Waters Of Taiwan Research Articles

Estimating the inverse demand function for transferring agricultural water in Taiwan

Changing climate has increasingly exacerbated droughts and floods in Taiwan; therefore, it is important to understand the actual demand of transferring Taiwan’s agricultural water. This estimation model could help the water resource agencies to develop appropriate mechanisms for transferring agricultural water, as well as bargaining tools for water-related negotiations. In this study, an inverse demand function estimation model for transferring agricultural water was established, and the water usage statistics derived from the water charge agreements, covering the period from January 1989 to December 2006 and including drought and non-drought periods, regarding the charging of water management fees and water usage fees, was applied to the estimation model in our empirical research. The agreements were made between irrigation associations and water companies, industrial water users, and science and industrial parks, for the purposes of strengthening irrigation management, building usage, and disposal of remaining water. The empirical research was conducted to estimate the demand for transferring agricultural water using double-log regression model for panel data, and analyzed with random effects models for regular conditions and drought periods. The results showed that the inverse demand function developed in this study was able to pass Largrange multiplier test, and adjusted R 2 for the regression were high, fitting the random effects model showing good compatibility with the sample selection. From the results, we can verify the estimation models to forecasting models. The significant results not only prove that the model could provide important market information for the commercialization of water resources, but water resource agencies could also make use of this important information to develop suitable mechanisms for transferring agricultural water, as well as bargaining tools for negotiation of water transactions.

Freaque waves during Typhoon Krosa

Abstract. This paper presents a subjective search for North Sea Draupner-like freaque waves from wave measurement data available in the northeastern coastal waters of Taiwan during Typhoon Krosa, October 2007. Not knowing what to expect, we found rather astonishingly that there were more Draupner-like freaque wave types during the build-up of the storm than we ever anticipated. As the conventional approach of defining freaque waves as Hmax/Hs>2 is ineffective to discern all the conspicuous cases we found, we also tentatively proposed two new indices based on different empirical wave grouping approaches which hopefully can be used for further development of effective indexing toward identifying freaque waves objectively.

Genetic Diversity and Differentiation of Gray Mullet (Mugil cephalus) in the Coastal Waters of Taiwan

From mid-December to late January, schools of mature gray mullet (Mugil cephalus) migrate southward along the coastal waters of China to Taiwan for spawning. It has been proposed that there is no genetic differentiation of gray mullet in the coastal waters of Taiwan. To test this hypothesis, complete cytochrome b (cyt b) DNA sequences of 98 Individuals of gray mullet, two Individuals of Liza macrolepis, and three individuals of L. affinis were amplified by polymerase chain reaction and sequenced. Phylogenetic trees reconstructed with the Bayesian, maximum likelihood, maximum parsimony, and neighbor-Joining methods all support the existence of three monophyletic groups (denoted as groups 1, 2, and 3), with net evolutionary divergences (p-distances) between groups ranging from 5.1% to 6.6%. To estimate the relative abundance of each group, a PCR-RFLP method was developed to examine 600 juveniles collected from October 2006 to March 2007. Groups 1, 2, and 3 comprised 85%, 3%, and 12% of the samples, respectively. Juveniles of groups 1 and 3 could be found as early as November, but Juveniles of group 2 were not found until February. Based on the dates of specimen collection and phylogenetic analyses, we propose that groups 1 and 2 are migratory populations from China and Japan, respectively, whereas group 3 is a resident population in Taiwan.

Use of a GIS-based hybrid artificial neural network to prioritize the order of pipe replacement in a water distribution network

A methodology based on the integration of a seismic-based artificial neural network (ANN) model and a geographic information system (GIS) to assess water leakage and to prioritize pipeline replacement is developed in this work. Qualified pipeline break-event data derived from the Taiwan Water Corporation Pipeline Leakage Repair Management System were analyzed. "Pipe diameter," "pipe material," and "the number of magnitude-3( + ) earthquakes" were employed as the input factors of ANN, while "the number of monthly breaks" was used for the prediction output. This study is the first attempt to manipulate earthquake data in the break-event ANN prediction model. Spatial distribution of the pipeline break-event data was analyzed and visualized by GIS. Through this, the users can swiftly figure out the hotspots of the leakage areas. A northeastern township in Taiwan, frequently affected by earthquakes, is chosen as the case study. Compared to the traditional processes for determining the priorities of pipeline replacement, the methodology developed is more effective and efficient. Likewise, the methodology can overcome the difficulty of prioritizing pipeline replacement even in situations where the break-event records are unavailable.

Phylogenetic relationships among fish of the subfamily Sparinae (Perciformes: Sparidae) in the coastal waters of Taiwan

Phylogenetic relationships among fish of the subfamily Sparinae (Perciformes: Sparidae) in the coastal waters of Taiwan

Phylogenetic relationships among fish of the subfamily Sparinae (Perciformes: Sparidae) in the coastal waters of Taiwan

The phylogenetic relationship of five species belonging to the subfamily Sparinae was investigated using starch-gel electrophoretic analysis of enzymes in skeletal muscle, heart, eye, liver, and sarcoplasmic protein in skeletal muscle. A total of 38 loci with 105 alleles coding for 25 enzymes and general protein were analysed and scored to calculate the proportion of polymorphic loci at the 95% level (P95), mean heterozygosity over loci (H), average number of alleles per locus (Na), and genetic distance (D). P95 values obtained ranged from 13.16 to 18.42%, H values ranged from 0.042 to 0.057, Na values ranged from 1.21 to 1.42, and an average D value of 0.305 (0.216–0.386) between congeneric species and 0.801 (0.614–0.896) between two consubfamilial genera, Acanthopagrus and Sparus, was found. A phenogram constructed on the basis of genetic data was similar to that based on morphometric characters at the genus level. However, discordance does exist among species of Acanthopagrus between the two sets of phenograms constructed. The results of this study support the niche-width-variation hypothesis. Zusammenfassung Phylogentische Beziehungen zwischen Fischarten aus der Unterfamilie Sparinae (Perciformes, Sparidae) aus den Kustengewassern Taiwans Die phylogentischen Verwandtschaftsbeziehungen zwischen funf Fischarten aus der Unterfamilie Sparinae wurden mit Hilfe der Starkegelelektrophorese untersucht und dabei Isozyme aus der Muskulatur, dem Herzen, dem Auge und der Leber und Proteine aus dem Sarkoplasma der Skelettmuskel verglichen. Insgesamt konnten 38 codierende Loci (davon 25 Enzym-Loci, der Rest allgemeine Protein-Loci) mit 105 Allelen erfast werden und daraus der Anteil polymorpher Loci (P95; entspricht dem 95%-Kriterium), der durchschnittliche Heterozygotiegrad (H), die durchschnittliche Zahl an Allelen pro Locus (Na) und genetische Distanzen (D) berechnet werden. Die Werte fur P95 schwankten zwischen 13.2 und 18.4%, die H-Werte zwischen 0.042 und 0.057, und die Na-Werte zwischen 1.21 und 1.42. Die Distanzen lagen zwischen Arten desselben Genus durchschnittlich bei 0.305 (0.216–0.386) und bei 0.801 (0.614–0.896) zwischen Arten unterschiedlicher Gattungen (Acanthopagrus und Sparus). Das aus den genetischen Daten konstruierte Phenogramm entsprach dem aus morphometrischen Charakteren abgeleiteten bezuglich der Gattungs-Beziehungen; Unterschiede zwischen genetischen und morphometrischen Daten zeigen sich jedoch bei den Arten des Genus Acanthopagrus. Die Ergebnisse dieser Arbeit unterstutzen auserdem auch die Hypothese der Variabilitatsabhangigkeit von der Nischen-Weite.

Prioritizing Pipe Replacement in a Water Distribution System Using a Seismic-Based Artificial Neural Network Model

This work focused on developing an approach for prioritizing the order of pipe replacement in a water distribution system (WDS) using a seismic-based artificial neural network (ANN). The qualified earthquake data obtained from the Taiwan Water Corporation Leakage Repair Management System (TWC-LRMS) were classified to build the model that was analyzed by both backward propagation network (BPN) and radial basis function network (RBFN). Pipe diameter, pipe material, and the number of monthly magnitude-3+ earthquakes provide the input parameters of the seismic-based ANN model for anticipating the priority of pipe replacement. The WDS of Yilan County, which frequently suffers from earthquakes in northeastern Taiwan, was used as the object of the case study. A comparison of the accuracy and reliability of the prediction model between BPN and RBFN demonstrated that RBFN outperformed BPN. The seismic-based ANN model developed in this work is streamlined for establishing a priority project of pipe replacement. The number of breaks predicted by the ANN model was close to the observed data. Furthermore, ANN has qualified as an effective technology for developing feasible pipe replacement priority in the domain of water leakage management.

Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

Dissolved and particulate 234Th activities in surface seawater were determined at 27 stations along the coastline of western Taiwan during 19–23 November 2004. Contrasting scavenging settings were observed between the northern and southern regimes of the nearshore water off western Taiwan, separated by the Cho-Shui River. The northern regime is characterized by a large quantity of suspended load contributed by northward transport of a suspension plume from the Cho-Shui River, while the southern regime, low in suspended load and high in chlorophyll concentration, is a system controlled by biological activity. A scavenging model that takes account of the physical transport was used to estimate the 234Th budget in order to estimate the scavenging and removal rates from the nearshore water. The scavenging and removal rates ranged from 21 to 127 dpm m−3d−1 and from 36 to 525 dpm m−3d−1, for dissolved and particulate 234Th, respectively. The removal fluxes of particulate organic carbon (POC) and particulate organic nitrogen (PON) were estimated by multiplying the particulate 234Th removal flux to the organic carbon/234Th and nitrogen/234Th ratios in suspended particles, which ranged from 4.5 to 275.2 mmol-C m−2d−1 and from 1.3 to 50.1 mmol-N m−2d−1, respectively. These fluxes resulted in residence times of 1∼20 days for the POC in the surface water of nearshore water off western Taiwan.

Occurrence of haloacetic acids (HAAs) and trihalomethanes (THMs) in drinking water of Taiwan.

In this study, water samples were collected from 86 water treatment plants for analysis of haloacetic acids (HAAs) and trihalomethanes (THMs) from February to March, 2007 and from July to August, 2007. Both seasonal and geographical variations of disinfection by-products (DBPs) in drinking water of Taiwan were presented. The results showed that the five HAA concentrations (HAA5) were 1.0-38.9 microg/L in the winter and 0.2-46.7 microg/L in the summer; and the total THMs were ND-99.4 microg/L in the winter and ND-133.2 microg/L in the summer. For samples taken from the main Taiwan island, dichloroacetic acid (29.4-31.7%) and trichloroacetic acid (25.3-27.6%) were the two major HAA species, and trichloromethane was the major THM species (49.9-62.2%) in finished water. For water treatment plants located on the offshore islands outside of Taiwan, high bromide concentration was found in raw water, and higher percentage of brominated THMs and HAAs were formed in the overall formation. A statistically significant (P < 0.005) logarithmic linear regression model was found to be useful to describe the correlations between TTHM and HAA5 or nine HAAs (HAA5 = 1.219 x TTHM (0.754), R(2) = 0.658; HAA9 = 1.824 x TTHM (0.735), R(2) = 0.678). No apparent difference was observed for DBPs concentrations between finished water and distribution samples in this study.

Nitrate in Drinking Water and Risk of Death From Pancreatic Cancer in Taiwan

The relationship between nitrate levels in drinking water and risk of pancreatic cancer development remains inconclusive. A matched case-control and nitrate ecology study was used to investigate the association between mortality attributed to pancreatic cancer and nitrate exposure from Taiwan's drinking water. All pancreatic cancer deaths of Taiwan residents from 2000 through 2006 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Data on nitrate-nitrogen (NO3–N) levels of drinking water throughout Taiwan were collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was assumed to be the source of the subject's nitrate exposure via drinking water. The adjusted odds ratios and confidence limits for pancreatic cancer death for those with high nitrate levels in their drinking water, as compared to the lowest tertile, were 1.03 (0.9–1.18) and 1.1 (0.96–1.27), respectively. The results of the present study show that there was no statistically significant association between the levels of nitrate in drinking water and increased risk of death from pancreatic cancer.

Temporal and Spatial Reproductive Patterns of Subtidal Brachyuran Crabs in Coastal Waters of Taiwan

The reproductive dynamics of subtidal brachyuran crabs in the coastal waters of Taiwan were studied. A total of 41 species of crabs was examined, each with at least one ovigerous individual, from seven sampling sites throughout the island. Differences in distribution range between the brooding and non-brooding populations of Charybdis bimaculata, Portunus argentatus, P. haanii, P. hastatoides, and P. pelagicus suggest that they use different types of habitat. The greater number of species recorded at the southern sampling locations indicates that most subtidal brachyuran crabs observed in the coastal waters of Taiwan favour warmer waters and fine sediment substrates as their breeding grounds. However, the brooding populations of several species (e.g., C. bimaculata, C. natator, Heikeajaponicus, Phalangipus hystrix, Portunus gracillimus, and Thalamita sima) were found both at deep and shallow sampling locations, suggesting these species may have a wider range of preferences with regard to water temperature and types of sediment. Four reproductive patterns were recognized: (1) limited to a single season, (2) stretching two or three consecutive seasons, (3) bi annual, and (4) year-round. Differences in peak reproductive times of C. bimaculata, P. argentatus, and P. haanii between deep and shallow sampling locations suggest the presence of reproductive

Age and growth estimates of the sharptail mola, Masturus lanceolatus, in waters of eastern Taiwan

The sharptail mola, Masturus lanceolatus, is one of the largest teleost fishes in the world, and can be found in warm temperate and tropical regions worldwide. The increase of sharptail mola catch in the eastern Taiwan in recent years stimulated a concern that increasing exploitation of this species might lead to a decline of the stock. However, biological information of this species is very limited. Hence, this study provides the first information on age and growth of this species in the waters off eastern Taiwan based on 265 specimens (105 females and 160 males) collected from January 2003 to November 2006 at the Nanfanao and Hualien fish markets, eastern Taiwan. The relationships between whole weight ( W) and standard length were expressed as: W = 9.98 × 10 −4 SL 2.45 ( n = 105, p < 0.01) for females, and W = 3.33 × 10 −4 SL 2.68 ( n = 160, p < 0.01) for males. Based on the MIR analysis, growth band pairs (including translucent and opaque bands) in vertebrae formed once a year and were counted up to 23 and 16 for females and males, respectively. Three growth functions, the von Bertalanffy (VBGF), Robertson, and Gompertz, were used to model the observed length at age data. The VBGF had the best fit and predicted an asymptotic length ( L ∞) = 262.5 cm SL, growth coefficient ( k) = 0.046 yr −1, age at zero length ( t 0) = −3.350 yr ( n = 80, p < 0.01) for females, and L ∞ = 231.0 cm SL, k = 0.059 yr −1, t 0 = −1.852 yr ( n = 135, p < 0.01) for males. The longevities were estimated to be 105 and 82 yr based on the VBGF for females and males, respectively.

Multi-objective Planning for Conjunctive Use of Surface and Subsurface Water Using Genetic Algorithm and Dynamics Programming

The consideration of fixed cost and time-varying operating cost associated with the simultaneous conjunctive use of surface and subsurface water should be treated as a multi-objective problem due to the conflicting characteristics of these two objectives. In order to solve this multi-objective problem, a novel approach is developed herein by integrating the multi-objective genetic algorithm (MOGA), constrained differential dynamic programming (CDDP) and the groundwater simulation model ISOQUAD. A MOGA is used to generate the various fixed costs of reservoirs’ scale, generate a pattern of pumping/recharge, and estimate the non-inferior solutions set. A groundwater simulation model ISOQUAD is directly embedded to handle the complex dynamic relationship between the groundwater level and the generated pumping/recharge pattern. The CDDP optimization model is then adopted to distribute the optimal releases among reservoirs provided that reservoir capacities are known. Finally, the effectiveness of our proposed integrated model is verified by solving a water resources planning problem for the conjunctive use of surface and subsurface water in southern Taiwan.

Population differentiation in the barnacle Chthamalus malayensis: postglacial colonization and recent connectivity across the Pacific and Indian Oceans

Chthamalus malayensis is a common intertidal acorn barnacle widely distributed in the Indo-West Pacific. Analysis of the mitochondrial cytochrome c oxidase subunit I (COI) sequences of samples from its distribution range revealed 3 genetically differentiated clades: the South China Sea, Indo-Malay and Taiwan clades. The clades have an allopatric distribution and differed by ~7.5 to 14% in COI. They also differed in zonation patterns and abundances within vertical ranges. The genetic and ecological differences suggest that the 3 clades probably represent distinct species. There were signatures of postglacial demographic expansion, yet the timing of expansion varied among clades, which is attributable to the differences in their geographical distributions. The Indian Ocean population of the Indo-Malay clade apparently attained its present range by postglacial re-colonization from the Pacific and, as a result, genetic differentiation among populations in the 2 oceans is low (ΦCT = -0.01, p = 0.49). There were differences in cohort structure between popula- tions in India and the Malay Peninsula. Together, this suggests a considerable level of contemporary gene flow over an evolutionary, but relatively restricted dispersal on an ecological time scale. Cohort structure also varied among Malaysia and Singapore, the South China Sea and Taiwan waters, indicating distinct larval supplies among the 3 clades, possibly determined by different ocean current systems. This physical dispersal of larvae interacts with local biological factors in determining the on-shore distribution and genetic structure of the barnacle populations. Our findings highlight the importance of combining ecological and genetic data to understand factors that mould biodiversity patterns.

Risk-based assessment of arsenic-affected aquacultural water in blackfoot disease hyperendemic areas

This work explored a risk-based arsenic (As) regulation in farmed pond water by ingesting tilapia (Oreochromis mossambicus) in blackfoot disease hyperendemic areas and discussed a rational As regulation in pond water. Monte Carlo analysis was used to propagate the parameter uncertainty and to assess probabilistically regulation risks. A dynamic scheme of groundwater management was proposed that curves of utilization ratios against As concentrations in groundwater were established based on the risk-based regulation. The 5th to 95th percentiles of risks range from 3.5 × 10−7 to 6.0 × 10−5 via ingesting the farmed tilapia under the current As regulation in farmed pond water in Taiwan, 50 μg/L. To compare to inorganic As regulation in drinking water, the current As regulation in farmed pond water does not pose a great threat to human health, but it is unsafe. Therefore, this study suggests that the regulation of As in farmed pond water is revised to be 25 μg/L.

Evaluation of biological stability and corrosion potential in drinking water distribution systems: a case study

The appearance of assimilable organic carbon (AOC), microbial regrowth, disinfection by-products (DBPs), and pipe corrosion in drinking water distribution systems are among those major safe drinking water issues in many countries. The water distribution system of Cheng-Ching Lake Water Treatment Plant (CCLWTP) was selected in this study to evaluate the: (1) fate and transport of AOC, DBPs [e.g., trihalomethanes (THMs), haloacetic acids (HAAs)], and other organic carbon indicators in the selected distribution system, (2) correlations between AOC (or DBPs) and major water quality parameters [e.g. dissolved oxygen (DO), free residual chlorine, and bacteria, and (3) causes and significance of corrosion problems of the water pipes in this system. In this study, seasonal water samples were collected from 13 representative locations in the distribution system for analyses of AOC, DBPs, and other water quality indicators. Results indicate that residual free chlorine concentrations in the distribution system met the drinking water standards (0.2 to 1 mg l(-1)) established by Taiwan Environmental Protection Administration (TEPA). Results show that AOC measurements correlated positively with total organic carbon (TOC) and UV-254 (an organic indicator) values in this system. Moreover, AOC concentrations at some locations were higher than the 50 microg acetate-C l(-1) standard established by Taiwan Water Company. This indicates that the microbial regrowth might be a potential water quality problem in this system. Higher DO measurements (>5.7 mg l(-1)) might cause the aerobic biodegradation of THMs and HAAs in the system, and thus, low THMs (<0.035 mg l(-1)) and HAAs (<0.019 mg l(-1)) concentrations were observed at all sampling locations. Results from the observed negative Langelier Saturation Index (LSI) values, higher Ryznar Stability Index (RSI) values, and high Fe3+ concentrations at some pipe-end locations indicate that highly oxidative and corrosive conditions occurred. This reveals that pipe replacement should be considered at these locations. These findings would be helpful in managing the water distribution system for maintaining a safe drinking water quality.

Comparison of the decapod communities in an anthropogenic impacted lagoon and its adjacent coastal waters

In this study, benthic decapods were sampled approximately for every three months between September 2000 and June 2002 in a heavily used subtropical lagoon and its vicinity waters in southwestern Taiwan. Seventeen shrimp species (dominated by Metapenaeus ensis and Penaeus semisulcatus) and 19 crab species (dominated by Thalamita crenata) were recorded within the lagoon, whereas a combined total of 32 shrimp species (mainly Metapenaeopsis barbata and M. palmensis) and 50 crab species (dominated by Portunus hastatoides) were recorded at 10, 20, 30, and 40-m depths outside the inlet–outlet of the lagoon. The decapod community in the lagoon varied little temporally, and was significantly different from those in the nearby waters. The results of this study document a decapod fauna in a lagoon subjected to decades of aquaculture activities and revealed that these activities benefited a distinct decapod assemblage, yet may have prevented the potential use of the lagoon by other species as a nursery or refuge. Aquaculture activities have since been prevented and dredging of the benthic sediments in the lagoon has been underway; thus the results of present study will provide a valuable and rare baseline data set to be used for future studies to determine how decapod communities shift in response to habitat change.

Associations between Arsenic in Drinking Water and Pterygium in Southwestern Taiwan

BackgroundPterygium is a fibrovascular growth of the bulbar conjunctiva and underlying subconjunctival tissue that may cause blindness. The mechanism of pterygium formation is not yet fully understood, but pterygium has some tumorlike features.ObjectivesThe objective of this study was to evaluate the association between arsenic exposure through drinking water and the occurrence of pterygium in southwestern Taiwan.MethodsWe recruited participants > 40 years of age from three villages in the arseniasis-endemic area in southwestern Taiwan (exposure villages) and four neighboring nonendemic villages (comparison villages). Each participant received an eye examination and a questionnaire interview. Photographs taken of both eyes were later graded by an ophthalmologist to determine pterygium status.ResultsWe included 223 participants from the exposure villages and 160 from the comparison villages. The prevalence of pterygium was higher in the exposure villages across all age groups in both sexes and increased with cumulative arsenic exposure. We found a significant association between cumulative arsenic exposure and the prevalence of pterygium. After adjusting for age, sex, working under sunlight, and working in sandy environments, we found that cumulative arsenic exposure of 0.1–15.0 mg/L-year and ≥ 15.1 mg/L-year were associated with increased risks of developing pterygium. The adjusted odds ratios were 2.04 [95% confidence interval (CI), 1.04–3.99] and 2.88 (95% CI, 1.42–5.83), respectively.ConclusionsChronic exposure to arsenic in drinking water was related to the occurrence of pterygium, and the association was still observed after adjusting for exposures to sunlight and sandy environments.

Molecular detection and prevalence of enterovirus within environmental water in Taiwan

To investigate the presence of enterovirus RNA in various samples of environmental water collected in Taiwan during 2004-2005, and to characterize the genotypes and distribution of the viruses identified in Taiwan. Total 131 environmental samples were screened using the reverse transcription polymerase chain reaction (RT-PCR) for the highly conserved 5'-nontranslated regions (5'-NTR). Among these enterovirus RNA-positive samples, 32, 15 and 6 of the samples were recovered from surface water, ground water and sewage water respectively. However, the total positive detection rate increased to 40.5% with the application of seminested PCR. Sequencing revealed that the majority of isolates belonged to the following genotypes: coxsackie A2 (35.8%), coxsackie A6 (13.2%) and enterovirus (EV)71 (11.3%); echovirus 11, porcine EV9 and coxsackie A16 isolates were also observed. This study confirms that the major epidemic genotypes of enterovirus are prevalent in the surface and ground water of Taiwan. This study is helpful in understanding the significance and epidemiology of the virus within and beyond the study area. Moreover, it was possible to predict the enterovirus genotype and evaluate possible correlations between water contamination and viral sequences found among clinical samples.

Operation of Fixed‐bed Bioreactor for Polluted Surface Water Treatment

Dissolved organic matters and ammonia nitrogen are serious contaminants of surface water in Taiwan. These contaminants can interfere with the water treatment process and cause biological instability in the finished water. One solution is to employ a biological treatment stage prior to the conventional water treatment process. A continuous flow biological filter packed with reticulated PU foam was used to remove ammonia nitrogen and organic materials before the conventional water treatment practice. The effect of its operation mode, namely, empty bed contact time (EBCT) and backwash, on the removal efficiencies of ammonia and organic matter was examined. The results suggested that ammonia nitrogen and organic nitrogen can be effectively removed by controlling the operation mode of the biological fixed bed. Efficient ammonia nitrogen removal was achieved upon the combination of the backwash mode with short EBCT or extended EBCT without the backwash. Efficient organic nitrogen and DOC removals were observed at short EBCT without the backwash. This study provides insights into the function of biofiltration, which benefits the design of a fixed‐bed bioreactor for the treatment of polluted surface water.