Ozonation of Humic Substances: Effects on Molecular Weight Distributions of Organic Carbon and Trihalomethane Formation Potential

Four different sources of humic substances were studied to determine the effects of ozonation on molecular weight-distributions, based on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Solutions of two soil-derived fulvic acids and a one soil-derived humic acid, as well as dissolved organic matter (DOM) associated with a natural water source were studied. Both gel permeation chromatography (GPC) and ultrafiltration (UF) were employed to define apparent molecular weight (AMW). Applied ozone doses ranged from 2.0 to 2.5 mg O₃/mg DOC. Overall samples of untreated and ozonated waters, as well as individual molecular weight fractions, were characterized according to DOC, UV absorbance, and THMFP. Ozonation resulted in a significant disappearance of higher AMW material with a corresponding increase in lower AMW material. Although little overall reduction in DOC concentration was observed, significant overall reductions in UV absorbance and THMFP levels were observed.     

Flocculation Effects of Ozone

There are numerous reports on coagulation/flocculation effects of preozonation, which cannot be interpreted by one single mechanism. About 7 basic processes are presently discussed. This paper presents results from drinking and wastewater treatment, indicating that preozonation effects can be explained with algae flocculation, with the destabilization of particles, and with polymerization of the dissolved organics. In view of the complexity of the systems, it is anticipated that several processes can be responsible, leading to an optimum ozone dosage.     

气浮——纤维过滤法和微絮凝纤维过滤——膜滤法处理洗浴废水的研究

采用两套处理工艺对洗浴废水处理进行试验研究。流程一采用“气浮＋纤维过滤”，流程二采用“微絮凝纤维过滤＋膜滤”。试验表明，采用这两种工艺均能使出水达到国家生活杂用水水质标准，且具有占地面积小、操作简单、出水水质稳定等优点，是行之有效的处理方法，详细地介绍了这两套流程的试验情况。     

Water Quality Improvements with the Use of Ozone at the Los Angeles Water Treatment Plant

At 600 mgd (2,270 ML/day), the recently completed Los Angeles Aqueduct Filtration Plant (LAAFP) is one of the world's largest water' treatment facilities utilizing ozone for pretreatment. The treatment process features direct filtration at rates of up to 13.5 gpm/ft² (33 m/h). Under the optimized full-scale operation, preozonation has resulted in significantly reduced THM levels and very low effluent turbidity with low operating costs.     

Ammonia,Nitrite and Nitrate Nitrogen Removal from Polluted Source Water with Ozonation and BAC Processes

Studies on the removal of ammonia-, nitrite-, and nitrate nitrogen with ozonation (O₃), sand filtration (SF), biological activated carbon (BAC), SF-BAC, and/or O₃-BAC processes were carried out in two pilot plants and a full scale plant, respectively. The results showed that all of the tested processes exhibited certain nitrogen removal efficiencies, of which both the O₃-SF-BAC and O₃-BAC processes were most effective and efficient in removing ammonia nitrogen, with mean removal efficiencies of some 90 and 80 percent, respectively.

Ozonation was found able to oxidize some organic nitrogen into ammonia, and nitrite ion into nitrate ion. It was also found out, with interest, that the O₃-BAC process can carry the nitrification process to the end under sufficient DO content, as well as more hydrocarbon substrates through ozonation that are more easily assimilated by some strains of nitrobacter that can multiply heterotrophically in its carbon beds. In the BAC process, both the DO and easily assimilated substrate contents were too low in its carbon beds due to no ozonation to sustain nitrobacter growth; but the nitrite conversion bacteria, like nitrosornas, can survive under such conditions. As a result, nitrite or nitrate ion content increased multiply in the effluents from BAC or O₃-BAC processes over their influents. respectively.

The removal mechanisms of various processes for the three forms of nitrogen were studied and discussed, and the optimum design parameters were determined as well.     

Ozone Versus Ozone/Peroxide Induced Particle Destabilization And Aggregation: A Pilot Study

This research compares the role of ozone and the conjunctive use of ozone plus hydrogen peroxide in particle destabilization and particle aggregation, and improvement in filtered water quality. Particle destabilization was observed at all doses of ozone and ozone/peroxide studied, whereas aggregation was observed with ozone only at lower doses (> 2 mg/L) and in conjunction with ozone/peroxide (all doses studied). As compared to alum alone, the ozone-plus-alum and ozone/peroxide-plus-alum treatments provided improved flocculation and better filtered water quality. In addition, each of these preoxidations significantly reduced alum requirements. Overall, in terms of particle destabilization and aggregation; i.e., effectiveness as a coagulation aid, Ozone/peroxide performed better than ozone.