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In recent years, chlorine-resistant bacteria were detected in drinking water distribution systems which threatened the drinking water safety. Our group detected one strain named Mycobacteria mucogenicum from the drinking water distribution system of a city in south China. This paper studied chlorine resistance and mechanism of Mycobacteria mucogenicum. Inactivation experiments of one strain Mycobacteria mucogenicum were conducted with free chlorine, monochloramind and chlorine dioxide. The CT values of 99.9% inactivation by free chlorine, monochloramine and chlorine dioxide were detected as (76.25 +/- 47.55)mg.min.L-1, (1396 +/-382)mg.min.L-1, (13.5 +/- 4.9) mg.min L-1. Using transmission electronmicroscopy (TEM) observed the inactivation process of Mycobacteria mucogenicum. The bacteria surface hydrophobic of Mycobacteria mucogenicum was 37.2%. Mycobacteria mucogenicum has a higher hydrophobicity than other bacteria which prevented the diffusion of chlorine into cells. Mycobacteria mucogenicum is more resistant to chorine than other bacteria.

Inactivation experiments of seven strains of chlorine-resistant bacteria, isolated from a drinking water distribution system, were conducted with four kinds of disinfectants. All the bacteria showed high resistance to chlorine, especially for Mycobacterium mucogenicum. The CT value of 99.9% inactivation for M. mucogenicum, Sphingomonas sanguinis and Methylobacterium were 120 mg x (L x min)(-1), 7 mg x (L x min)(-1) and 4 mg x (L x min)(-1), respectively. The results of inactivation experiments showed that chlorine dioxide and potassium monopersulfate could inactive 5 lg of M. mucogenicum within 30 min, which showed significantly higher efficiency than free chlorine and monochloramine. Free chlorine was less effective because the disinfectant decayed very quickly. Chloramination needed higher concentration to meet the disinfection requirements. The verified dosage of disinfectants, which could effectively inactivate 99.9% of the highly chlorine-resistant M. mucogenicum within 1 h, were 3.0 mg/L monochloramine, 1.0 mg/L chlorine dioxide (as Cl2), and 1.0 mg/L potassium monopersulfate (as Cl2). It was suggested that the water treatment plants increase the concentration of monochloramine or apply chlorine dioxide intermittently to control the disinfectant-resistant bacteria.

Red water phenomenon occurred in some communities of a city in China after water source switch in recent days. The origin of this red water problem and mechanism of iron release were investigated in the study. Water quality of local and new water sources was tested and tap water quality in suffered area had been monitored for 3 months since red water occurred. Interior corrosion scales on the pipe which was obtained from the suffered area were analyzed by XRD, SEM, and EDS. Corrosion rates of cast iron under the conditions of two source water were obtained by Annular Reactor. The influence of different source water on iron release was studied by pipe section reactor to simulate the distribution systems. The results indicated that large increase of sulfate concentration by water source shift was regarded as the cause of red water problem. The Larson ratio increased from about 0.4 to 1.7-1.9 and the red water problem happened in the taps of some urban communities just several days after the new water source was applied. The mechanism of iron release was concluded that the stable shell of scales in the pipes had been corrupted by this kind of high-sulfate-concentration source water and it was hard to recover soon spontaneously. The effect of sulfate on iron release of the old cast iron was more significant than its effect on enhancing iron corrosion. The rate of iron release increased with increasing Larson ratio, and the correlation of them was nonlinear on the old cast-iron. The problem remained quite a long time even if the water source re-shifted into the blended one with only small ratio of the new source and the Larson ratio reduced to about 0.6.

This study investigated the growth characteristics of iron bacteria on cast iron and relationship between suspended and attached iron bacteria. The steady-state growth of iron bacteria would need 12 d and iron bacteria level in effluents increased 1 lg. Hydraulics influence on iron bacteria level and detachment rate of steady-state attached iron bacteria was not significant. But it could affect the time of attached iron bacteria on cast-iron coupons reaching to steady state. When the chlorine residual was 0.3 mg/L, the iron bacteria growth could be controlled effectively and suspended and attached iron bacteria levels both decreased 1 lg. When the chlorine residual was more than 1.0 mg/L, it could not inactivate the iron bacteria of internal corrosion scale yet. There was little effect on inhibiting the iron bacteria growth that the chlorine residual was 0.05 mg/L in drinking water quality standard of China. The iron bacteria on coupons reached to steady state without disinfectant and then increased the chlorine residual to 1.25 mg/L, the attached iron bacteria level could decrease 2 lg to 3 lg. Under steady-state, the suspended iron bacteria levels were linearly dependent on the attached iron bacteria. The control of iron bacteria in drinking water distribution systems was advanced: maintaining the chlorine residual (0.3 mg/L), flushing the pipeline with high dosage disinfectant, adopting corrosion-resistant pipe materials and renovating the old pipe loop.

Halogen disinfection by-products of four chlorined disinfection processes with long contact time in distribution system was compared in the work. These four disinfection processes are free chlorine, monochloramines, free chlorine disinfection in clearwelles while chloramines in distribution system, sequential chlorination disinfection with short-term free chlorine plus chloramines. According to the research, free chlorine generates most trihalomethanes (THMs) and haloacetic acids (HAAs) both in clearwells and distribution system, while monochloramines barely yield halogen DBPs. Free chlorine disinfection in clearwelles while chloramines in distribution system could reduce 9.6% of THMs and 42% of HAAs in 24 h contact time of distribution system compared with free chlorine. But free chlorine has contacted with water for 2 h in this process, halogen DBPs have been yielded substantially. Process of sequential chlorination disinfection could control DBPs more effectively due to keeping a short contact time of free chlorine and water. 48% of THMs and 72% of HAAs are reduced in 24h compared with free chlorine. In conclusion, sequential chlorination disinfection is a more effective disinfection process for controlling DBPs and water safety.

Tastes and odors problems (TOs) in China and studies on TOs are reviewed, especially on aspects of the present situation in China, sources of TOs in water, TOs qualitativequantitative technology, odorant composing characters, removal technologies and processes on typical odorant in drinking water. This review aims to elucidate that besides microbial metabolism product such as geosmin and 2-MIB, organic anaerobic decomposition product such as thiol-thioether were also main odorant in drinking water of China. Thiol-thioether odorant which was found in drinking water of Dongguan in 2006 for the first time, was proved to be the main odorant in Taihu Lake drinking water risk in 2007 as well. Geosmin and 2-MIB were more easily removed by adsorption than oxidation, but thiol-thioether was easily removed by oxidation not by adsorption. In order to cope with TOs in different water source, different season and different odorant,studies on odorant composing character, removal technology, mechanism and process of typical odorant should be carried out as soon as possible in China.

Two-points-short-term free chlorine plus chloramines disinfection process was used in conventional treatments of water supply. The process is adding chlorine at the start of filtration and clear well respectively, and then after a few minutes chlorine disinfection in clear well adding ammonia to change the chlorine to chloramines. The point of chlorine dosing move up to the filtration process can decrease disinfection by-product yield and control bio-film growth in filtration process. Compared with adding equal quantity chlorine once, this process reduced 51.6% of THMs and 46.7% of HAAs. HPC result also showed advantage in microorganism controlling.

To eliminate the odor in drinking water of one City in China, a study was performed on the typical odorant removal technology and removal processes. Its results showed that as typical odorants, ethanethiol was effectively removed by oxidation and geosmin and 2-MIB were removed by both oxidation and adsorption, but geosmin and 2-MIB's adsorption effect was better than oxidation. When thiol and thioether in raw water was less than 20 microg/L, furthermore, there was not any other odorant, potassium permanganate oxidation should be equipped with enhanced coagulations. When geosmin and 2-MIB in raw was less than 30 ng/L, activated carbon adsorption should be equipped with enhanced coagulations. When thiol and thioether in raw water was more than 20 microg/L, or geosmin and 2-MIB was more than 30 ng/L, ozone-activated carbon process should be added after the conventional water treatment process. When thiol and thioether in raw water was more than 150 microg/L, or geosmin and 2-MIB was more than 100 ng/L, preoxidation or adsorption of powder activated carbon at intake should be combined with ozone-activated carbon according to the odorant composing.

The non-nitrification pathway for NH4+ -N removal in pilot-scale drinking water biological treatment processes and its possible mechanism were investigated through calculating N and DO stoichiometric balance. With more than 2 mg/L NH4+ -N in the influent, for the fluidized bed bioreactor (FBBR), the total of NH4+ -N, NO2(-) -N, NO3(-) -N in the influent was 0.91 mg/L higher than that in the effluent, and for the biofilter, its DO consumption was 2.90 mg/L less than the stoichiometric amount. The results suggested that nitrogen loss occurred in both reactors and a part of NH4+ -N was removed through non-nitrification pathway. Because the utilization of phosphorus and organic matters was independent of nitrogen loss, the assimilation and denitrification could be excluded from the possible mechanisms. Because the very low C/N in the influent and the accumulation of NO2(-) -N in the reactors were similar with the wastewater biological processes, the "autotrophic removal of nitrogen" was regarded as the most probable non-nitrification pathway. In this mechanism, the couple of short-cut nitrification and ANAMMOX (or OLAND) leading to the transformation of NH4+ -N and NO2(-) -N into gaseous N2 was responsible for the nitrogen loss in drinking water biological processes.

Reaction kinetics of ethanethiol oxidation with potassium permanganate in water was studied, and the effect of ethanethiol oxidation in raw water under coagulation condition has been investigated. The results showed that the oxidation reaction of ethanethiol by potassium permanganate was very efficient, the removing effect could be more than 90%. The rate of ethanethiol decomposition by potassium permanganate in aqueous solution followed second-order kinetics. When potassium permanganate was excessive, pseudo-first-order rate and concentration of potassium permanganate followed the equation: k' = 0.025 [KMnO4] - 0.008. And then, the second-order reaction rate constant was k = 0.025 L/(min x mg). The removal of ethanethiol in raw water by potassium permanganate under coagulation condition was poorer than in pure water condition, So predicted concentration of potassium permanganate was lower than real concentration.

Traditional pre-chlorination process would lead to high yield of DBPs during high algae laden period. It had been compared that the efficiency of control disinfection by-products and their precursors by two classes and total 7 kinds of process combination. Algae were proven to be important DBP precursor and it contributed about 20% of HAA and THM precursor. Air floatation was key process to remove algae and it could also reduce the precursor concentration in some degree. Ozone or potassium permanganate also had good efficiency on algae removal, and precursor as well. The best process combination for DBPs and their precursor removal is pre-oxidation of ozone or potassium permanganate plus conventional process plus ozone-BAC process. Sequential chlorination can reduce 42.0%-45.9% HAA yield and 22.5%-71.4% THM yield of free chlorination.

Batch-scale experiments were done to quantitatively study the effect of inorganic chemical parameters on iron release in drinking water distribution systems. The parameters include acid-base condition, oxidation-reduction condition, and neutral ion condition. It was found that the iron release rate decreased with pH, alkalinity, the concentration of dissolved oxygen increasing, and the iron release rate increased with the concentration of chloride increasing. The theoretical critical formula of iron release rate was elucidated. According to the formula, the necessary condition for controlling iron release is that pH is above 7.6, the concentration of alkalinity and dissolved oxygen is more than 150 mg/L and 2 mg/L, and the concentration of chloride is less than 150 mg/L of distributed water.

This study investigates the regularity of the change on the physical and chemical water qualities in the distribution system during the process of water source switching in A city. Due to the water source switching, the water quality is chemical-astable. Because of the differences between the two water sources, pH reduced from 7.54 to 7.18, alkalinity reduced from 188 mg x L(-1) to 117 mg x L(-1), chloride (Cl(-)) reduced from 310 mg x L(-1) to 132 mg x L(-1), conductance reduced from 0.176 S x m(-1) to 0.087 S x m(-1) and the ions of calcium and magnesium reduced to 15 mg x L(-1) and 11 mg x L(-1) respectively. Residual chlorine changed while the increase of the chlorine demand and the water quantity decreasing at night, and the changes of pH, alkalinity and residual chlorine brought the iron increased to 0.4 mg x L(-1) at the tiptop, which was over the standard. The influence of the change of the water parameters on the water chemical-stability in the drinking water distribution system is analyzed, and the controlling countermeasure is advanced: increasing pH, using phosphate and enhancing the quality of the water in distribution system especially the residual chlorine.

The determination measure for distribution of NOM removal by two mechanisms in BAC was established. In this method, the change in DOC and BDOC of inflow and effluent was used to evaluate the distribution and to determinate the effect of the different ozone doses on the adsorption and biodegradation in BAC. The ozonation increased the concentration of BDOC in 0.12 - 0.54 mg/L with ozone dose of 2 - 8 mg/L and BAC filtration decreased concentration of BDOC to 0.23 - 0.31 mg/L. Moreover the biodegradation distribution to remove the organic pollutants increased from 46% to 89% with ozone dose of 2 - 8 mg/L.

Some organic matter that have aromatic structure similar as humic acid are selected to conduct chlorination test, determined the formation of HAAs and THMs of tested matters, researched the relationship of the chemical structure of DBPFP with DBPs formation characteristics. The results indicated that: (1) The sequence of HAAs formation activity is p-Hydroxybenzoic acidp-Aminoacetophenoneo-Benzenediolm-Benzenediol; and THMs' s is m-Benzenediolp-Aminoacetophenone2-Hydroxy-p-aminoacetophenonep-Hydroxybenzoic acid. (2) The sequence of earlier chlorination reaction rate of HAAs is m-Benzenediolp-Aminoacetophenonep-Hydroxybenzoic acido-Benzenediol; and THMs' s is p-Hydroxybenzoic acid2-Hydroxy-p-aminoacetophenonem-Benzenediolp-Aminoacetophenone. (3) The substances that having the substituent group structure of para and ortho position are mostly format HAAs, and one's of having meta position are mostly format THMs. (4) On the benzene ring, hydroxyl group has the highest activity of forming DBPs, and the second is ketone group; amino-group is play a part of auxiliary forming para, ortho or meta position structure mainly; aldehyde and carboxyl group are inert function group; the function of methyl group is remain to be determined.

Scanning electron microscopy, X-ray fluorescence spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy were used to analyze the microstructure, chemical composition, crystalline structure and compound constitute of the corrosion scale from cast iron pipe and galvanized steel pipe in drinking water distribution systems. The outer of the corrosion scale was compact, while the inner was porous. Iron was the primary chemical element of the corrosion scale, and the composition of the scale was iron compounds. The outer scale were ferric compounds such as alpha-FeOOH, gamma-FeOOH, alpha-Fe2O3, gamma-Fe2O3, FeCl3, while the inner were ferrous compounds such as Fe3O4, FeCl2, FeCO3. The characteristics of the corrosion scale was lying on hydraulic conditions and water quality in distribution systems, and the characteristics of iron pipe materials.

The ozonation can increase biodegradability of water and the biofilter after ozonation can increase biostability of water. The result shows that with different doses of ozone between 2 and 8 mg/L, ozonation can increase AOC-P17, AOC-NOX and BDOC by 20.9%-85.5%, 42.1%-158.2% and 21.4%-84.4%, respectively. The optimum ozone dose for maximum AOC and BDOC formation is 3 mg/L. In the test, the AOC of effluent from BAC is lower than 50 microg/L (acetate-C). The AOC concentration is between 35.9 and 46.6 microg/L (acetate-C), and the effluent belongs to biostability.

Variation rule of iron in drinking water distribution systems was studied, and it was found that the iron released from the scale to the bulk water was the primary reason for iron overstep. The main chemical composition of the scale in cast iron pipe and galvanized steel pipe was iron in a northern city in China. In the drinking water distribution systems, when the value of dissolved oxygen or chlorine residual was low, the iron release phenomenon was severe. The reason for that was the passivation layer of the corrosion scale was destroyed in reductive condition and the result was a great amount of iron in ferrous form was released. According to the research results, the control methods for iron release and 'red water' phenomenon were indicated.

A high ammonia micropolluted source water advanced treatment for ammonia removal by biological activated carbon filter was tested. The removal rate of ammonia was high than 95% when influent concentration was under 1.0 mg/L. The removal rate decreased with the influent concentration increased when the ammonia concentration was in range of 1.5 - 4.9 mg/L and the influent DO was under 10 mg/L, and the minimum removal rate was about 30%. The key factor of restrict nitrification in BACF was the influent DO. When the influent ammonia concentration was high, the DO in water was depleted quickly by nitrify and hetetrophic bacteria in 0.4 m deep of filter and the filter layer was divided to aerobic zone and anoxic zone. The denitrification was occurred in the anoxic zone, and because of very low concentration of electron donor led to accumulation of the denitrification intermediates such as NO2-. Aerobic bacteria was existed in the anoxic zone.

A new safe chlorination disinfection process, the sequential disinfection process with short-term free chlorine plus chloramines was investigated its efficiency on control of indices of microorganism, disinfection by-products and bio-stability. This disinfection process may take the advantage of free chlorine's quick inactivation of microorganism and chloramines' low DBP yield and long-term residual. Thus, both control of microorganisms and DBPs can be achieved effectively and economically. The pilot test results show that safe chlorination disinfection process has a little better efficiency on total bacteria count, HPC and total coliform count than free chlorination disinfection, which indicate that free chlorine and chloramines might have the synergetic disinfection effect for their different attacking targets. It also had the same inactivation efficiency on polio virus and coliphage f2 as free chlorination in 120 minutes contact time. Sequential chlorination disinfection process could reduce 35.8% - 77.0% yield of trihalomethane and 36.6% - 54.8% yield of haloacetic acids. The poorer quality the water had, the more advantage the safe-chlorination disinfection had than free chlorination disinfection one. Moreover, sequential chlorination had better efficiency on bio-stability control than free chlorination.

In a pilot scale system, the formation and removal of BDOC and AOC were compared in the pre-treatment unit, traditional treatment unit and advanced treatment unit. The experimental results indicate that the COD(Mn) removal in a traditional process plus active carbon filter system is 30% and in a traditional process plus ozone and active carbon filter system is more than 50%. The AOC contents in the effluent of a traditional process plus active carbon filter system is below 50 microg/L. The optimum process combination in the research is: traditional process plus ozonation plus biological active carbon.

The inactivation of Escherichia coli with free chlorine and monochloramine was studied using bench-scale experiments in 0.03 mol/L phosphate buffered saline with pH 7.0 and at 20 degrees C. Inactivation data were fitted to Chick's law, Chick-Watson, Hom, Rational, Hom-Power law, Selleck model. A three-parameter Rational model incorporating a first-order disappearance term for free chlorine residual was found to best describe the observed inactivation of E. coli, and for monochloramine the two-parameter Selleck model was the best fit model.

It is compared that the efficiency of control disinfection by-products and their precursors by sequential-chlorination disinfection and traditional free chlorination disinfection following different processes combination. Compared with traditional chlorination, sequeutial chlorination, i. e. short-term free chlorine plus chloramine disinfection can lower 35.8% - 77.0% of trihalomethane formation and 36.6% - 54.8% of haloacetic acids formation. Moreover, the poorer the influent quality is, the more advantages sequential chlorination disinfection have over free chlorination disinfection. The formation of trihalomethane and haloacetic acids by sequential chlorination following the simplest traditional process is even less than their formation by free chlorination following the most complex process, pre-ozonization plus traditional one and ozonization-active carbon process. The results show that ozonization-active carbon process and pre-ozonization have better efficiency on control of disinfection by-products and their precursors. We recommend that water plants apply the sequential chlorination disinfection and ozonization-active carbon process.

GAC-sand dual media deep bed dissolved air flotation/filtration (GSDDB-DAFF) is a new integrated process, its characteristics include: integration of dissolved air flotation and filtration, GAC-sand dual media deep bed filtration, integration of general treatment and advanced treatment. When algae-laden raw water was treated with the new process. The result showed that removal percentage of algae was 95.1%, outlet algae-count was 4.30 x 10(5) cell/L. Removal percentage of chlorophyll-a was 92.2%, outlet chlorophyll-a was 0.88 microg/L. Outlet turbidity was 0.18 NTU, removal percentage of UV254 was 54.3%, outlet UV254 was 0.016 cm(-1), Removal percentage of OC was 63.6%, outlet OC was 0.78 mg/L; outlet had no odor; removal percentage of color was 86.4%, outlet color was 3; outlet Al-residual was 0.011 mg/L which accorded with the quality standard of drinking water. Run time of filter was 36 h, UFRV (Unit Filter Run Volume) was 504 m3/m2.

Methods of the enumeration of total bacteria and Coliform in drinking water were researched in this paper. The differences between heterotrophic plate count and direct viable count method were compared. It is concluded that the total number of bacteria in R2A medium is one order of quantity higher than the traditional plate count agar, and the results of acridine orange direct counts (AODC) is the highest. Some different staining methods in direct viable count were also compared in this paper, such as nalidixic acid, CTC staining and BacLight staining. The proportion of the live bacteria to the dead is about 10%.