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.     

Combination of Ozonation and the Fenton Processes for Landfill Leachate Treatment: Evaluation of Treatment Efficiency

Single processes such as ozonation, ozone/hydrogen peroxide, Fenton and several combined treatment schemes were applied for leachate collected from a waste disposal site. The implementation of combined Fenton and ozonation processes resulted in the highest chemical oxygen demand removal (77% from initial value) among all the treatment methods applied, while biodegradability improvement was observed during the Fenton pre-treatment only. Some decrease of chemical oxygen demand was obtained during the single ozonation or combined schemes including ozone resulting in slight if any biodegradability improvement. The addition of hydrogen peroxide to ozonation did not enhance chemical oxygen demand, dissolved organic carbon or biochemical oxygen demand removal compared to ozone alone. Ferric chloride coagulation used as a pre-treatment stage did not improve subsequent chemical oxygen demand removal by ozonation or the Fenton processes. Taking into account the effective chemical oxygen demand, dissolved organic carbon removal and biodegradability improvement the single Fenton process seems to be a preferable treatment method for the leachate treatment. Some reduction in toxicity to Daphnia magna was observed after the application of the studied treatment methods.     

臭氧氧化与序批式好氧活性污泥法组合工艺的污泥减量化效果

该文研究了臭氧技术应用于剩余污泥处理过程中臭氧利用率及污泥的可生化性随时间的变化,组建了臭氧氧化与序批式好氧活性污泥法结合的联合工艺。将臭氧单元处理过的污泥全部回流至曝气池与污水进行合并处理,考察了不同臭氧投加量下联合工艺中剩余污泥的产量和污水处理效果。结果表明,当处理污泥浓度为4 000 mg/L,污泥体积为3 L,臭氧进气浓度为6.5 mg/L,气量为6 L/min时,前20 min的臭氧利用率几乎为100%,随后利用率逐渐降低;污泥的可生化性先降低,而后逐渐升高,在30 min时达到最大,其后又开始下降;当臭氧投加量为0.078 kg O3/kg MLSS时,联合工艺的污泥增长率几乎为0,同时出水水质相对对照组没有明显变化。     

Combined ozone pretreatment and biological processes for removal of colored and biorefractory compounds in wastewater from molasses fermentation industries

BACKGROUND: The use of ozone combined with biological treatment was investigated for molasses fermentation wastewater containing highly concentrated, brown and biorefractory compounds. These persistent compounds, known as melanoidins, generate disposal issues: in the environment, the color is problematic for aquatic life; and in municipal wastewater treatment plants, the molecules are biorefractory. RESULTS: This paper aims to evaluate the impact of ozone pretreatment, applied in the range 0.1 to 1 g g^?1 consumed ozone doses, on both macroscopic physico‐chemical parameters such as chemical oxygen demand (COD), total organic carbon (TOC), color and UV absorbance, and batch aerobic biodegradability. Then, performances of ozone pretreatment are assessed in terms of biodegradability improvement in batch and semi‐continuous anaerobic processes and, also, in semi‐continuous denitrification as a potential carbon source. Ozonation applied at the ozone dose of 0.5 g O₃ g^?1 COD led to an increase in biodegradability in all bioreactors. On average, the pretreatment resulted in an increased biodegradable fraction from zero to 33% without noticeable toxicity on biomass. This ozone dose also achieved 45% nitrogen removal by biological denitrification. CONCLUSION: Ozone pretreatment is a suitable technique for the biodegradability improvement of molasses fermentation wastewater, in aerobic, anaerobic and anoxic conditions. The pretreatment should be optimized in order to maximize the subsequent biodegradability. Copyright © 2010 Society of Chemical Industry     

The Influence of Ozone,Oxygen and Chlorine on Biolocical Activity on Biological Activated Carbon

A laboratory study was conducted into the effects of the treatment of activated sludge effluent with different oxidants on the biodegradability of the organic substances. It was found that, under the experimental conditions described, ozone increased the biodegradability, whereas chlorine had no apparent significant effect. The effect of continuous oxidative pretreataent of activated sludge effluent on microbial populations and the biological activated carbon used subsequently in the process also was studied. It was found that ozone, particularly at a dosage of about 5 mg/L promoted biological activity, while chlorine and oxygen (in addition to the dissolved oxygen already in the effluent) had no significant effect on the biological population size.     

生物法处理维生素 C 生产污水工艺研究

利用生物法,采用微生物化、物理化学化、好氧生化组合工艺处理维生素 C 生产系统污水,针对此种污水量大、有机物含量高、可生化性差、盐度高,结合生产过程中固体废弃物有待利用等特点,有效的引入了铁碳床微电解和类芬顿反应,对各步主要影响因素进行了研究.     

Enhancement in mineralization of some natural refractory organic compounds by ozonation–aerobic biodegradation

Two schemes, the first involving ozonation followed by final aerobic biodegradation (phase I experiments), and the second involving initial aerobic biodegradation, followed by ozonation and subsequent final aerobic biodegradation (phase II experiments), were examined for enhanced mineralization of refractory model compounds, viz. gallic acid, tannin and lignin. In all cases, and irrespective of the applied scheme, chemical oxygen demand (COD), total organic carbon (TOC), COD/TOC ratio, and specific UV absorbance at 280 nm attributed to the model compounds decreased with application of increasing ozone dose. The residual organic matter remaining after ozonation exhibited enhanced aerobic biodegradability in all cases. Further, in all cases and irrespective of the applied scheme, the overall amount of COD and TOC removed through the combination of ozonation and biodegradation processes increased with increase in ozone dose for all three model compounds, and more than 90% COD removal could be achieved with an ozone dose of 3 mg ozone absorbed per mg initial TOC, as compared with approximately 40% COD removal when no ozone was applied. Treatment by the first scheme resulted in the fraction of starting COD removed through biodegradation decreasing with increase in ozone dose in all cases, while this fraction increased or remained constant during treatment using the second scheme. In the case of tannin and lignin, similar overall COD removal could be achieved at lower ozone doses using scheme II. Due to incorporation of the initial aerobic biodegradation step in scheme II, the ozone requirement for additional mineralization, ie mineralization over and above that achieved by aerobic biodegradation, was also lower than that in scheme I. Copyright © 2005 Society of Chemical Industry     

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.     

Effect of microwave irradiation on the disintegration and acidogenesis of municipal secondary sludge

This work experimentally determined the effect of microwave treatment on the disintegration and acidogenesis of municipal secondary sludge. Sludge samples (500 g) were heated for 0, 3, 5, 7, 9, 11, and 15 min in a microwave oven (2450 MHz, 700 W). The solubilization degree (soluble chemical oxygen demand (SCOD)/COD) of sludge increased asymptotically with microwave irradiation time from 2% at 0 min to 22% at 15 min. The concentrations of soluble protein, carbohydrate, lipid, and calcium also increased with microwave irradiation time. The biochemical acidogenic potentials (BAP) of sludge increased from 3.58 to 4.77 g COD l⁻¹. The results show that microwave irradiation increases the solubilization degree and BAP of municipal secondary sludge.     

Integration of continuous biological and chemical (ozone) treatment of domestic wastewater: 1. Biodegradation and post‐ozonation

The continuous treatment of domestic wastewater by an activated sludge process and by an integrated biological–chemical (ozone) oxidation process were studied in this work. Chemical oxygen demand (COD), biochemical oxygen demand (BOD), absorbance at 254 nm (UV₂₅₄) and nitrogenous compound content were the parameters followed in order to evaluate the performance of the two processes. Experimental data showed that both UV₂₅₄ and COD reductions are improved in the combined biological–chemical oxidation procedure. Thus, reductions of 59.1% and 37.2% corresponding to COD and UV₂₅₄, respectively were observed after the biological process (hydraulic retention time = 5 h; mixed liquor volatile suspended solids concentration = 3142 g m⁻³) compared with 71.0% and 78.4% obtained when a post‐ozonation step ( D _O3 = 41.7 g m⁻³) was included. During conventional activated sludge treatment, appropriate nitrification levels are only achieved with high hydraulic retention time and/or biomass concentration. Ozonation after the secondary treatment, however, allows improved nitrogen content reduction with total nitrite elimination. Post‐ozonation also leads to a higher biodegradability of the treated wastewater. Thus, the ultimate BOD/COD ratio goes from 0.16 after biological oxidation to 0.34 after post‐ozonation with 41.7 g O₃ m⁻³. © 1999 Society of Chemical Industry     

Activated sludge process coupled with intermittent ozonation for sludge yield reduction and effluent water quality control

BACKGROUND: Ozone is applied in wastewater treatment for effluent water quality improvement (post‐ozonation) as well as for excess sludge reduction (in the recirculation line). There is some evidence that ozone dosed directly to aerobic biooxidation (ABO) process enhances degradation of recalcitrant compounds into intermediates, following their biodegradation in the same reactor. However, no information regarding the influence of ozone on sludge yield in this system was found. Therefore, the current work aimed to evaluate the effect of ozone on the sludge yield when ozone is dosed directly to the ABO process. In addition, batch and continuous treatment schemes for phenolic wastewater treatment are compared. RESULTS: The results revealed that an optimal ozone dose of ～30 mgO₃ L^?1 day^?1 reduced the sludge yield by ～50%, while effluent water quality in terms of total chemical oxygen demand (TCOD), compared with a conventional ABO process, was improved by 35.5 ± 3.6%. Slight improvement in soluble COD removal at the same ozone dose was also detected. The toxicity of effluent water was reduced as the ozone dose was increased. CONCLUSIONS: In an integrated ozonation‐ABO process it is possible to simultaneously reduce sludge yield and to improve effluent water quality, as COD and toxicity are reduced. Copyright © 2011 Society of Chemical Industry     

Improvement of Biodegradability of Oil Field Drilling Wastewater Using Ozone

The possibility of improving the biodegradability of drilling wastewater using ozone was investigated following coagulation pretreatment. The biodegradability of wastewater was improved significantly following the start of ozonation, and the molecular weight of organic compounds decreased continuously with the progress of oxidation. It is interesting that minimum biochemical oxygen demand, total organic carbon (BOD/TOC) ratio (0.4 g/g) was observed when wastewater was treated with ozone continuously for 15 min. The combination of ozonation for 5 min (ozone consumption ratio of 2.6 g ozone/g TOC) followed by biological degradation produced a total TOC removal rate of 54.3%, which was comparable to direct ozonation for 30 min under the same conditions (TOC removal rate of 54.9%; ozone consumption ratio of 8.7 g ozone/g TOC). It is clear that biological treatment following short-term ozonation was very efficient in TOC removal. A process of successive coagulation-precipitation, ozone oxidation, and biodegradation seemed to be a good option for drilling wastewater treatment.     

Ultrasonic pre‐treatment of biological sludge: consequences for disintegration,anaerobic biodegradability,and filterability

BACKGROUND: Disintegration was developed as a pretreatment process for sludge to accelerate the digestion processes. Ultrasonic treatment may be a good alternative for sludge disintegration. In this study, different specific energy inputs ranged between 0 and 15 880 kJ kg^?1 and very low ultrasonic densities ranged between 0.04 and 0.1 W mL^?1 were applied to biological sludge for disintegration purposes. The potential for improving anaerobic digestion through ultrasonic pre‐treatment and the effect of ultrasonic pre‐treatment on the filterability characteristics of sludge were also investigated. RESULTS: 9690 kJ kg^?1 TS of supplied energy and very low power density of 0.09 Wm L^?1 are efficient for floc disintegration. For 9690 kJ kg^?1 TS, 44% higher methane production was achieved than with raw sludge as a result of biochemical methane potential assay. The supernatant characteristics of the sludge were also affected by the ultrasonic pre‐treatment. For 9690 kJ kg^?1 TS, the soluble chemical oxygen demand (SCOD), dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) in the sludge supernatant increased by 340%, 860%, 716%, and 207.5%, respectively. CONCLUSION: Ultrasonic pre‐treatment is an effective method for biological sludge disintegration even at very low ultrasonic density levels. It leads to increased anaerobic biodegradability but deteriorates the filterability characteristics of biological sludge. Copyright © 2009 Society of Chemical Industry     

Biodegradation of poly(butylene adipate‐co‐butylene terephthalate)/layered‐silicate nanocomposites

The biodegradability of poly(butylene adipate‐co‐butylene terephthalate) (PBAT) and PBAT/starch composites with layered silicates prepared by melt intercalation was evaluated with aerobic biodegradability tests in soil and in an aqueous medium containing activated sludge. Nonmodified montmorillonite (MMT) and octadecylamine‐modified montmorillonite (ODA‐M), known to give a microcomposite and an intercalated nanocomposite for PBAT, respectively, were used as layered silicates. After they were buried in the soil for 8 months, the PBAT/MMT microcomposite exhibited a higher weight loss than the control PBAT, whereas the PBAT/ODA‐M nanocomposite showed a lower weight loss instead. Also, the biodegradability test in the aqueous medium, by determining the biochemical oxygen demand, showed that the addition of MMT and/or starch to PBAT promoted biodegradation, whereas the addition of ODA‐M did not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

某化工厂树脂生产废水处理工艺的研究

树脂生产废水具有有机物浓度高,不易生物处理等特点,通过试验研究,先采用臭氧结合Fenton两级高级氧化对其预处理,降解有害和难降解物质,增加废水的可生化性,然后用混凝法进一步降低废水COD,最后增加废水在后续的A/O生化反应池中的停留时间,彻底降解污染物,使处理出水能够稳定达标。     

Reaction of Water–soluble Dyes with Ozone

Reaction of various kinds of water–soluble dyes with ozone was examined. It was found that the reaction of dyes with ozone improved their biodegradability, and the values of biochemical oxygen demand (BOD} and total organic carbon (TOC) of the ozonation products correlated with those of the theoretical TOC of the original dyes. In addition, the azo dyes had a tendency to be easily decomposed with ozone, and the decomposition of dyes was markedly accelerated when ozonation was accompanied by ultra–violet irradiation.     

A~2/O生化处理工艺对污水的处理

某奶牛养殖场因生产工艺改变,导致过量COD排入废水收集系统,使污水处理站不能正常运转。为达到GB 18918—2002《城镇污水处理厂污染物排放标准》一级A要求,需对现有污水处理系统进行改扩建,以满足现有水量和水质处理要求。该奶牛养殖场污水CODCr浓度高,可生化性强,应用EGSB反应器,采用典型A2/O生化处理工艺,辅以臭氧深度氧化处理,可以实现排放水达到《城镇污水处理厂污染物排放标准》一级A标准。奶牛养殖场周边无农田灌溉条件,必须将养殖废水深度处理后达标排放。应用本工艺,不仅实现排放水达标,而且为企业争取了更宽松的发展环境,极大地促进了企业的发展。     

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.     

O3/H2O2高级氧化法预处理酒精废水的实验研究

实验探讨了O3/H2O2高级氧化法预处理某制药酒精废水过程中H2O2投加量、pH值、反应时间、臭氧发生器氧气流量等因素对CODCr去除率的影响。实验得出的最佳反应条件是：H2O2投加量98 mmol/L,pH值11,氧气流量60 L/h,反应时间90 min,在最佳条件下反应后废水CODCr去除率46.3%,TOC去除率50.5%,B/C从0.08提高到0.32,废水可生化性明显提高,能够满足后续生化处理的需要。     

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.