Microbially Available Phosphorus Research Articles

Evaluation of pre-treatment technologies for phosphorous removal from drinking water to mitigate membrane biofouling

Membranes are widely used for the treatment of various solutions. However, membrane fouling remains the limiting factor for their usage, setting biofouling as the most severe type of it. Therefore, the production of biologically stable water prior to membranes is important. Since lack of phosphorus may hinder the growth of microorganisms, the aim of this research is to evaluate the effect of microbially available phosphorus (MAP) removal via affordable water pre-treatment methods (adsorption, biofiltration, electrocoagulation) on bacterial growth. Four cylindrical reactors were installed at an artificially recharged groundwater station. Further temperature influence and carbon limitation were tested for biofiltration technology. The amount of MAP and total cell count was measured by flow cytometry. The results showed that at lower temperatures electrocoagulation performed the best, resulting in complete MAP removal (detection limit 6.27x10-3μg P l-1). Sorbent demonstrated MAP removal of 70-90%. Biomass did not have any noteworthy results at +8°C, however, at +19°C MAP removal of around 80% was achieved. Main conclusions obtained within this study are: (i) tested technologies effectively eliminate MAP levels; (ii) temperature has a significant effect on MAP removal in a bioreactor, (iii) multi-barrier approach might be necessary for better P limitation that might prolong operating time of a membrane.

APPROBATION OF MICROBIALLY AVAILABLE PHOSPHORUS (MAP) DETERMINATION METHOD BY FLOW CYTOMETRY

Phosphorus (P) is among the most important nutrients required for bacterial growth. It has a great influence on microbial activity even at very small concentrations. Existing chemical methods are not able to determine P at low enough concentrations and to quantify biologically available phosphorus fractions. Therefore, a method of microbially available phosphorus (MAP) determination is used to quantify the amount of P at concentrations below 20 µg/l. Additionally, this method determines the amount of P that can be directly used by microorganisms.
 Originally it was determined by inoculating sample by Pseudomonas fluorescens (now Ps. brenneri) P17 strain and spread-plated on R2A agar for enumeration. Further, a more rapid method was developed by replacing heterotrophic plate count (HPC) by flow cytometry (FCM).
 In this paper the use of FCM for MAP determination is validated and compared with HPC method. The results of calibration are presented. The original pure P17 strain was used as inoculum and standards with different PO4-P concentrations were inoculated at 30°C. The gained yield factor by FCM was 1.59x108. FCM results showed strong correlation (R2=0.99) with HPC results, as pure culture was used. Therefore, flow cytometry is a rapid alternative to heterotrophic plate count method for microbially available phosphorus determination.

An improved method for determining microbially available phosphorus in drinking water

Microbially available phosphorus (MAP) is the labile phosphorus that is readily assimilated by microorganisms, which is linearly correlated to bacterial re-growth in drinking water in some regions. The conventional MAP bioassay for drinking water was originally developed by Markku based on the growth potential of Pseudomonas fluorescens P17 (P17). However, the bioassay bears some demerits, such as time-consuming and labor-intensive enumeration. For convenience, an alternative method based on a similar principle was developed to assess the content of MAP in drinking water, in which natural microbial consortium was used as inoculum instead of pure culture P17, cell number was counted using flow cytometry (FCM), and cultivation at 30 °C was adopted. Natural microbial consortium is able to efficiently utilize organic phosphorus and exhibit high sensitivity since more cells are produced per μg P utilized. FCM is a rapid method to count all bacteria growing in drinking water. With incubation temperature increasing up to 30 °C, there is a shorter test period (64 h), excellent sensitivity and better utilization efficiency for organic phosphorus. The results show that the developed bioassay is sensitive, time-saving and easily operated.

Drinking water quality and formation of biofilms in an office building during its first year of operation, a full scale study

Complex interactions existing between water distribution systems' materials and water can cause a reduction in water quality and unwanted changes in materials, aging or corrosion of materials and formation of biofilms on surfaces. Substances leaching from pipe materials and water fittings, as well as the microbiological quality of water and formation of biofilms were evaluated by applying a Living Lab theme i.e. a research in a real life setting using a full scale system during its first year of operation. The study site was a real office building with one part of the building lined with copper pipes, the other with cross-linked polyethylene (PEX) pipes thus enabling material comparison; also differences within the cold and hot water systems were analysed. It was found that operational conditions, such as flow conditions and temperature affected the amounts of metals leaching from the pipe network. In particular, brass components were considered to be a source of leaching; e. g. the lead concentration was highest during the first few weeks after the commissioning of the pipe network when the water was allowed to stagnate. Assimilable organic carbon (AOC) and microbially available phosphorus (MAP) were found to leach from PEX pipelines with minor effects on biomass of the biofilm. Cultivable and viable biomass (heterotrophic plate count (HPC), and adenosine triphosphate (ATP)) levels in biofilms were higher in the cold than in the hot water system whereas total microbial biomass (total cell count (DAPI)) was similar with both systems. The type of pipeline material was not found to greatly affect the microbial biomass or Alpha-, Beta- and Gammaproteobacteria profiles (16s rRNA gene copies) after the first one year of operation. Also microbiological quality of water was found to deteriorate due to stagnation.

A review research of assimilable organic carbon bioassay

AbstractAssimilable organic carbon (AOC) is one of the important parameters internationally recognized to assess the biostability of water. Studies at home and abroad on the AOC bioassay’s development are reviewed from three aspects, including the selection of bacterial species for the bioassay, the optimization of inoculation method and incubation condition of water samples, and the evolution of bacterial growth measurement. The relationships between MAP (microbially available phosphorus), BRP (bacterial regrowth potential), and AOC are compared from determination mechanism. Moreover, the new development trend of AOC bioassay is predicted.

Research on Drinking Water Biological Stability in Water Supply Network

The Assimilable Organic Carbon (AOC), Microbially Available Phosphorus (MAP), Heterotrophic Plate Count (HPC) and Biodegradable Dissolved Organic Carbon (BDOC) of eight sampling points were analyzed for studying the biological stability of drinking water in Jinan. Biological stability of drinking water can standard basically in Jinan city. There had a certain correlation between AOC and HPC. The AOC indicator was gradual increased from April to May and June to July. There may be related to the seasonal change of Yellow River. The control of AOC was an effective way to improve the water quality.

Study on Phosphorus and Bacterial Regrowth in Drinking Water

Phosphorus limitation on bacterial regrowth was studied in source water, water treatment process and water distribution system of J Water Supply Plant in T city, by modified AOC method and MAP analysis. Based on the study, the follows can be concluded: ① MAP(Microbially Available Phosphorus) concentration was higher in source water and water treatment process, which was 5～38µg PO43－-P/L. However in water distribution, MAP concentration was lower, which was less than 5µg PO43--P/L. ②Coagulation and sedimentation can remove MAP efficiently. 31%～68% of MAP can be removed in these process. ③ In source water and water treatment process, there was no evident difference between AOCpotential, AOCp and AOCnative. So assimilable organic carbon (AOC) was the most important factor of bacterial regrowth. In water distribution system, the concentration of AOCpotential and AOCp were 2～8.7 times of the concentration of AOCnative. So phosphorus limited bacterial regrowth.

Phosphorus in Drinking Water and it's Removal in Conventional Treatment Process

Chemical forms of phosphorus in source and treated drinking water were studied in this paper. Removal of total phosphorus (TP) and microbially available phosphorus (MAP) by conventional treatment process of drinking water was examined. The results showed that particulate phosphorus constituted of most TP in source water. Content of total soluble phosphate (TSP) was about 30% of TP. Soluble reactive phosphate (SRP) can be measured in a few months during a year and its content was very low. Content of MAP was higher than content of TSP in source water, which showed that microbe can also use particle phosphorus. Ratio of TSP to TP increased evidently in treated water. This demonstrated that removal of TSP was more difficult than particulate phosphorus in conventional treatment process for drinking water. Removal of TP and MAP in conventional treatment process of drinking water was effective, with averaged removal efficiency of 66% and 69%, respectively. Coagulation-sedimentation and filtration removed TP efficiently. Enhanced coagulation may increases removal efficiency of MAP. Lower content of MAP can control biostability of drinking water.

Phosphorus limitation in nitrifying groundwater filters

Phosphorus limitation has been demonstrated for heterotrophic growth in groundwater, in drinking water production and distribution systems, and for nitrification of surface water treatment at low temperatures. In this study, phosphorus limitation was tested, in the Netherlands, for nitrification of anaerobic groundwater rich in iron, ammonium and orthophosphate. The bioassay method developed by Lehtola et al. (1999) was adapted to determine the microbially available phosphorus (MAP) for nitrification. In standardized batch experiments with an enriched mixed culture inoculum, the formation of nitrite and nitrate and ATP and the growth of ammonia-oxidizing bacteria (AOB; as indicated by qPCR targeting the amoA-coding gene) were determined for MAP concentrations between 0 and 100 μg PO 4–P L −1. The nitrification and microbial growth rates were limited at under 100 μg PO 4–P L −1 and virtually stopped at under 10 μg PO 4–P L −1. In the range between 10 and 50 μg PO 4–P L −1, a linear relationship was found between MAP and the maximum nitrification rate. AOB cell growth and ATP formation were proportional to the total ammonia oxidized. Contrary to Lehtola et al. (1999), biological growth was very slow for MAP concentrations less than 25 μg PO 4–P L −1. No full conversion nor maximum cell numbers were reached within 19 days. In full-scale groundwater filters, most of the orthophosphate was removed alongside with iron. The remaining orthophosphate appeared to have only limited availability for microbial growth and activity. In some groundwater filters, nitrification was almost totally prevented by limitation of MAP. In batch experiments with filtrate water from these filters, the nitrification process could be effectively stimulated by adding phosphoric acid.

Affect of Assimilable Organic Carbon (AOC) and Phosphorus to Heterotrophic Microbial Growth in Drinking Water Distribution System

The content of assimilable organic carbon (AOC) has been proposed to control the growth of heterotrophic microbe in drinking water distribution systme. However, recent results have shown that there are regions where it is predominantly phosphorus which determines the extent of microbial growth in drinking water. The growth of bacteria was studied in a drinking water distribution system where the content of AOC was high (40.84- 551.35 μg acetate-C/L) and the content of Microbially Available Phosphorus (MAP) was also high (0.69-8.01 μg PO43--P/L). It was AOC other than phosphorus that controlled the growth of bacteria in the drinking water distribution system. Comparably obvious linear relationship was found between the maximum HPC and the maximum content of AOC of the distribution system. Removal of organic matters is ideal approach to control water quality of the drinking water distribution system.

Biological Stability of Drinking Water in an Eastern China City

In this study, the indicators assimilable organic carbon (AOC), dissolved organic carbon (DOC), heterotrophic plate counts (HPC) and microbially available phosphorus (MAP) were measured to evaluate the biological stability of drinking water in Jinan, an east China city, which uses different water sources in its distribution system. The results were shown that the concentration of AOC below 50μg ac-C•L-1 covered the detection of 58% sampling points in the city distribution systems. The difference of source water exercised a great influence to the concentration of AOC. The lower heterotrophic colony counts were detected when the AOC values were higher, and vice versa. The value of AOC/DOC showed its irregularity. MAP was negatively correlated with the AOC. Higher values of AOC and HPC were detected in pumping water than that in pipe water, while values of MAP were equivalent to each othe

Effects of Total Phosphorus (TP) and Microbially Available Phosphorus (MAP) on Bacterial Regrowth in Drinking Water Distribution System

Changes of total phosphorus (TP) and microbially available phosphorus (MAP) in the drinking water distribution system and its’ effects on bacterial regrowth were investigated in a city for environment engineering. The content of TP was 2.93∼21.66ug/L and the content of MAP was 0.69-8.01 ugPO43”-P/L in the network. They decreased a little with the extend of hydraulic retention time. They also increased in some sampling point by cooperation of suspended bacteriam, biofilm and granule in the drinking water distribution system. Although an initial conclusion that phosphorus was a factor influencing the growth of bacteria in some sampling points by comparison of AOCpotential, AOCP and AOCnative had been deduced. Phosphorus was not the key factor that control bacterial regrowth in whole network because of high content of TP and MAP.

Evaluating the potential of biofilm control in water supply systems by removal of phosphorus from drinking water

Effect of microbially available phosphorus (MAP) on biofilm development in drinking water systems was investigated at the pilot-scale experiments over 3 years. Completely mixed biofilm reactors Propella (water detention time 24 h, flow rate 0.25 m s(-1), PVC pipe coupons) were used as water distribution network models. Four experimental runs were carried out with water containing different levels of phosphorus which was limiting nutrient for bacterial growth. Positive correlation between MAP in the inlet water and heterotrophic plate count (correlation coefficient 0.95) in biofilm, as well as for the total bacteria number (correlation coefficient 0.71), was observed. However, our experiments showed that removal of phosphorus down to very low levels (below detection limits of chemical method and MAP < 1 microg L(-1) was not an efficient strategy to eliminate bacterial regrowth and biofilm formation (< 51,00,000 cells/cm2) in drinking water supply systems.

Variation of dissolved organic matter and microbial regrowth potential through drinking water treatment processes

We investigated how various water treatment processes affect AOC (assimilable organic carbon) and MAP (microbially available phosphorus), which nutrient limits microbial growth between organic carbon and phosphorus, and what extent AOC is related to the MW fractions of NOM for raw waters of the Han River and process waters of two water treatment plants in Korea. In view of our results so far achieved, a significant difference was observed between MAP and MAP-P (potential MAP), while little difference was observed between AOC and AOC-P (potential AOC) for raw and pre-chlorinated waters, suggesting that organic carbon limits microbial growth instead of phosphorus. Conventional treatment processes poorly removed AOC-P (42.8%), since the AOC, which was mainly related to the small-molecular DOC, was hardly removed by conventional processes. Oxidants such as chlorine and ozone increased both of the AOC (AOC-P) and MAP (MAP-P), particularly ozone having the stronger oxidation power resulted in a larger increase. However, BAC and GAC removed AOC to less than 60 μg/L which meets the level for biological stability.

Investigation of microbially available phosphorus (MAP) in flemish drinking water

Several researchers have reported phosphorus growth limitations of heterotrophic bacteria instead of main energy source—organic carbon. Usually this phenomenon was noticed in waters with high organic carbon content, where phosphorus concentration was deficient to maintain the growth on level suggested by high organic carbon amount. We analysed the microbially available phosphorus (MAP) and assimilable organic carbon (AOC) in several drinking waters in Flanders, Belgium. Our aim was the investigation whether organic carbon or phosphorus is the restricting nutrient in specific water and determination of the impact of some treatment processes on MAP content. We obtained a wide range of MAP concentrations being from 0.3 to 15.2 μg P-PO 4/l in finished drinking water. In a treatment unit applying ozone, MAP was found to be the nutrient that limits bacterial growth instead of organic carbon. Moreover, ozone caused slight MAP decrease. Granular activated carbon (GAC) filtration was able to diminish further the MAP content significantly but not below a certain level. The biofilm monitor supplied with the MAP-limited water resulted in significantly lower biofilm formation rate (BFR) value than the same installation fed with AOC-limited water.

Formation of biofilms in drinking water distribution networks, a case study in two cities in Finland and Latvia

The formation of biofilms in drinking water distribution networks is a significant technical, aesthetic and hygienic problem. In this study, the effects of assimilable organic carbon, microbially available phosphorus (MAP), residual chlorine, temperature and corrosion products on the formation of biofilms were studied in two full-scale water supply systems in Finland and Latvia. Biofilm collectors consisting of polyvinyl chloride pipes were installed in several waterworks and distribution networks, which were supplied with chemically precipitated surface waters and groundwater from different sources. During a 1-year study, the biofilm density was measured by heterotrophic plate counts on R2A-agar, acridine orange direct counting and ATP-analyses. A moderate level of residual chlorine decreased biofilm density, whereas an increase of MAP in water and accumulated cast iron corrosion products significantly increased biofilm density. This work confirms, in a full-scale distribution system in Finland and Latvia, our earlier in vitro finding that biofilm formation is affected by the availability of phosphorus in drinking water.

Changes in content of microbially available phosphorus, assimilable organic carbon and microbial growth potential during drinking water treatment processes

There are regions where microbial growth in drinking water is limited by phosphorus instead of organic carbon. In phosphorus limited waters small changes in phosphorus concentration significantly affect microbial growth. We studied how water treatment processes in waterworks affect the availability of microbial nutrients and microbial growth potential in drinking water. The nutrients studied were assimilable organic carbon (AOC potential) and microbially available phosphorus (MAP) which both were quantified by bioassays. Chemical coagulation, commonly used in surfacewater works, effectively removed AOC potential and MAP. In contrast to activated carbon filtration, ozonation increased the concentrations of AOC potential and MAP, and also microbial growth potential. In most of the drinking waters, microbial growth was limited by phosphorus, and microbial growth potential correlated with the MAP concentration. Microbial growth potential was lowest in drinking waters produced from surface waters with efficient treatment technique and highest in less treated ground waters.

Microbially available organic carbon, phosphorus, and microbial growth in ozonated drinking water

Ozonation is a disinfection technique commonly used in the treatment of drinking water. It destroys harmful microbes, but it also degrades organic matter in water, increasing the bioavailability of organic matter. Recently, it was found that not only organic carbon but also phosphorus can limit the microbial growth in drinking water, which contains high amount of organic matter. We used a bioassay to analyze whether ozone could also increase the microbially available phosphorus (MAP) in drinking water, and whether MAP in ozone-treated water was associated with the growth of heterotrophic microbes. We found that both assimilable organic carbon and MAP concentrations were increased by ozone treatment. In ozonated water, microbial growth was mainly limited by phosphorus, and even minor changes in MAP concentration dramatically increased the growth potential of heterotrophic microbes. In this study, ozonation increased the MAP by 0.08–0.73 μg P/l, resulting in an increase of 80,000–730,000 CFU/ml in water samples. In contrast to MAP, the content of assimilable organic carbon (AOC potential) did not correlate with microbial growth. The results show that in water treatment not only AOC potential but also MAP should be considered as an important factor that can limit microbial growth in drinking water.