Ozonation strategies to reduce sludge production of a seafood industry WWTP

In this work, several alternatives related to the application of ozone in different streams of a seafood industry WWTP were evaluated to minimize the production of waste sludge. The WWTP was composed of two coagulation-flocculation units and a biological unit and generated around of 6550 kg/d of sludge. Ozone was applied to sludge coming from flotation units (110 g TSS/L) at doses up to 0.03 g O(3)/g TSS during batch tests, no solids solubilization being observed. Ozone doses ranging from 0.007 to 0.02 g O(3)/g TSS were also applied to the raw wastewater in a bubble column reaching a 6.8% of TSS removal for the highest ozone dose. Finally, the effect of the pre-ozonation (0.05 g O(3)/g TSS) of wastewater coming from the first flotation unit was tested in two activated sludge systems during 70 days. Ozonation caused a reduction of the observed yield coefficient of biomass from 0.14 to 0.07g TSS/g COD(Tremoved) and a slight improvement of COD removal efficiencies. On the basis of the capacity for ozone production available in the industry, a maximum reduction of sludge generated by the WWTP of 7.5% could be expected.     

Ultrasonic treatment of biological sludge: Floc disintegration, cell lysis and inactivation

The aim of this work was to study the effect of ultra sound treatment on the solid content of sludge and biological activity, and the increase in the soluble chemical oxygen demand (SCOD), proteins and nucleic acids concentrations during sonication. The results showed that sonication effectively degraded and inactivated the sludge. The sludge disintegration and cell lysis occurred continuously while sludge inactivation mainly occurred in the second stage (10-30 min) during sonication. The SCOD, supernatant proteins and nucleic acids concentrations, and sludge mass reduction and inactivation degrees increased with the sonication time and power density increases. Higher energy ultrasound was more efficient than lower energy ultrasound for the sludge treatment.     

Biochemical modifications induced in human blood by oxygenation-ozonation

Some biochemical effects determined on human blood after addition of a gas mixture composed of oxygen (approximately 96%) and ozone (approximately 4%) have been evaluated. Ozone was used in a mild concentration ranging between 0.21 and 1.68 mM. Within few minutes after rapid mixing of the equal gas-liquid volumes, the ozone was consumed because by instantaneously reacting with biomolecules, generating reactive oxygen species (particularly hydrogen peroxide) having very short lifetime and lipid oxidation products. The following results are oxygen-ozone dose dependent: (1) The pO(2) values have risen from about 40 up to 400 mmHg. (2) By testing the highest ozone concentration, the total antioxidant capacity of blood decreased within 1 min from 1.35 to 0.91 mM but regained its normal values within 20 min owing to the rapid reduction of oxidized antioxidants operated by erythrocytes. (3) Similarly, intraerythrocytic reduced glutathione after ozonation decreased from the initial value of 5.71 to 4.56 micromol/g Hb. (4) Both hemolysis and methemoglobin showed a negligible increase.     

Decreased levels of ascorbic acid in lung following exposure to ozone

Mice were exposed to concentrations of 20, 40 and 200 ppm ozone in air for 30 min. Ozone exposure decreased lung ascorbic acid levels and increased lung weight by up to 50% in a dose related manner. On incubation in Krebsphosphate solution, lung slices from mice exposed to 200 ppm ozone released a smaller fraction of their content of ascorbic acid into the medium than did lung slices from control mice, suggesting that there was a preferential loss of extracellular ascorbic acid during ozone exposure. These results are consistent with the proposed function of ascorbic acid as an extracellular antioxidant in lungs.     

Bioremediation of phenolic compounds having endocrine-disrupting activity using ozone oxidation and activated sludge treatment

The bioremediation of water system contaminated with phenolic compounds having endocrine-disrupting activity,i.e. 2,4-dichlorophenol, 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T), was investigated by using ozone oxidation and activated sludge treatment. Ozone oxidation (ozonation time: 30 min) followed by activated sludge treatment (incubation time: 5 days) was an efficient treatment method for the conversion of phenolic compounds in water into carbon dioxide and decreased the value of total organic carbon (TOC) up to about 10% of initial value. Furthermore, 2,4-D was dissolved in water containing salt,i.e. artificial seawater (ASW), and this water was used as model coastal water contaminated with phenolic compounds. The activated sludge treatment (incubation time: 5 days) could consume significantly organic acids produced from 2,4-D in the model costal water by the ozone oxidation (ozonation time: 30 min) and decrease the value of TOC up to about 35% of initial value.     

Depletion of urate in human nasal lavage following in vitro ozone exposure

Ozone, a strong oxidant present in summer smog, is thought to primarily react with antioxidant molecules found in the epithelial lining fluid of the respiratory tract. In humans, as much as 40% of inhaled ozone can be removed in the nasal cavity where the major extracellular antioxidant has been identified as uric acid. The present study was undertaken to examine urate/oxidant interactions in human nasal lavage fluid following in vitro exposure to ozone at concentrations relevant to the U.K. Lavage fluid was collected from 8 volunteers using a modified Foley catheter which permits prolonged contact of isotonic saline with the anterior nasal cavity. Nasal lavage samples in multiwell plates were exposed to ozone at concentrations of 50, 100 and 250 ppb. Samples were removed at intervals from 15 to 240 min following exposure and assayed for uric acid depletion. Uric acid concentrations in the nasal lavage were found to fall from 8.52 (time zero) to 3.99 μM, 0.05 and 0.07 μM after 240 min at 50, 100 and 250 ppb ozone respectively. At a non-environmentally relevant ozone concentration of 1000 ppb, uric acid was completely depleted after 60 min. Regression analysis showed a linear correlation between rate of loss of urate and ozone concentration (R² = 0.97). A novel, non-invasive technique is described to investigate antioxidant compromise and its importance in individual subjects. We conclude that uric acid in nasal lavage samples is scavenged by ozone in a dose and time dependant manner.     

Effects and model of alkaline waste activated sludge treatment

Due to lack of information about alkaline sludge treatment with high dose at ambient temperature, alkaline sludge treatment was investigated to know the effects of different doses (0-0.5 mol/L) of sodium hydroxide (NaOH) and calcium hydroxide [Ca(OH)2] at 0-40 degrees C. Results showed that NaOH was more suitable than Ca(OH)2 for sludge disintegration. For NaOH treatment, most efficient dose was about 0.05 mol/L (0.16 g/g dry solid), and 60-71% solubilization of organic matters was achieved in first 30 min during its treatment of 24h. The process is described by a transmutative power function model, and relation between reaction rate constant and temperature are according with Arrhenius equation. Low dose NaOH treatment (<0.2 mol/L) deteriorated sludge dewatering ability obviously, while the ability was recovered gradually with the increase of NaOH dose. For Ca(OH)2 treatment, the disintegrated floc fragments and soluble organic polymers can be re-flocculated with the help of calcium cations. Consequently sludge disintegration effect was counteracted and dewatering ability improved.     

Effects of ozone treatment on cell growth and ultrastructural changes in bacteria

Ozone appeared to inhibit growth and caused the death of gram negative and gram positive tested bacteria: Escherichia coli, Salmonella sp., Staphylococcus aureus and Bacillus subtilis. Bacterial cultures at 10(3), 10(4), 10(5), 10(6), and 10(7) cfu/ml dilution were exposed to 0.167/mg/min/L of ozone at different time intervals (0, 5, 10, 15, 30, 60, 90, 120, and 150 min). Cell viability was observed in all types of tested bacteria at 10(3), 10(4), 10(3) cfu/ml within 30 min after ozone exposure. However, cell inactivation was not significantly observed at concentrations of 10(6), 10(7) cfu/ml even after an exposure of 150 min. Ultrastructural changes of treated bacteria showed deformation, rough damage and surface destruction revealed by scanning electron microscopy. Some bacterial cells showed collapsed and shrunken patterns within 60 min and severe rupture and cellular lysis after 90 min of ozone treatment. This study supports the proposed mechanism of the bacteria inactivation by ozone that caused cell membrane destruction and finally lysis reaction. Thus, the precaution of using ozone as a biocide should be used to address appropriate concentrations of bacterial contamination in water.     

Soil-plant-water aspects of ozone phytotoxicity in tomato plants

Summary Tomato (Lycopersicon esculentum Mill.) plants were grown in controlled environments and subjected to different soil water regimes. At 3-, 5-, and 7-leaf growth stages, plants were fumigated with ozone at 50 or 100 pphm for 1 h. Plants at 5- or 7-leaf stage were not as sensitive to ozone as were the young plants fumigated at 3-leaf stage. At the 7-leaf stage, leaf injury at nearoptimum water condition was very minimal, even at ozone concentration of 100 pphm. Ozone treatment decreased total dry matter of optimally watered plants fumigated at the 3-leaf stage. Plants subjected to water stress resulting in low leaf relative turgidity prior to ozone fumigation, were considerably protected from ozone phytotoxicity. Open stomata were an important factor in ozone phytotoxicity. Post-fumigation water regimes had no effect on eventual leaf injury. re]19720627     

Decline in microbial activity does not necessarily indicate an end to biodegradation in MSW-biowaste: a case study

The aim of this study was to examine whether a decline in microbial activity (i.e., CO(2) output) during the biodegradation of municipal solid waste (MSW) indicated an end to biodegradation and the appearance of a stable, final product. As the organic fraction of MSW was biodegraded in an 8 clamp Cambridge Batch System composter, CO(2) output declined by 50% and moisture content at the end of the process was <20%. Levels of biodegradable material remaining in the product were determined by the dynamic respiration index (DRI) method but despite 151 days in the composting system biodegradable material was still present at levels (24130mgO(2)/kgdry matter (DM)) which exceeded draft EU biowaste directive (2001) guidelines (10,000mgO(2)/kgDM). Further laboratory based incubations demonstrated that microbial activity and hence biodegradation of organic material could be restarted if moisture levels were adjusted suggesting that dehydration limited microbial activity. Low levels of microbial activity alone did not therefore indicate and end to biodegradation, biodegradable material was not exhausted and the final product was not stable which has serious implications for its end-use.     

Ozone gas affects physical and chemical properties of wheat (Triticum aestivum L.) starch

In this experiment, bread wheat flour and isolated wheat starch were treated with ozone gas (1,500 mg/kg at 2.5 L/min) for 45 min and 30 min, respectively. Starch was isolated from treated flour. Ozone treated starch and starch isolated from ozone treated flour had similar chemical and physical properties. Chemical analysis of starch isolates indicated depolymerization of high molecular weight amylopectins; with a subsequent increase in low molecular weight starch polymers as a result of starch hydrolysis. Ozone treatment resulted in elevated levels of carboxylic groups and decreased total carbohydrate content in amylopectin fractions. ¹H NMR results indicated formation of a keto group [(1→4)-3 keto] at the H-2 terminal (proton at C-2 position) and β-glucuronic acid at the H-1 terminal (proton at C-1 position). DSC transition temperatures and change in enthalpy were not affected by ozone treatment. Increased swelling power and RVA breakdown were observed in starch from ozone treated samples.     

Changes in composition and microbial communities in excess sludge after heat-alkaline treatment and acclimation

This study examined the effects of combining heat-alkaline treatment (HAT) with an acclimation process on sludge reduction. Changes in sludge components and microbial communities in both the mixed liquor suspended solids (MLSS) and supernatant fractions were monitored throughout the process. HAT was performed under different pH conditions (pH 7, pH 11 and pH 13) at 60 °C. Approximately 42–62% of the released materials were proteins. After an 8-day acclimation of sludge, the protein concentration in the supernatant had significantly decreased under all conditions. Treatment conditions at pH 11 were optimal for sludge reduction due to the increased efficiency and reduced consumption of chemicals to adjust the pH. A molecular analysis showed that the microbial consortia in both fractions after the cell lysis differed depending on the pH and temperature, and only a few types of bacteria were resistant under extreme conditions. The microbial communities in the MLSS under different conditions were similar after the 8-day acclimation.     

Characterization of Gaseous Ozone Decomposition in Soil

Laboratory scale batch experiments were performed to investigate the decomposition characteristics of gaseous ozone in porous media. The decomposition rates of gaseous ozone in several solid media were determined, and the relationship of moisture content with sorbed ozone molecules was evaluated. Ozone decomposition in control and glass beads packed columns followed second-order reaction kinetics, while ozone consumption in a sand-packed column demonstrated first-order kinetics with a rate constant of 0.0109 min^?1 and half-life of 1.0 h. The presence of typical metal oxides in the soil resulted in ozone consumption rates in the following order: hematite (Fe₂O₃) > silica-alumina (SiO₂Al₂O₃) > alumina (Al₂O₃) > silica (SiO₂). Ozone decomposition was highly dependent upon soil moisture content. Over 90% of the total ozone mass decomposed in the field soil with moisture content at less than 1 wt%, whereas as low as 5–15% of the total ozone mass degraded with moisture content at more than 2 wt%. In conclusion, ozone decomposition in soils was primarily controlled not only by soil organic matter but also by reactive metal oxides on the soil surface. These two factors were shown to be highly dependent upon soil moisture content.     

Reduction of Root-Knot Nematode, Meloidogyne javanica, and Ozone Mass Transfer in Soil Treated with Ozone

Ozone gas (O(3)) is a reactive oxidizing agent with biocidal properties. Because of the current phasing out of methyl bromide, investigations on the use of ozone gas as a soil-fumigant were conducted. Ozone gas was produced at a concentration of 1% in air by a conventional electrical discharge O(3) generator. Two O(3) dosages and three gas flow rates were tested on a sandy loam soil collected from a tomato field that had a resident population of root knot nematodes, Meloidogyne javanica. At dosages equivalent to 50 and 250 kg of O(3)/ha, M. javanica were reduced by 24% and 68%, and free-living nematodes by 19% and 52%, respectively. The reduction for both M. javanica and free-living nematodes was dosage dependent and flow rate independent. The rates of O(3) mass transfer (OMT) through three soils of different texture were greater at low and high moisture levels than at intermediate ones. At any one soil moisture level, the OMT rate varied with soil texture and soil organic matter content. Results suggest that soil texture, moisture, and organic matter content should be considered in determining O(3) dosage needed for effective nematode control.     

Experiences with the dual digestion of municipal sewage sludge

The dual digestion process was investigated using sludge samples collected at the WWTP of Tomaszow Mazowiecki (Poland). Mixed sludge was treated in a laboratory setup under batch and semi-continuous conditions. Dual digestion with a 1d SRT aerobic thermophilic pretreatment followed by an anaerobic step with 20 d of SRT turned out to be optimal, since a 44-46% VS reduction and a biogas yield of 480 dm(3)/kg VS fed were achieved. In the course of the process, the concentration of nitrogen in supernatant increased over 5 times and its major portion was converted into ammonia. Phosphorus also entered the supernatant, reaching over 200 g/m(3). The dual digestion noticeably deteriorated the sludge dewaterability. Following completion of the process, capillary suction time measurements averaged 64 s for the raw sludge, 400 s for aerobically pretreated sludge and 310-360 for the anaerobically digested sludge. Aerobic pretreatment consistently reduced Enterobacteriaceae content to below detectable limits.     

The effect of exercise on nasal uptake of ozone in healthy human adults.

The nose may help protect the lower respiratory tract from the effects of ambient ozone by scrubbing ozone from inspired air. Reductions in both nasal resistance and nitric oxide production with exercise may influence the efficiency of ozone uptake in the nose. Nasal ozone uptake was measured in 10 healthy volunteers before and after 15 min of moderate bicycle exercise. Ozone (0.2 parts/million) was pulled through both nostrils and out of the mouth at a constant flow while the subjects closed their epiglottises. Nasal uptake of ozone was determined by comparing the ozone concentration entering the nostrils to that exiting the mouth. Average preexercise uptake of ozone was 56 +/- 7.8 and 37 +/- 4.9% at 10 and 20 l/min, respectively. These averages did not significantly differ from those immediately postexercise (55 and 37%). Nasal ozone uptake increased significantly (P < 0.001) with decreasing flow rate, but intersubject variability in uptake could not be predicted by nasal volume or cross-sectional areas (as measured by acoustic rhinometry) or endogenous nitric oxide production. However, the percent change in ozone uptake after exercise, within an individual, was correlated with both 1) percent change in nasal volume (r = 0.70 at 10 l/min) and 2) percent change in the rate of volumetric expansion between the nasal valve and turbinates (r = 0.82 at 10 l/min). These results may be useful for assessing human risk associated with ozone exposure during exercise.     

Responses to ozone in 12 provenances of European beech (Fagus sylvatica): genotypic variation and chamber effects on photosynthesis and dry-matter partitioning

Seedlings of 12 provenances of European beech ( Fagus sylvatica ) were exposed to ambient, non-filtered air (NF) or NF+50 nl l⁻¹ ozone (NF50) for 8 h d⁻¹ in open-top chambers (OTCs), from 1 June to 4 October 1995. In 1996 exposure was continued from 31 May to 1 October at four levels: charcoal-filtered air (CF), NF, NF50 and NF+100 nl l⁻¹ ozone (NF100). Provenances were grown for both seasons in outside reference plots. All treatments were replicated. Ozone did not affect gas exchange in the provenances until late in the second season. NF100 reduced photosynthesis by 18% in August 1996 compared to CF. In September, photosynthesis was reduced by 22% in NF50 and by 29% in NF100. After two seasons, ozone reduced the root:shoot ratio by 24% when comparing CF and NF100; this was caused by reductions in the root biomass. Ozone did not affect height growth or stem diameter, and there were no ozone×provenance interactions for any growth parameter. There was, however, a significant ozone×provenance interaction for photosynthesis, showing northwest European provenances to be more sensitive to ozone than southeast European provenances when comparing dose–response estimates. This is interpreted in terms of genetic adaptation of the photosynthetic apparatus to regional growing conditions. Seedlings in the chambers grew 45% taller, and had 28% more shoot biomass and 29% smaller root biomass, resulting in a 44% reduction of root:shoot ratios compared to seedlings outside. Increased temperature and decreased PAR inside the chambers relative to the outside were probably the main causes for the differences. The magnitude of the chamber effects in OTCs raises doubts about conclusions drawn from ozone exposures in such chambers. This and previous ozone experiments with OTCs may have reached inaccurate conclusions concerning the size of ozone responses due to chamber effects.     

Ozone-induced inactivation of antioxidant enzymes

Ozone is an air pollutant that damages a variety of biomolecules. We investigated ozone-induced inactivation of three major antioxidant enzymes. Cu/Zn superoxide dismutase was inactivated by ozone in a concentration-dependent manner. The concentration of ozone for 50% inactivation was approximately 45 microM when 10 microM Cu/Zn superoxide dismutase was incubated for 30 min in the presence of ozone. SDS-polyacrylamide gel electrophoresis (PAGE) showed that the enzyme was randomly fragmented. Both ascorbate and glutathione were very effective in protecting Cu/Zn superoxide dismutase from ozone-induced inactivation. The other two enzymes, catalase and glutathione peroxidase, were much more resistant to ozone than Cu/Zn superoxide dismutase. The ozone concentrations for 50% inactivation of 10 microM catalase and glutathione peroxidase were 500 and 240 microM, respectively. SDS-PAGE demonstrated that ozone caused formation of high molecular weight aggregates in catalase and dimerization in glutathione peroxidase. Glutathione protected catalase and glutathione peroxidase from ozone but the effective concentrations were much higher than that for Cu/Zn superoxide dismutase. Ascorbate was almost ineffective. The result suggests that, among the three antioxidant enzymes, Cu/Zn superoxide dismutase is a major target for ozone-induced inactivation and both glutathione and ascorbate are very effective in protecting the enzyme from ozone.     

Energy-efficient sludge sonication: power and sludge characteristics

This paper improves the energy efficiency for sludge treatment using ultrasound. The sludge organic content, solid concentration, ultrasonic intensity, and time were optimized. A new index, kWh/kgSCOD-increase, was used to evaluate the energy efficiency that covers both sludge characteristics and lysis effectiveness. The results showed that the energy efficiency of sludge sonication was in the range of 102-347kWh/kgSCOD-increase. Higher VS/TS ratio gave higher energy efficiency. Optimal solid concentration (TS) was found to be 20g/L; low TS (5.0g/L) consumed 137% more energy; while higher TS might assimilate the sound energy and decrease the efficiency. The cavitation threshold for sludge was 20-30W/cm(2), below which no sludge lysis was observed. The lowest effective sound intensity (31.4W/cm(2)) was best and saved 20-35% energy compared to higher intensities. The initial first minutes of sonication were most effective; hence intensive-short treatment was preferred.     

Ozonation of lysozyme in the presence of oleate in reverse micelles of sodium di-2-ethylhexylsulfosuccinate.

Ozone is shown to react with lysozyme in reverse micelles formed by 0.1 M sodium di-2-ethylhexylsulfosuccinate and 1.2-3 M water (pH 7.4) in isooctane solvent. The reaction of ozone is assessed by the oxidation of tryptophan residues in the protein to N-formylkynurenine. Cosolubilization of oleate in lysozyme-containing reverse micellar solutions at concentrations of 0.5-10 mM results in a progressive inhibition (19% to 82%) of the oxidation of tryptophan residues with a concentration for 50% inhibition around 2 mM. At this concentration of oleate, the magnitude of inhibition is independent of the micelle size and concentration, the overall interfacial area of reverse micelles, and the amount of ozone employed. These findings are discussed in terms of competitive reactions of ozone with unsaturated fatty acids and proteins in the lung lining fluid and in biological membranes.