[Carbon Emission Characteristics and Influencing Factors of Typical Processes in Drinking Water Treatment Plant].

Based on the actual operating conditions and data monitoring, the carbon emission characteristics of typical processes of a drinking water treatment plant (DWTP) in Tianjin were studied. The total carbon emission intensity measured by CO2-eq was 0.254 kg·m-3, and the proportion of carbon emissions from electricity consumption and reagent consumption was 81.76% and 9.15%, respectively. The key carbon emission sectors of electricity consumption were the water supply pump house, ultrafiltration membrane process, and inlet pump house, which accounted for 50.99%-73.51%, 17.64%-20.70%, and 17.97%-22.40% of the total carbon emission from electricity consumption in the DWTP, respectively. The contribution of sodium hypochlorite to the carbon emission of reagent consumption was 89.12%-90.30%, followed by ferric chloride, PAC, and ammonium sulfate. In the traditional water purification process, the carbon emission intensity of the process unit was in the order of inlet pump house > rapid filter > sedimentation tank. The order in the ultrafiltration membrane advanced treatment process was inlet pump house > ultrafiltration membrane > mechanical coagulation > clarification tank. The carbon emission intensity of the rapid filter process and the ultrafiltration membrane process were 0.070 9 kg·m-3 and 0.109 0 kg·m-3, respectively. The ultrafiltration membrane process could save 23% of the reagent consumption, and its carbon emission of electricity consumption was twice that of the traditional treatment process. The analysis of factors affecting carbon emission in key sectors showed that the raw water quality parameters such as turbidity, pH, ammonia nitrogen, temperature, etc., were significantly correlated with the carbon emission intensity of sodium hypochlorite. There was a significant linear regression relationship between ex-factory water pressure, daily water supply, and carbon emission intensity of the water supply pump house. The control measures of water quality and water pressure can effectively reduce the carbon emissions of the DWTP.

Pilot scale evaluation on ferric floc sludge concentration with pelleting flocculation blanket process.

Pelleting flocculation blanket (PFB) process has been successfully applied to high turbidity suspensions for high efficient solid/liquid separation. In this paper, by using the PFB process, a dynamic experimental study was carried out on concentrating ferric flocs sludge with a scale of 1.3-5.4 m(3)/h. The pilot experiment aimed to optimize the conditioning system and determine the operational parameters. Under the raw sludge concentrations of 103-1,154 mg/L, the system could achieve ideal conditioning effect with polyacrylamide (PAM) dosages of 0.3-2.7 mg/L, agitation speed of 10 rpm, and water up-flow rates of 18-48 m/h. Under the experimental conditions, the increase of polymer dosage would improve effluent turbidity and pellets settling behaviour, the moderate up-flow rate had no marked effect on treatment results, while too large surface loading could worsen effluent turbidity. The experimental results also revealed that there existed an approximately linear relationship between the raw sludge concentration and optimum PAM dosage, that is, the optimum dosage of PAM increased synchronously as the raw sludge concentration increased. While the relationship between the raw sludge concentration and maximum up-flow rate reflected another linear dependence, namely, the maximum up-flow rate would decreased linearly as the raw sludge concentration increased.

[Removing efficiency study on Cyclops cooperating with water treatment process by alternative oxidants].

The synergic removal effect on Cyclops was studied with 4 kinds of dosages of pre-oxidants such as chloramines, chlorine, O3 and potassium permanganate composite followed by different sets of clarification treatment process pilot systems. The removal mechanisms of Cyclops in different treatment units were analyzed. The experiments results show that the inactivation rate of chlorine (25%) is the highest compared with the chloramines (21%), potassium permanganate composite (8%) and O3 (9%) in the pre-oxidation stage, while the removal rate is changed after the filtration and the sequence is chloramines (90%) > chlorine (88%) > O3 (83%) > potassium permanganate composite (80%). Only chloramines can remove Cyclops by 100% of removal rate with the treatment process with the conventional active carbon unit. The 100% of removal effect doesn't depend on the highest inactivation rate,but the reasonable cooperation between the pre-oxidation and the clarification treatment process. The size of Cyclops and its life activity are the important influencing factors. The individual removal rate of filtration unit is the highest with no lower than 50%. The removal effect of air-flotation unit is influenced by the size of Cyclops and its life activity.

[Influence of catalytic ozonation process on suppressing bromate formation potential in drinking water treatment].

An investigation is given to the bromate formation of catalytic ozonation in treating drinking water. It is shown that the c x t value of ozone depletion stage plays a more important role in BrO3(-) formation. Catalyst addition not only reduces the residual ozone content by 60.0% - 77.4% but also extends the ozone ID stage time from 4.3 min to 6.8 min, which makes the ozone c x t value shorter. A full-scale study indicates a very effective strength and performance of catalytic ozonation in controlling BrO3(-) formation and it is able to suppress BrO3(-) formation potential by 51.7% on average.

Disinfection by-products and their precursors in a water treatment plant in North China: Seasonal changes and fraction analysis.

A one-year-long monitoring project was conducted to assay the concentrations of THMs, HAAs and their formation potential along the conventional process in a water treatment plant in North China. Subsequent investigations of organic matter fractionation and the contribution of the algae to the precursor were also conducted to trace the source of the DBPs. The results showed that the concentration of DBPs and their formation potential varied with the seasons. The highest concentrations of THMs and the highest HAAs formation potential, each almost 500 microg/L, were detected in autumn and the lowest were in spring, no more than 100 microg/L. Both organic matter and algae were found to be important DBP precursors. The hydrophobic acid fraction in dissolved organic matter has the highest formation potential for both THM and HAA. Algae contribute about 20% to 50% of the total formation potential during an algal bloom. The efficiency of each unit process for DBPs and precursors was also assayed. Unfortunately, the conventional drinking water treatment process is limited in its efficiency for precursor removal. The pre-chlorination and filtration process had a negative effect on DBP or precursor removal.

[Determining factors on the steady operation of immersed membrane process].

Target at the steady operation state, a pilot-scale test on the treatment of Luanhe source water was carried out using the process of coagulation-immersed membrane. The effect of membrane flux and water making period and raw water quality was systematically studied by means of trans-membrane pressure (TMP). The results show that the coagulation-immersed membrane process can control membrane fouling better and keep a steady operation state when membrane flux is 53.3 L/(m2 x h) and water producing period is 30 min. Water temperature change is one of the important factors, and the TMP of each filtration period can increase 76% from high temperature to low temperature raw water. Enhanced flux maintenance (EFM) integrated with chemical clean is a good control measure of membrane fouling.

Simultaneous control of microorganisms and disinfection by-products by sequential chlorination.

OBJECTIVE: To introduce a new sequential chlorination disinfection process in which short-term free chlorine and chloramine are sequentially added. METHODS: Pilot tests of this sequential chlorination were carried out in a drinking water plant. RESULTS: The sequential chlorination disinfection process had the same or better efficiency on microbe (including virus) inactivation compared with the free chlorine disinfection process. There seemed to be some synergetic disinfection effect between free chlorine and monochloramine because they attacked different targets. The sequential chlorination disinfection process resulted in 35.7%-77.0% TTHM formation and 36.6%-54.8% THAA5 formation less than the free chlorination process. The poorer the water quality was, the more advantage the sequential chlorination disinfection had over the free chlorination. CONCLUSION: This process takes advantages of free chlorine's quick inactivation of microorganisms and chloramine's low disinfection by-product (DBP) yield and long-term residual effect, allowing simultaneous control of microbes and DBPs in an effective and economic way.

[Optimal process combination for control of disinfection by-products and precursors during high algae laden period].

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.

[Influence of water source switching on water quality in drinking water distribution system].

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.

[Analysis of the characteristics of corrosion scale in drinking water distribution systems].

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.

[Plant scale test of a new efficient poly-aluminum chloride].

To meet the requirement of improved water quality, the economic water treatment process could be achieved by systematic coagulant selection and optimization of coagulation process. The experimental results show that the new coagulant developed has significantly improved the water quality, with marked modification of the particle size distribution feature after sediment and improved filtration efficiency. The organic removal ability, as shown by low TOC and UV254 in the finished water, is also significantly improved and also verified by using resin absorption characterization method. The TTHMFP for the source water is 20.98 microg/L and 11.01 microg/L for the traditional process. By using the new coagulant the TTHMFP is further decreased to 6.40 microg/L. With application of the new coagulant, the treatment costs are significantly decreased with further improved and simplified treatment process.

[Analysis of influence factors and control methods on iron release phenomenon in drinking water distribution system].

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.

[Simultaneous control of microorganism, disinfection by-products and bio-stability by sequential chlorination disinfection].

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.

[Study on influence between activated carbon property and immobilized biological activated carbon purification effect].

By means of immobilizing five kinds of activated carbon, we studied the influence between the chief activated carbon property items and immobilized bioactivated carbon (IBAC) purification effect with the correlation analysis. The result shows that the activated carbon property items which the correlation coefficient is up 0.7 include molasses, abrasion number, hardness, tannin, uniform coefficient, mean particle diameter and effective particle diameter; the activated carbon property items which the correlation coefficient is up 0.5 include pH, iodine, butane and tetrachloride. In succession, the partial correlation analysis shows that activated carbon property items mostly influencing on IBAC purification effect include molasses, hardness, abrasion number, uniform coefficient, mean particle diameter and effective particle diameter. The causation of these property items bringing influence on IBAC purification is that the activated carbon holes distribution (representative activated carbon property item is molasses) provides inhabitable location and adjust food for the dominance bacteria; the mechanical resist-crash property of activated carbon (representative activated carbon property items: abrasion number and hardness) have influence on the stability of biofilm; and the particle diameter size and distribution of activated carbon (representative activated carbon property items: uniform coefficient, mean particle diameter and effective particle diameter) can directly affect the force of water in IBAC filter bed, which brings influence on the dominance bacteria immobilizing on activated carbon.

[Comparative study on the organic matter removal in polluted raw water by different techniques at integrated pilot plant].

The traditional technique, preozonation technique, granular activated carbon adsorption technique and ozone-biological activated carbon technique were compared on its removal efficiency of organic matter and the THMs formation potential (THMFP) as well. It was found that, as compared with the former two techniques, the last two were more effective in organic matter removal, and the efficiency reached 75% - 90%, while the former only at 50% - 60%. The waterworks that adopted the Grade II source raw water were suggested to use the conventional techniques and seasonal preozonation techniques, while the others were suggested to alternatively select GAC or BAC technique to meet the request of new water quality criterion.

Iron stability in drinking water distribution systems in a city of China.

A field study on the estimation and analysis of iron stability in drinking water distribution system was carried out in a city of China. The stability of iron ion was estimated by pC-pH figure. It was found that iron ion was unstable, with a high Fe(OH)3 precipitation tendency and obvious increase in turbidity. The outer layer of the corrosion scale was compact, while the inner core was porous. The main composition of the scale was iron, and the possible compound constitutes of the outer scale were a-FeOOH, gamma-FeOOH, alpha-Fe2O3, gamma-Fe2O3, FeCl3, while the inner were Fe3O4, FeCl2, FeCO3. According to the characteristics of the corrosion scale, it was thought that the main reason for iron instability was iron release from corrosion scale. Many factors such as pipe materials, dissolved oxygen and chlorine residual affect iron release. Generally, higher iron release occurred with lower dissolved oxygen or chlorine residual concentration, while lower iron release occurred with higher dissolved oxygen or chlorine residual concentration. The reason was considered that the passivated out layer of scale of ferric oxide was broken down by reductive reaction in a condition of low oxidants concentration, which would result more rapid corrosion of the pipe and red water phenomenon.

[Optimal process combination for control of disinfection by-products and precursors].

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.

[Improvement of concentration method for detecting genotoxic activities of drinking water using umuC-test].

umuC-test is an effective method to determine the genotoxic activity. In this study, the highest genotoxic activity was found exactly at 37 degrees C by modifying original condition of umuC test. Effects of concentration methods on the genotoxic activity was studied, and it was found that the HLB solid phase extraction is most effective to extract the genotoxic chemicals from a drinking water when using acetone as eluant. The fate of genotoxic activity in drinking water treatment process was also studied, and chlorination promoted the induction of genotoxic activity.

[Controlling of biological stability in drinking water by purification processes].

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.