCNB to pentachloroaniline (PCA), which was then sequentially dechlorinated as follows: PCA --> 2,3,4,5- and 2,3,5,6-tetrachloroaniline (TeCA) --> 2,4,5- and 2,3,5-trichloroaniline (TrCA) --> 2,4-, 2,5-, and 3,5-dichloroaniline (DCA) --> 3- and 4-chloroaniline (CA) (low levels). Glucose fermentation, methanogenesis, and dechlorination were not inhibited at an initial PCNB concentration up to 40 microM, which is 27 times higher than its aqueous solubility. The addition of 25 mM 2-bromoethanesulfonate (BES) to the PCNB-amended culture resulted in the complete inhibition of methanogenesis, but the biotransformation of PCNB to PCA and its sequential dechlorination pathway were not affected. The addition of sodium azide (200 mg/L) to the PCNB-amended culture resulted in complete inhibition of methanogenesis, but did not inhibit the transformation of PCNB to PCA; however, PCA dechlorination was not observed. PCNB was also abiotically transformed to PCA in autoclaved culture media but at much lower rates as compared to the biotic assays. In contrast, the rate of PCNB to PCA transformation in autoclaved culture controls was similar to the rates observed in the azide-amended culture and the active enrichment culture, indicating that biotically derived reductants facilitated the observed transformation of PCNB to PCA. Dechlorination of PCA was not observed in any of the abiotic controls. These findings have significant environmental implications in terms of the fate and transport of PCNB, PCA, and its dechlorination products in subsurface systems.