Effect of Ozonation on Biodegradability Characteristics of Surplus Activated Sludge

The study investigates the effect of sludge ozonation on solid matter species, disintegration properties, sludge components, and solubilization characteristics under different operating conditions. Ozonation of surplus activated sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant indicates that soluble nitrogen, phosphorus and COD concentrations proliferate as a consequence of extending the ozone feeding time. A steady increase both in soluble nitrogen concentration and ratio of organic phosphorus to soluble phosphorus is observed through ozonation where specific ozone doses range between 4 and 11 mg O₃/g SS. Combined treatment of chemical oxidation and aerobic biodegradation to surplus activated sludge is also applied to improve the biodegradability of organic matter by partial chemical oxidative pretreatment with as little specific ozone consumption as possible. The partial oxidation by integrated ozonation is operated as a pre-oxidation step for the subsequent biological degradation, due to the fact that the competition with biological degradation in removing biodegradable organic compounds is avoided and most probably a more biodegradable sludge composition is obtained by means of ozonation. Combined treatment of chemical oxidation and aerobic biodegradation conducted to scrutinize the synergic effect of the coupled treatment system reveals that TS and COD removal efficiencies of ozonated sludge samples cannot be improved beyond the third aerobic biodegradation step.     

Feasibility of Sludge Ozonation for Stabilization and Conditioning

A pilot-scale sludge treatment plant was built to investigate the feasibility of ozonation processes for waste activated sludge treatment. Ozonation of wastewater sludge resulted in mass reduction by mineralization as well as by supernatant and filtrate recycle. Another advantage of sludge ozonation is a significant improvement of settleability and dewaterability. Experimental results showed that mass reduction of 70% and volume reduction of 85% compared with the control sludge was achieved through the sludge ozonation at a dose of 0.5?gO₃/gDS. It is also interesting to note that the filterability deteriorates up to ozone dose of 0.2?gO₃/gDS and then improves considerably at a higher ozone dose. The filterability could be improved by chemical conditioning even at a low ozone dose. The economic feasibility by cost analysis reveals that ozonation processes can be more economical than other alternative processes for sludge treatment and disposal at small-sized wastewater treatment plants.     

Incidence of an Ozonation Stage on the Treatment of Cherry Stillage by Activated Sludge

This article presents a laboratory study of the ozonation of diluted cherry stillage, a high-strength wastewater. Influence of variables, kinetics, and the effects of an ozonation stage coupled with the biological treatment by activated sludge are addressed. Single activated sludge processing was shown effective to remove biological oxygen demand (BOD) and chemical oxygen demand (COD) but polyphenols were reduced to a lesser extent. On the other hand, direct wastewater ozonation did not reduce COD and total organic carbon (TOC) appreciably, and foaming problems were experienced when a high gas flow rate was applied. However, polyphenols and UV₂₅₄ absorbance decreased substantially by means of ozonation. To best achieve complete cherry stillage purification, two ways of coupling ozonation with activated sludge are proposed. Ozonation prior to activated sludge is advised for high-concentration wastewater to reduce polyphenol concentration, thus removing inhibiting effects. For wastewater with low polyphenol concentration the sequence activated sludge–ozonation–activated sludge is preferred to enhance the overall process performance in terms of oxidation efficiency and sludge settling.     

Sludge Ozonation and its Application to a New Advanced Wastewater Treatment Process with Sludge Disintegration

The applicability of sludge ozonation on wastewater treatment processes was investigated to reduce the amount of excess sludge without losing phosphorus removal efficiency. Solubilization degree per ozone consumption for general sludge was in the range from 2.4 to 5.8 gSS/O₃ and from 4.1 to 7.7 gCOD/gO₃. Around 80 to 90% of solubilized organics was biodegradable at a solubilization degree of 0.3. Based on the experimental results, a lab-scale plant with sludge ozonation and phosphorus crystallization was constructed to investigate the treatment performance. Amount of excess sludge was reduced by 93% with almost complete removal of soluble BOD and phosphorus removal efficiency of more than 80%. The percentage of the effluent COD_Cr discharge increased from 10% to 14–17% after installing ozonation and crystallization because of the formation of non-biodegradable organic substances in ozonation process. Energy consumption of the innovative advanced process is comparable or can be even smaller than that of the conventional anaerobic/oxic (A/O) process in spite of the installation of ozonation and crystallization.     

Systematic Analysis of the Biochemical Characteristics of Activated Sludge During Ozonation for Lowering of Biomass Production

Properties of activated sludge during ozonation were analyzed. The structure and surface characteristics altered with the increase of ozone dosage. At low ozone dosage, the floc structure was completely dismantled. Floc fragments reformed through reflocculation at an ozone dosage greater than 0.20 g O₃·g^?1 mixed liquor suspended solids (MLSS). Inactivation of microorganisms in the activated sludge mixture was caused by ozonation. Microbial growth decreased by up to 65% compared to the control. Simultaneously, 92.5% of nucleotide and 97.4% of protein in microbial cells of the sludge were released. Organic substance, nitrogen and phosphorus were released from the sludge during the ozonation process. The initial value of soluble chemical oxygen demand (SCOD) was 72 mg·L^?1. When the ozone dosage was 0.12 g O₃·g^?1 MLSS, the value of SCOD rapidly reached 925 mg·L^?1, increased by almost 12-fold. Simultaneously, 54.7% of MLSS was reduced. The composition of MLSS was changed, indicating that the inner water of cells and volatile organic substance decreased during the ozonation process.     

Ozonation of Continuous-Flow Activated Sludge for Reduction of Waste Solids

The ultimate disposal of wastewater sludge has been, and continues to be, one of the most expensive problems faced by wastewater utilities in the United States. The objective of this research was to apply cell lysis and cryptic growth principles to activated sludge to study the applicability of ozonation to reduce the mass of secondary sludge. The study produced data and details for application of ozone to reduce secondary sludge production. The application of ozone reduced the mass of waste sludge by 30 to 50% depending on the ozonation rate and period.     

Domestic and Industrial Wastewater Treatment with Ozonated Activated Sludge

Poor sludge settleability is a problem encountered in many activated sludge wastewater treatment plants. This study was aimed at combatting the unwanted biological growths at the root of this phenomenon with ozone. Ozone dosed directly into the aeration basins of small activated sludge pilot plants treating both domestic and synthetic fuel wastewaters led to a substantial reduction of the bulking problem even at dosages as low as 6 to 10 mg/L. Ozone did not interfere in the delicate nutrient removal processes and significantly enhanced effluent quality.     

Ozonation within an Activated Sludge System for Azo Dye Removal by Partial Oxidation and Biodegradation

Pre-ozonation is often uneconomical for typical wastewaters with varied mixtures of organic compounds as more biodegradables than non-biodegradables are oxidized, all requiring ozone. The concept developed in this paper is ozonation within an activated sludge system to oxidize recalcitrant substances to more degradable forms and byproducts and to immediately assimilate or biodegrade these within the biological system. The focus was on a novel method of combining ozonation and biological treatment in one integrated unit without adversely affecting the bacterial population responsible for the biological degradation. An azo dye, spiked into the wastewater feed was used to study removal of a recalcitrant compound in a biological system.     

Reduction of Excess Sludge Produced by Biological Treatment Processes: Effect of Ozonation on Biomass and on Sludge∗

The excess sludge produced during biological treatment of wastewater can be reduced by treating this sludge with ozone in a specific reactor and recycling it to the biological facility. This increases the biodegradability of the inert fractions of the sludge without deteriorating the activity of the microorganisms. Ozone reacts only within the film zone near the gas/liquid interface: it is assumed that the size of the microflocs of active microorganisms is greater than the effective thickness of the film, thus protecting them from ozone. This coupled treatment produces treated water having satisfactory characteristics and a residual excess sludge that has an extremely high settling capability.     

Biogas Production of Ozone and/or Microwave-Pretreated Canned Maize Production Sludge

The production of canned maize is accompanied by formation of large volumes of waste water, with high contents of starch, and high chemical- and biochemical oxygen demand. In our work the effects of acidic, microwave and ozone pretreatment on the biogas production and aerobic biodegradability of canned maize production sludge were examined and the energy balance of the processes were determined when different sludge pretreatments were used. It was found that ozone treatment decreased the chemical oxygen demand, while the biochemical oxygen demand and the aerobic biodegradability increased. The combination of microwave and ozone treatment increased the biodegradability relative to ozone treatment alone.     

Ozonation of Primary Sludge and Digested Sludge to Increase Methane Production in a Chemically Enhanced Primary Treatment Facility

The purpose of this research was the investigation of the ozonation of sludge as a method to improve anaerobic digestion performance in a chemically enhanced primary treatment facility. Batch tests were conducted to evaluate the effect of ozonation on the physicochemical characteristics of both primary and digested sludge. Then, the performance of semi-continuous anaerobic digesters in combination with ozone treatment was investigated (pre-ozonation and post-ozonation). Ozonation of primary sludge did not increase the soluble COD nor the biodegradable COD, but resulted in the mineralization of a fraction of the organic matter into CO₂. However, the ozonation of anaerobic digested sludge resulted in an increase in soluble COD and biodegradable COD and in a small level of mineralization at the dose of 90 mg O₃/g COD. Pre-ozonation of primary sludge was not effective in enhancing the performance of the anaerobic digester. The coupling of ozonation and anaerobic digestion by means of the post-ozonation of digested sludge was found to be effective in improving methane production (+16%), for COD removal efficiency and for the dewaterability of anaerobic digesters compared to the control digester.     

Toxicity and Biodegradability Behavior of Xenobiotic Chemicals Before and After Ozonation: A Case Study with Commercial Textile Tannins

Ozonation of a natural tannin (NT; COD_o?=?1195 mg/L; TOC_o?=?342 mg/L; BOD_5,o?=?86 mg/L) and a synthetic tannin ST; COD_o?=?465 mg/L; TOC_o?=?55 mg/L; BOD_5,o?=?6 mg/L) being frequently applied in the polyamide dyeing process was investigated. Synthetic wastewater samples containing these tannins individually were prepared and subjected to ozonation at varying ozone doses (625– 1250 mgO₃/L wastewater), at pH?=?3.5 (the application pH of tannins) and pH?=?7.0 at an ozone dose of 1125 mgO₃/L wastewater. The collective environmental parameters COD, TOC, BOD₅, UV₂₅₄ and UV₂₈₀ (UV absorbance at 254 nm and 280 nm, representing aromatic and unsaturated moieties, respectively) were followed during ozonation. Changes in the biodegradability of the tannins were evaluated in terms of BOD₅ measurements conducted before and after ozonation. In addition, activated sludge inhibition tests employing heterotrophic biomass were run to elucidate the inhibitory effect of raw and ozonated textile tannins towards activated sludge biomass. Partial oxidation (45% COD removal at an ozone dose of 750 mg O₃/L wastewater and pH?=?3.5) of ST was sufficient to achieve elimination of its inhibitory effect towards heterotrophic biomass and acceptable biodegradability improvement, whereas the inhibitory effect and biodegradability of NT could not be reduced via ozonation under the same reaction conditions.     

Improving the Biodegradation of Organic Pollutants with Ozonation during Biological Wastewater Treatment

Pre-ozonation is often used to enhance the biodegradability of recalcitrant compounds prior to biological treatment of wastewater. A usual shortcoming of such an approach is wasting ozone on other compounds that are already biodegradable. This research followed a groundbreaking approach of degrading a recalcitrant substance with ozone during biological treatment. Two parallel bench-top activated sludge processes were fed a synthetic wastewater containing typical biodegradable substances and also methylene blue at 5 mg/L. Ozone was applied continuously and directly into one of the activated sludge units at 17 mg/L based on inflow rate. The methylene blue was removed by 95%?in the ozonated process compared with just 40%?removal in the non-ozonated control. The removal in the activated sludge without ozonation was demonstrated to be mainly due to biosorption. The ozone oxidation reaction by-products were analyzed using GC-MS on volatile substances collected in the headspace above ozonated samples of methylene blue and most found to be biodegradable. These by-products are expected to be degraded and assimilated in the same process unit together with the other biodegradables in the feed stream by the activated sludge process. The reaction rate with organic substances depleted the dissolved ozone at such a rate that the inactivation of the treatment bacteria (and protozoa) was minimal, mostly affecting the filamentous bacteria. A concern that ozone, as a powerful disinfectant, could inhibit or kill the beneficial bacteria in the activated sludge process was proven to be incorrect.     

活性炭催化剂臭氧催化氧化处理废水的研究进展

介绍了近年来国内外活性炭催化剂臭氧催化氧化的研究结果,对活性炭及金属负载型活性炭催化剂的反应机理进行了总结。讨论了非均相臭氧催化氧化过程中活性炭的主要作用,活性炭催化剂的表面物化性质、pH值、温度在臭氧催化氧化过程中的影响规律。并提出活性炭催化剂的降解机理以及催化剂性质与有机污染物的化学结构之间的关系还需要进一步的研究。     

Ozonation of Two Commercially Important Biocidal Finishing Agents

Ozonation of 2 commercially important textile biocidal finishing agents (called BI and BII herein) in aqueous solution was studied in a semi-batch bubble column reactor at different ozone feed rates (500, 750, and 900 mg/h) and pH (pH=7 and 12). Ozonation efficiency and kinetics were assessed in terms of COD, TOC and UV absorbance at 280 nm (UV₂₈₀) and 254 nm (UV₂₅₄), representing the aromaticity and unsaturated moieties of the studied textile biocides, respectively. Due to its chlorinated aromatic content, the fate of Adsorbable Organic Halogens (AOX) of BI was also followed during the ozonation experiments. At alkaline pH, appreciably higher COD and TOC removals were achieved, speaking for a free radical (^?OH) dominated degradation pathway for both tested biocides. AOX, UV₂₈₀ and TOC abatement rates obtained for BI ozonation at optimized reaction conditions indicated that the degradation of BI followed a sequential path of dechlorination, dearomatization, oxidation and mineralization, respectively.     

Oxone Enhanced Biological Activated Carbon in Denver,Colorado: A Pilot Plant Study

Five parallel ozone and activated carbon systems were compared for their effectiveness in treating unchlorinated effluent from the Denver Metropolitan Sewage Disposal District No. 1 wastewater facility. Data were gathered over four months of continuous operation. The objective of the study was to assess the potential for enhanced carbon column performance through the use of ozone.     

Effect of Ozonation on Degradation of Organochlorine Compounds in Biosludge of Pulp and Paper Industry

The waste-activated sludge in the pulp and paper industry has been classified as hazardous waste due to the presence of organochlorine compounds. The fate of organochlorine compounds during ozonation of biosludge as well as subsequent treatment in activated sludge process has been studied. Ozonation of biosludge at 45.3 ± 2.1 mg O₃/g dry solid dosage resulted in 23 ± 2 and 26 ± 4% removal of adsorbable organic halides and extractable organic halides compounds, respectively. Out of 12 chlorophenolic compounds identified by USEPA for regulation, 10 compounds were detected in the biosludge and 19–68% removal of the individual compounds was observed during ozonation. High molecular weight chlorinated compounds were decomposed to low molecular weight ones with partial dechlorination. The ozonation followed by biological treatment can remove more than 80% of organochlorine compounds.     

Combined Ozone Pretreatment and Anaerobic Digestion for the Reduction of Biological Sludge Production in Wastewater Treatment

The ever-increasing amount of solid waste generated by wastewater treatment plants highlights emerging economic and environmental issues. In order to develop new processes producing less sludge, the use of ozone combined with anaerobic digestion was investigated for waste activated sludge treatment. This paper was aimed at evaluating the impact of ozone pretreatment on anaerobic digestion and particularly the enhancement of biogas production. Sludge solubilization was estimated in terms of modification of chemical oxygen demand, solids and nitrogen. Batch anaerobic digestion highlighted the enhancement of ozonated sludge biodegradability. Ozonation led to an increase in biogas production. The ozone dose of 0.15 g O₃/g total solids resulted in a considerable increase in the soluble COD ratio from 4% to 37%. This ozone dose achieved the highest increase in biogas production: 2.4 times greater than without chemical pretreatment.     

Understanding the Effects of Ozonation on a Combined Municipal/Industrial Secondary Effluent

An increase in the biodegradability of secondary effluent after ozonation as measured by CBOD₅ (carbonaceous BOD₅), generally has been considered to be due to the conversion of non-biodegradable organic material. Experiments on a specific combined unicipal/industrial waste containing a high percentage of malting plant wastewater showed that an increase in CBOD5 realized at the waste treatment plant was due to a shift in the oxygen uptake curve. Ozonation was found to affect both non-biode-gradable and biodegradable organic matter and resulted in improved overall effluent quality despite the observed increase in CBOD₅. As an indication of effluent quality, the CBOD₅ test is felt to be inadequate.     

Effect of Catalytic Ozonation Coupling with Activated Carbon Adsorption on Organic Compounds Removal Treating RO Concentrate from Coal Gasification Wastewater

This paper reports a novel system of catalytic ozonation coupling with activated carbon adsorption for removing the organic compounds treating in the RO concentrate from coal gasification wastewater. The effect of ozone dosage, catalyst dosage, reaction time, influence pH, and temperature on organic compounds removal were examined for the processes. In the catalytic ozonation process, increasing solution pH, dosages ozone, and catalyst were statistically significant for improving the performance. In addition, the high salinity with chloride concentration of 15 g/L could reduce the catalyst specific surface area by 18%. Thus, high salinity showed negative influence on the catalytic effect in TOC removal. Regarding activated carbon adsorption process, modified activated carbon by NaOH revealed advantages in adsorbing organic compounds treating catalytic ozonation effluent. With the ozone dosage of 120 mg/L, catalyst dosage of 2.0 g/L, catalytic ozonation reaction time of 1 h, and modified activated carbon adsorption time of 1 h, the average TOC removal efficiencies were maintained at the stable level of 58% with the TOC concentration of 26 mg/L.