The drinking water treated by water treatment plant (WTP) usually has an excess of assimilable organic carbon (AOC) in distribution systems in south Taiwan. They will cause the growth of heterotrophic plate count (HPC) and deterioration of water quality in pipeline of distribution systems. Recently, part of traditional purification processes were changed into advanced processes in WTP. The past researches showed the combined advanced processes ultrafitration (UF) / reverse osmosis (RO) in south WTP in Taiwan has the removal problems of AOC in above UF / RO processes because the organic compounds in raw water caused a fouling layer which was formed on the membranes surface. These problems made the back-wash frequency increasing, short membrane life and raising cost. The study combines activated carbon and membrane bioreactor (MBR) to explore the removal efficiency of drinking water in laboratory. The system showed the removal efficiencies of dissolved organic carbon (DOC) and AOC were 57% and 36%, respectively in average. More, the system showed the removal efficiencies of DOC and AOC were 81% and 66%. The results of this research showed good removal efficiency was found in AOC and DOC. Good quality of biological stability, removal of organic compounds, low cost in building and maintaining were reached.

In the process of traditional water treatment, the humic acid and fulvic acid can be oxidized by chlorination; besides, it also produces small molecular organic compounds at the same time. Coagulation, flocculation, and sedimentation can reduce the concentration of the Assimilable Organic Carbon (AOC) significantly. An example of Ping-Ding water treatment plant was performed with sampling twelve times monthly from December 2008 to November 2009, the strong influence of chlorine, and coagulation, flocculation on the AOC can be observed. Comparing to the removal efficiency of water process in Ping-Ding water treatment plant, the AOC presented much stably in the distribution systems. We observed the data on the mean concentration of monthly sampling related to the operation unit in the water treatment plant. The Total Organic Carbon (TOC), and the Dissolved Organic Carbon (DOC) had the same trend with AOC in the water treatment process; it showed that TOC, and DOC had well relation to AOC in Ping-Ding water treatment plant. However, scrutinizing single monthly sampling, we found that the concentration of AOC did not fix out with the concentration of TOC and DOC at the same time. Therefore, results indicate that the AOC is mainly related to the smaller organic molecules of the TOC. In the series of sampling, we divided the influence of climate factor into the dry season and the pour season. The research discussed the five analysis items in the final results and discussion¡GTOC, DOC, UV254, UV254/DOC, and AOC. Basically, the concentration of the five analysis items on the pour season is higher than the dry season; it indicates that the raw water¡¦s concentration of organic carbon in Ping-Ding water treatment plant is higher during raining days. This can express the high concentration of the UV254, UV254/DOC, and AOC in water treatment plant in our work.

Taiwan Water Supply Cooperation (TWSC) has upgraded traditional purification processes into advanced treatment systems in south Taiwan for many years. The removal efficiency of assimilable organic carbon (AOC) by ultrafiltration (UF) with reverse osmosis (RO) systems was 47% was lower than that of 62% by ozone with biological activated carbon system (BAC). In this work, we investigate the removal of AOC and disinfection by products formation potential (DBPFP) of raw water took from a water treatment plant by using BAC and membrane treatment units. BAC system of granular activated carbon(GAC) and powder activated carbon (PAC) showed two kind carbons have certain efficiency for AOC removal. Results we found could reach above 50% (from 44.28¡Ó9.84£gg acetate-C/L reduce to 20.93¡Ó4.25£gg acetate-C/L for GAC and from 45.92¡Ó17.75£gg acetate-C/L reduce to 21.23¡Ó4.25£gg acetate-C/L for PAC), when hydraulic retention time (HRT) in BAC reactor was at 1 hour. When HRT raised to 6 hours the concentration of AOC in effluent of BAC systems were reduced under 15 £gg/L, and removal efficiency could reach above 70%. The suggested limit level of AOC is 50 £gg/L of drinking water. In removal of DBPFP, BAC of two carbons has showed certain efficiency on trihalomethanes formation potential (THMFP) and haloacetic acids formation potential (HAA5FP). The results were done in removal of THMFP (from 20.54¡Ó6.48£gg/L reduce to 14.21¡Ó4.47£gg/L for GAC and from 24.64¡Ó6.74£gg/L reduce to 14.75¡Ó4.04£gg/L for PAC) and HAA5FP (from 39.64¡Ó10.38£gg/L reduce to 17.35£gg/L for GAC and from 17.86¡Ó5.13£gg/L reduce to 11.76¡Ó3.76£gg/L for PAC) in BAC reactors. They were all lower than national standard of drinking water (THMs 80£gg/L, HAAs 60£gg/L). It is believed that two kind carbons in BAC system could all reduce effectively on AOC and DBPFP to obtain high quality of drinking water with biological stability at HRT of 6 hours.

According to the literature, the deterioration of water quality in pipeline networks of water distribution is not solely due to the deterioration of raw water quality outlet from water treatment plants, but primarily due to the multiplication of microorganisms in water distribution pipelines, a phenomenon known as after-growth or re-growth. Presently, the most effective method of a biological stability in treated water for controlling microbial re-growth is by limiting nutrients, including nitrogen, phosphorus, and organic carbon. The content of assimilable organic carbon (AOC) within organic carbon is considered to be the most main factor for controlling the growth of microorganisms in the water distribution systems. The objects of this work were to study the Cheng Ching Lake Water Treatment Plant (CCLWTP) in Kaohsiung and the Gong Yuan Water Treatment Plant (GYWTP) in Chiayi. Water samples were collected once a month from December 2008 to November 2009. The major difference between the study objects was that front one is an advanced water treatment plant, and the other a traditional one. In order to understand the difference in biological stability between these two water treatment plants, AOC meaurement was conducted. The goals of this study were: (1) to understand the water purification process of advanced and traditional water treatment plants, and to understand the concentration in AOC fluctuation in their water distribution networks; (2) to learn about differences in how the two water treatment plants remove AOC, and to know where is improvement ; (3) to use program analysis to produce a simple formula and AOC-related water quality parameters for the two water treatment plants, providing AOC control and management strategies in the future. The results concluded that the raw water of the two water treatment plants was primarily a hybrid of hydrophobic and hydrophilic molecules, and the highest values of AOC were found in winter. The CCLWTP had an overall removal rate of 54 %, and the GYWTP had an overall removal rate of 36 %. The CCLWTP conformed to the additions of an advanced water purification unit, but the water treatment process was relatively complex. Its AOC concentration varied considerably during the course of the water treatment process, while that of the GYWTP showed more stable measurements. The CCLWTP used coagulation precipitation, rapid filtration, and biological activated carbon filtration to effectively remove the AOC. The coagulation precipitation unit used by the GYWTP was most effective process in the removal of AOC and rapid filtering was less effective one. The treated water of CCLWTP maintained an AOC concentration under 51 £gg acetate-C/L in its water distribution network, while the treated water of GYWTP mostly kept a concentration of AOC lower than 71 £gg acetate-C/L. Although the CCLWTP water pipe network had lower AOC values, it demonstrated unstable changes in levels of AOC concentration. This shows that oxidation and disinfectants in the water treatment process cannot successfully oxidize all organic matter into AOC. In contrast, the GYWTP showed a more stable removal in AOC content. For the artificial neural network system simulation, the simulation values of CCLWTP water treatment process and water distribution network are correlated less closely with the measured actual value than those of the GYWTP do. This is found to be mostly due to the relatively large fluctuations in AOC in the CCLWTP. The AOC values in the CCLWTP water treatment process and water distribution network are highly correlated to TOC, TDS, and NH3-N. For the GYWTP, AOC values were mostly correlated to TOC, temperature, and NH3-N. Finally, the two common factors for water quality at both water plants were TOC and NH3-N, we recommend that these two items can be taken into consideration to control and manage AOC in water treatment.

Growth of bacteria in drinking water distribution and storage systems can lead to the deterioration of water quality, violation of water standards, and increased operating costs. Growth or Regrowth results from viable bacteria surviving the disinfection process and utilizing nutrient in the water and biofilm to sustain growth. Factors other than nutrients that influence regrowth include temperature, residence time in mains and storage units, and the efficacy of disinfection. Tests to determine the potential for bacterial regrowth focus on the concentration of nutrients. Not all organic compounds are equally susceptible to microbial decomposition; the fraction that provides energy and carbon for bacterial growth has been called labile dissolved organic carbon, biodegradable organic carbon (BDOC), or Assimilable Organic Carbon (AOC). Easily measured chemical surrogates for AOC are not available now. As alternative to chemical methods, bioassays have been proposed. Assimilable Organic Carbon (AOC) is that portion of the biodegradable organic carbon that can be converted to cell mass and expressed as a carbon concentration by means of a conversion factor. In this study, two organisms, namely Psuedomonas fluorescens strain P17 and Spirillum species NOX were selected for the AOC determination. The growth of the bacteria was determined by periodic colony counts with spread plate technique on LLA (Lab-Lemco nutrient agar) cultivation medium until the growth reached maximum (maximum colony count, Nmax). Results showed that AOC follows a trend based on the climatic and seasonal changes (local climate) with peaks in summer and low during winter season and vice versa in term of AOC removing capability. In addition to confirm AOC removal rate in biofiltration bed was evaluated with a test column containing the same filling materials, Granular Activated Carbon (GAC). Long term test showed that GAC would last for forty weeks without any special treatment. Other result showed that biofiltration bed has a better removal efficiency rate 72% (average based on four year), than the test column 49% since it experience frequent back-washing, thus maintaining a healthy removal rate. In the test column change in total organic carbon was quite abnormal. AOC yearly distribution was also studied and differentiated into four stages. AOC removal of each stage was 48%, 70%, 83% and 77%. Total organic carbon concentration was much higher in the effluent 384 than influent 334 £gg C/L; later methionine was found in water sample (effluent) which strongly suggests that the indigenous microbes had been reducing organic material such as cystein to methionine thus increasing the organic carbon content of the effluent. The microbial growths inside the GAC test column is entirely based on the long term feed of water at the treatment plant. Several other parameters such as Scanning Electron Microscope (SEM), Excitation Emissions Fluorescence Matrix (EEFM), Molecular Weight and Amino acids detection were selected and coupled with the AOC to shed light on the working mechanisms of both GAC as filtration material and characteristics of indigenous microbes towards the removal of organic contaminants and changes they can bring about to the quality of clear water.

To improve water quality of drinking water, the Taiwan Water Supply Corp (TWSC) upgraded three water treatment plants (WTP), changing traditional treatment processes into two advanced membrane processes and one advanced ozonation processes in recent years. Membrane water treatment units of the water treatment plant comprise ultrafiltration (UF) and reverse osmosis (RO). And the advanced ozonation water treatment units comprise pellet softening, post-ozonation and biological activated carbon (BAC) adsorption. This study investigated the formation of disinfection byproducts (DBPs), dissolved organic carbon (DOC) and assimilable organic carbon (AOC) at two advanced water treatment plants (ATP) in Kaohsiung City, Taiwan, by implementing a sampling program. The purposes of this study include¡G(1) The evaluation of treatment efficiency of advanced water treatment plants. (2) Application of powdered activated carbon and membrane bioreactor in removing organic compounds in drinking water. TCM was by far the predominant species in the finished water, the average concentration of DPBs in this study at both plants were 13.97¡Ó4.18£gg/L and 21.49¡Ó10.59£gg/L of THMs for plant A and plant B, respectively. However, levels for DPBs compound are low in both plants and lower than the current national drinking water quality standards 80 £gg / L. But for anther typical DPBs (HAAs compounds), the average concentrations were 17.67¡Ó14.50£gg/L and 33.03¡Ó16.24£gg/L of HAA5 for plant A and plant B, respectively. DCAA and TCAA were the two major species of HAAs found in the two water samples under study. The sums of the two species represented in finished water were about 67% and 83% of HAA5 in A and plant B, respectively. The results showed that HAA5 concentration of all samples could meet current USEPA standards for drinking water quality. Importantly, our work show the advanced treatment processes have good removal on DPBs of treated water. In organic compounds removal, there is high efficiency by using post-ozonation combined with BAC, but low efficiency for membrane process due to the inhibition of electrical charge happened on surface of membrane. This inhibition is caused probably by high hardness and high ion strength in water. We found by combining BAC with membrane filtration process will effectively remove the organic compounds and lower the concentration of AOC for passing the limit value suggested in related researches of the world.

Activated carbon (AC) systems and reverse osmosis (RO) systems are commonly used point-of-use (POU) water filtration systems as the last barrier to remove trace-level contaminants in tap water to protect human health. Limited studies have been done to evaluate trace-level manganese and uranium removal in tap water. Additionally, undesired microbial growth in POU systems may reduce treatment efficiencies of POU systems and limited studies have been done to evaluate microbial growth potential in POU systems. The overall research objective of this study was to systematically evaluate the removal of metals and assimilable organic carbon in POU systems. AC systems were operated to 200% of their designed treatment capacities and RO systems were operated for three weeks. The results indicated that AC systems were generally ineffective to remove metals in drinking water, while metals were effectively removed in RO systems. The results showed that calcium and magnesium were not effectively removed in AC systems with removal efficiencies of less than 1%. Various factions of iron were removed with its removal efficiencies in AC systems ranged between 61% and 84%. Copper was effectively removed in AC systems with removal efficiencies greater than 95%, which was possibly related to its low influent concentration in drinking water (<30 μg/L). Both manganese and uranium were ineffectively removed from AC systems. Different from AC systems, RO systems were consistently effective to remove all metals. Calcium, magnesium, iron, and copper were all removed with removal efficiencies greater than 98%, while removal efficiencies of manganese and uranium in RO systems were above 95%. Assimilable organic carbon was effectively removed from all AC and RO systems and high variability of AOC removal efficiencies were observed, which may be attributed to the heterogenicity of biofilm and microbial growth in POU systems. The new knowledge generated from this study can help improve our understanding of emerging contaminant removal in POU systems and develop better strategies for the design and operation of POU systems to remove emerging contaminants in drinking water and mitigate their health risks to humans.

No description available.

Assimilable organic carbon (AOC) is a suspected contributor to growth of microbes, including pathogens, in plumbing systems. Two phases of research were completed to improve knowledge of AOC and other forms of organic carbon in premise plumbing. In the first phase, the AOC Standard Method 9217B was compared to a new luminescence-based AOC in terms of time, cost, convenience, and sources of error. The luminescence method was generally more accurate, as it better captured the peak growth of the test organisms. It was also less expensive and less time-consuming. A few approaches to improving the accuracy of the method and detect possible errors were also presented. In the second phase of research, the possibility of AOC generation in premise plumbing was reviewed and then tested in experiments. It has been hypothesized that removal of AOC entering distribution systems might be a viable control strategy for opportunistic premise plumbing pathogens (OPPPs), but if AOC was generated in premise plumbing systems this approach would be undermined. Possible sources of AOC creation in premise plumbing, which is herein termed "distribution system derived biodegradable organic carbon (DSD-BDOC)," include: leaching of organic matter from cross linked polyethylene (PEX) pipes, autotrophic oxidation of H2 generated from metal corrosion (e.g. sacrificial magnesium anode rods and iron pipes), rendering of humic substances more biodegradable by sorption to oxides such as Fe(OH)3, and accumulation of AOC on filters and sediments. The potential for various plumbing and pipe materials to generate AOC was compared in controlled simulated water heater experiments. Under the worst-case condition, generation up to 645 µg C/L was observed. IT was not possible to directly confirm the biodegradability of the generated organic carbon, and there were generally no correlations between suspected generation of organic carbon and either heterotrophic plate counts (HPC) or of bacterial 16S rRNA genes. DSD-BDOC was also explored in a simulated distribution system with two disinfectant types (chlorine and chloramine) and three pipe materials (PVC, cement, and iron). TOC increased with water age, probably due to leaching of organics from PVC and possibly the aforementioned DSD-BDOC due to autotrophic reactions of nitrifiers and iron-related bacteria. As before, relationships between the higher levels of organic carbon and either HPC or 16S were not observed. / Master of Science

This thesis is focused on technological processes during drinking water treatment. The emphasis is put on monitoring indicators of organic substances present in water and indicators of the biological stability of treated water. The experimental part is focused on the comparison of separation efficiency of drinking water treatment technological processes by monitoring of chemical oxygen demand, absorbance measured at 254 nm, bioseston, culturable microorganisms and assimilable organic carbon.