Delia Teresa Sponza

Extracellular polymer substances and physicochemical properties of flocs in steady- and unsteady-state activated sludge systems

Abstract The content of protein, polysaccharide and DNA were quantified in four different industries and municipal sludge flocs by continuous operation of five lab-scale activated sludge reactors under steady- and unsteady-state conditions. Physicochemical properties such as surface charge, bound water and contact angle in floc biomass were determined under both conditions. The effect of anaerobic conditions and nutrient deficiencies on the floc surface properties were investigated. Extracellular polymer substances (EPS) analysis showed that between 70 and 80% of the extracellular organic material could be attributed to protein. Lower amounts of protein and high DNA levels were found in the extracellular substances from flocs grown on more complex organics and substrates. Changing the wastewater from chemical, leather and dye to that of the wine industry and municipal treatment plants resulted in an increase in protein and a decrease in DNA level of floc EPSs. Good settling characteristics were observed in both wine industry and municipal activated sludge samples and this was associated with high negative charged floc surface and both lower bound water and contact angle containing floc EPS. Low protein and high DNA level in EPS is associated with both high contact angle, bound water and low negative charges in activated sludge samples. This is associated with high sludge volume index (SVI) value, indicating poor settleability. In all samples, low SVI values were associated with a high negatively charged floc surface and low contact angle and bound water containing floc EPS. Hydrophobicity (large contact angles) of flocs is obtained with high SVI containing activated sludge samples. Increases in protein and polysaccharide levels in EPS floc were observed at sequential low/high F/M ratios and low dissolved oxygen concentrations. In contrast, decreases in protein and polysaccharide amounts were obtained under anaerobic conditions. Nitrogen deficiency increased the protein level in the EPS and was associated with good settling (low SVI) and high negatively charged floc surfaces while phosphorous deficiency decreased the protein content of EPS and surface charge of flocs in activated sludge.

Effect of oxygen on decolorization of azo dyes by Escherichia coli and Pseudomonas sp. and fate of aromatic amines

The degradation of two azo dyes; Congo Red (CR) and Direct Black 38 (DB 38), in use in textile industries in Turkey, were investigated using two facultative microorganisms (Escherichia coli and Pseudomonas sp. ) under anaerobic, aerobic, and microaerophilic conditions. Hundred milligram per litre of dyes and 1000 mg glucose-COD/l containing basal medium were used and were incubated for 5 and 9 days. Simultaneous biomass activity and colour removal performance, was monitored during batch assays. The effects of two different microorganisms and aerobic/anaerobic conditions on decolorization were recorded with the monitoring of colour, pH, COD, dissolved oxygen, alkalinity, and volatile fatty acids concentrations. The aromatic amines (as benzidine) arising from the metabolites of anaerobic biodegradation of dyes and the recoveries of these aromatic amines were also monitored. High benzidine recoveries indicated the accumulation of aromatic amines under aerobic conditions. The colour of the CR and DB 38 dyes were removed up to 98 and 72%, respectively, by E. coli at the end of anaerobic incubation, while no decolorization occurred throughout the aerobic incubation. Under microaerophilic conditions, the azo dyes CR and DB 38 were decolorized up to 39 and 75% by E. coli, respectively. In studies with Pseudomonas sp., the colour of the CR and DB 38 dyes were removed up to 100 and 83%, respectively, after 5 days of anaerobic incubation, while 76 and 74% colour removal efficiencies were observed under microaerophilic conditions. # 2002 Elsevier Science Ltd. All rights reserved.

Application of toxicity tests into discharges of the pulp-paper industry in Turkey

The aim of this study was to investigate the acute toxicity of pulp-paper industry wastewater using traditional and enrichment toxicity tests and to emphasize the importance of toxicity tests in wastewater discharge regulations. Enrichment toxicity tests are novel applications and give an idea of whether there is potential toxicity or growth-limiting and -stimulating conditions. Different organisms were used such as bacteria (floc and coliform bacteria), algae (Chlorella sp.), protozoa (Vorticella sp.), and fish (Lepistes sp.) to represent four trophic levels. Furthermore, chemical oxygen demand (COD) fractionation results were compared with these tests to assess the effect of COD subcategories on the determination of possible toxicity. The pulp-paper industry results revealed acute toxicity to at least two organisms in 6 of 20 effluent samples. The toxicity test results were assessed with chemical analyses such as COD, biochemical oxygen demand (BOD), color, absorbable organic halogen (AOXs), and phenol. It was observed that the toxicity of the effluents could not be explained by using physicochemical analyses in four cases for the pulp-paper industry. The results clearly indicate that bioassay tests provide additional information on the toxicity potential of industrial discharges and effluents.

Effect of rhamnolipid on the aerobic removal of polyaromatic hydrocarbons (PAHs) and COD components from petrochemical wastewater.

The removal efficiencies of 15 PAHs and some COD components (inert, readily degradable, slowly degradable and metabolic products) from a wastewater taken from a petrochemical industry treatment plant (Izmir, Turkey) have been determined using an aerobic completely stirred tank reactor (CSTR). Addition of rhamnolipid surfactant (15 mg l(-1)) increased the removal efficiencies of PAHs and soluble COD from 72% and 90% to 80% and 99%, respectively. The rhamnolipid treatment caused a significant increase of 5- and 6-ring PAH degradation. The soluble COD removal efficiency was 93%, in CSTR reactors with rhamnolipid added. The inert COD removal efficiency was 60% in a CSTR reactor containing rhamnolipid. Batch tests showed that removal arising from the adsorption of the PAHs was low (between 1.88% and 4.84%) while the removal of PAHs from the petrochemical industry wastewater via volatilization varied between 0.69% and 5.92%. Low sorption capacity (K(p)) values for refinery activated sludge (approximately 2.98 l g(-1)) confirmed that bio-sorption was not an important mechanism controlling the fate of PAHs in aerobic CSTR reactors. Models proposed to simulate the PAH removal indicated that 94% of the PAHs were removed via biodegradation.

Necessity of toxicity assessment in Turkish industrial discharges (examples from metal and textile industry effluents).

Toxicity of some organic and inorganic chemicals to microorganisms is an important consideration in assessingtheir environmental impact against their economic benefits.Microorganisms play an important role in several environmentalprocesses, both natural and engineered. Some organic and inorganics at toxic levels have been detected in industrial discharges resulting in plant upsets and discharge permit violations. In addition to this, even though in some cases the effluent wastewater does not exceed the discharge limits,the results of toxicity tests show potential toxicity. Toxicityknowledge of effluents can benefit treatment plant operators inoptimising plant operation, setting pre-treatment standards, and protecting receiving water quality and in establishing sewer discharge permits to safeguard the plant. In the Turkish regulations only toxicity dilution factor (TDF) with fish is part of the toxicity monitoring program of permissible wastewater discharge. In various countries, laboratory studiesinvolving the use of different organisms and protocol for toxicity assessment was conducted involving a number of discharges.In this study, it was aimed to investigate the acute toxicity of textile and metal industry wastewaters by traditional and enrichment toxicity tests and emphasize the importance of toxicity tests in wastewater discharge regulations. The enrichment toxicity tests are novel applications and give anidea whether there is potential toxicity or growth limiting and stimulation conditions. Different organisms were used suchas bacteria (Floc and Coliform bacteria) algae (Chlorella sp.), fish (Lepistes sp.) and protozoan (Vorticella sp.) to represent four tropic levels. The textile industry results showed acute toxicity for at least one organism in 8 out of 23 effluent samples. Acute toxicity for at least two organisms in 7 out of 23 effluent sampling was observed for the metal industry. The toxicity test results were assessed with chemical analyses such as COD, BOD, color and heavy metals. It was observed that the toxicity of the effluents could not be explained by using physicochemical analyses in 5 cases for metal and 4 cases for the textile industries. The results clearly showed that the useof bioassay tests produce additional information about the toxicity potential of industrial discharges and effluents.

Decolorization of azo dyes under batch anaerobic and sequential anaerobic/aerobic conditions

Abstract Batch anaerobic and sequential anaerobic upflow anaerobic sludge blanket (UASB)/aerobic continuous stirred tank reactor (CSTR) were used to determine the color and COD removals under anaerobic/aerobic conditions. Two azo dyes namely “Reactive Black 5 (RB 5),” “Congo Red (CR),” and glucose as a carbon source were used for synthetic wastewater. The course of the decolorization process approximates to first order and zero order kinetics with respect to dye concentration for RB 5 and Congo Red azo dyes, respectively, in batch conditions. The decolorization kinetic constant (K 0) values increased from 3.6 to 11.8 mg (L h)−1 as increases in dye concentrations from 200 to 3200 mg L−1 for CR. Increases in dye concentrations from 0 to 3200 mg L−1 reduce the decolorization rate constant (k 1) values from 0.0141 to 0.0019 h−1 in batch studies performed with RB 5. Decolorization was achieved effectively under test conditions but ultimate decolorization of azo dyes was not observed at all dye concentrations in batch assay conditions. Dye concentrations of 100 mg L−1 and 3000 mg L−1 of glucose–COD containing basal medium were used for continuous studies. The effect of organic loadings and HRT, on the color removal efficiencies and methane gas productions were monitored. 94.1–45.4% COD and 79–73% color removal efficiencies were obtained at an organic system during decolorization of Reactive Black 5. 92.3–77.0% COD and 95.3–92.2% decolorization efficiencies were achieved at a organic loading rate of 1.03–6.65 kg (m3 day)−1 and a HRT of 3.54–0.49 for Congo Red treatment. The results of this study showed that, although decolorization continued, COD removal efficiencies and methane gas production were depressed at high organic loadings under anaerobic conditions. Furthermore, VFA accumulation, alkalinity consumption, and methane gas percentage were monitored at organic loading as high as 2.49–4.74 kg (m3 day)−1 and 24.60–30.62 kg (m3 day)−1, respectively, through the decolorization of RB 5 and CR dyes in the UASB reactor.

Kinetics of para-nitrophenol and chemical oxygen demand removal from synthetic wastewater in an anaerobic migrating blanket reactor.

A laboratory scale anaerobic migrating blanket reactor (AMBR) was operated at different HRTs (1-10.38 days) in order to determine the para-nitrophenol (p-NP) and COD removal kinetic constants. The reactor was fed with 40 mg L(-1)p-NP and 3000 mg L(-1) glucose-COD. Modified Stover-Kincannon and Grau second-order kinetic models were applied to the experimental data. The predicted p-NP and COD concentrations were calculated using the kinetic constants. It was found that these data were in better agreement with the observed ones in the modified Stover-Kincannon compared to Grau second-order model. The kinetic constants calculated according to Stover-Kincannon model are as follows: the saturation value constant (K(B)) and maximum utilization rate constants (R(max)) were found as 31.55 g CODL(-1)day(-1), 29.49 g CODL(-1)day(-1) for COD removal and 0.428 g p-NPL(-1)day(-1), 0.407 g p-NPL(-1)day(-1) for p-NP removal, respectively (R(2)=1). The values of (a) and (b) were found to be 0.096 day and 1.071 (dimensionless) with high correlation coefficients of R(2)=0.85 for COD removal. Kinetic constants for specific gas production rate were evaluated using modified Stover-Kincannon, Van der Meer and Heerrtjes and Chen and Hasminoto models. It was shown that Stover-Kincannon model is more appropriate for calculating the effluent COD, p-NP concentrations in AMBR compared to the other models. The maximum specific biogas production rate, G(max), and proportionality constant, G(B), were found to be 1666.7 mL L(-1) day(-1) and 2.83 (dimensionless), respectively in modified Stover-Kincannon gas model. The bacteria had low Haldane inhibition constants (K(ID)=14 and 23 mg L(-1)) for p-NP concentrations higher than 40 mg L(-1) while the half velocity constant (K(s)) increased from 10 to 60 and 118 mg L(-1) with increasing p-NP concentrations from 40 to 85 and 125 mg L(-1).

Effects of nitrobenzene concentration and hydraulic retention time on the treatment of nitrobenzene in sequential anaerobic baffled reactor (ABR)/continuously stirred tank reactor (CSTR) system.

The effects of increasing nitrobenzene (NB) concentrations and hydraulic retention times (HRT) on the treatment of NB were investigated in a sequential anaerobic baffled reactor (ABR)/aerobic completely stirred tank reactor (CSTR) system. In the first step of the study, the maximum COD removal efficiencies were found as 88% and 92% at NB concentrations varying between 30 mg L(-1) and 210 mg L(-1) in ABR. The minimum COD removal efficiency was 79% at a NB concentration of 700 mg L(-1). The removal efficiency of NB was nearly 100% for all NB concentrations in the ABR reactor. The methane gas production and the methane gas percentage remained stable (1500 mL day(-1) and 48-50%, respectively) as the NB concentration was increased from 30 to 210 mg L(-1). In the second step of the study it was found that as the HRT decreased from 10.38 days to 2.5 days the COD removal efficiencies decreased slightly from 94% to 92% in the ABR. For maximum COD and NB removal efficiencies the optimum HRT was found as 2.5 days in the ABR. The total COD removal efficiency was 95% in sequential anaerobic (ABR)/aerobic (CSTR) reactor system at a minimum HRT of 1 day. When the HRT was decreased from 10.38 days to 1 day, the methane percentage decreased from 42% to 29% in an ABR reactor treating 100 mg L(-1) NB. Nitrobenzene was reduced to aniline under anaerobic conditions while aniline was mineralized to catechol with meta cleavage under aerobic conditions.

Anaerobic granule formation and tetrachloroethylene (TCE) removal in an upflow anaerobic sludge blanket (UASB) reactor

Abstract The granulation process was examined using synthetic wastewater containing tetrachloroethylene (TCE) in a 2 liters laboratory upflow anaerobic sludge blanket (UASB) reactor. The anaerobic biotransformation of TCE was investigated during the granulation process by reducing the HRT and increasing the chemical oxygen demand (COD) and TCE loadings. Anaerobic unacclimated sludge and glucose were used as seed and primary substrate, respectively. Massive initial granules were developed after 1.5 months of start-up, which grew at an accelerated pace for 7 months and then became fully grown. The effect of operational parameters such as influent TCE concentrations, COD and TCE loading, food to microorganism (F/M) ratio and specific methanogenic activity (SMA) were also considered during granulation. The granular sludge cultivated had a maximum diameter of 2.5 mm and SMA of 1.32 g COD (gTSS.day) −1 . COD and TCE removal efficiencies of 92% and 88% were achieved when the reactor was operating at TCE and COD loading rates of 30 mg (l.day) −1 and 10.5 g (l.day) −1 , respectively. This corresponds to HRT of 0.40 day and F/M ratio of 1.28 gCOD (gTSS.day) −1 . Kinetic coefficients of k (maximum specific substrate utilization rate), K s (half velocity coefficient), Y (growth yield coefficient) and b (decay coefficient) were determined to be 2.38 mgCOD (mgTSS.day) −1 , 108 mgCOD l −1 , 0.17 mgTSS (mgCOD) −1 and 0.015 day −1 , respectively for TCE biotransformation together with glucose as carbon and energy source during granulation.

Aromatic Amine Degradation in a UASB/CSTR Sequential System Treating Congo Red Dye

Abstract In this study an anaerobic (upflow anaerobic sludge blanket reactor)/aerobic (completely stirred tank reactor) sequential system was used to treat a synthetic wastewater with minerals and co-substrate together with 100–4000 mg L−1 of Congo Red dye (Direct red 28) (CR), which is a banned azo dye in Turkey. The effect of hydraulic retention time (HRT) on the decolorization and the COD removal efficiency was investigated at constant 100 mg L−1 Congo Red concentration. 77% of COD and 95% of color was removed at a HRT of 0.486 days and a maximum organic loading rate of 6.656 kg COD m−3 day−1 in the anaerobic/aerobic stage. In the continuous operations, 88% of COD, 99% of color and 91% of total aromatic amine (TAA) were removed at a HRT of 3.60 days and at a CR concentration of 4000 mg L−1. This corresponds to an organic loading rate of 1.81 kg COD m−3 day−1, and a CR dye loading rate of 46.37 g dye m−3 h−1, respectively, in the whole system. The TAA produced under anaerobic conditions was ultimately removed in the aerobic stage, resulting in very low aromatic amine recoveries (5–18%) in the last one. Therefore the aerobic effluents exhibited higher IC50 and specific methanogenic activities (SMA) compared to anaerobic and dye containing samples, indicating the reduced toxicity.