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Modified jar tests were performed in order to compare performances of coagulants treating, by direct filtration, raw water having a low turbidity and dissolved organic carbon. The object of this direct filtration is to produce water with a turbidity equal to or less than 0.10 NTU. The tests comprise a coagulation step with a laboratory flocculator, followed by a filtration step on a granular medium. Two poly aluminium silicate sulphates (PASS 100 and PASS 55), poly aluminium chloride (PACl), aluminium sulphate (alum), Ferriclear (prehydrolized ferric sulphate) and ferric chloride were studied. It was observed that all these coagulants are capable of lowering the turbidity of filtered water to 0.10 NTU or even less. Among the aluminium-based coagulants, PACl seems to be the most effective; while for iron-based coagulants, ferric chloride performs best. Although the doses are higher, alum offers a commercial advantage over the other aluminium-based coagulants because it costs less. When the turbidity object...

It was observed that biodegradable dissolved organic carbon (BDOC), measured by a fixed biomass method, in samples recarbonated with sodium bicarbonate, were always lower than those obtained in similar non recarbonated samples. Biomass used for all measurement was developed and sustained with non-recarbonated water (base water). The increase of alkalinity, pH and sodium concentration resulting from recarbonation seems to affect BDOC values. Results have shown little variation of BDOC (0.1 to 0.2 mg l−1 C) when the sodium concentration is raised from 3 mg l−1 (base water; alkalinity = 25 mg l−1 as CaCO3) to 40 mg l−1 (recarbonated water; alkalinity = 100 mg l−1 as CaCO3). However, when sodium concentration was increased to 109 mg l−1 (recarbonated water; alkalinity = 250 mg l−1 as CaCO3) important underestimation of BDOC (0.4 mg l−1 C to 0.6 mg l−1 C) occurred. In order to obtain better results, it was decided to adapt the biomass to the physico-chemical characteristics of each water for 45 days, 80 days a...

Bioreactors performing at a stable temperature of 20°C were used to achieve a rapid determination of the amount of biodegradable dissolved organic carbon (BDOC) present in ozonated water. Two feed modes, continuous feed and batch feed, were compared and evaluated. Bioreactors fed from holding tanks filled weekly with water passed through 1 and 75 µm filters were found to perform better in the short term (7 months after start-up) than those fed continuously with water filtered on 75 µm, in terms of the reduction in the amount of DOC between the intake and outflow points of the bioreactors, or BDOC (biodegradable dissolved organic carbon). It is believed that the difference in performance of batch-fed and continuously-fed bioreactors can be attributed to the more rapid bacterial colonization of batch-fed bioreactors. Moreover, it was observed that biological growth in the prefilter had an important role in the overall removal of BDOC through the continuously-fed bioreactor system.

This study was undertaken to evaluate the newly developed biofilm reactor for the measurement of biodegradable dissolved organic carbon (BDOC) in drinking water. This method enables rapid BDOC determination which would be ideally suited for the dynamic measurement of treatment plant BDOC variations in cases where reactor performance is stable with changing water quality. The biofilm reactors were found to best operate at constant temperature (19–23 °C). BDOC performance was found to be unhindered in low substrate, oligotrophic waters. BDOC values obtained using a suspended-inoculum BDOC measurement technique correlated positively with biofilm reactor BDOC values, although significant scatter was observed.

A major strategy to reduce or prevent the formation of undesirable by‐products is to reduce chlorine demand before the application of chlorine. The major objective of this study was to evaluate the performance of different water treatment processes at full scale, specifically the combination of ozonation and biological activated carbon (BAG) filtration, for the removal of chlorine demand over a range of natural organic matrix and water temperature (l°‐23 °C). Both long term and short term chlorine demand were measured using a 2:1/C12:TOC ratio and pH 7,0 phosphate buffer at 20 °C in darkness. Results show that chlorine demand increases over a period of 200 hours and that long term chlorine demand can be modeled using a second order relation. Chlorine demand can be reduced by 55% for short term (4h) and by 61% long term (168h) by coagulation, floculation and sedimentation. The net effect of ozonation is variable depending on the prevalent oxidation conditions and on the organic matrix. In warm tem...