Biodegradability and change of physical characteristics of particles during anaerobic digestion of domestic sewage

At the high-rate anaerobic treatment of domestic sewage, both biological and physical processes play an important role. Therefore, the anaerobic biodegradability of raw, paper-filtered and membrane-filtered sewage and black water has been investigated in batch experiments. Additionally, the effect of anaerobic digestion on physical characteristics, like particle size, surface tension and zeta-potential, of the present particles is studied. The biodegradability of domestic sewage and black water at 30 degrees C is almost similar (71-74%). Moreover, a high methanogenesis of the colloidal fraction in domestic sewage (86 +/- 3%) is achieved, showing that the low removal of colloidal particles in continuous high-rate anaerobic reactors is due to low physical removal rather than biodegradability. The lowest biodegradability is demonstrated for the dissolved fraction (62%). The results show that after anaerobic digestion the average radius of particles with diameter < 4.4 and < 0.45 microns increased for domestic sewage, while it decreased for black water. Part of the surface-active components in domestic sewage is not biodegraded during anaerobic batch digestion, as indicated by the development of the surface tension. The negative zeta-potential of all particles hardly changes during digestion, showing that colloidal interactions were not affected by anaerobic digestion.     

The Use of the Water Velvet Azolla Filiculoides in Wastewater Treatment

Azolla filiculoides is a free-floating water fern which fixes atmospheric nitrogen in association with the nitrogen-fixing blue-green alga Anabaena azollae. It is used for nutrient-removal purposes because it can grow under a wide range of environmental conditions.
This paper describes a series of experiments which was carried out in Alexandria, Egypt, to elucidate the performance of Azolla for the treatment of sewage and nutrient removal.     

Responses of the three test algae of the algal assay procedure: Bottle test

The Algal Assay Procedure (AAP): Bottle Test utilizes three test organisms which, under standardized culture conditions, give a range of responses to the physical and nutritional states of test waters. The test algae of the AAP are Selenastrum capricornutum, Microcystis aeruginosa and Anabaena flos-aquae. The responses of these organisms to light intensities and to micro- and macronutrients are described. Phosphate spikes as low as 1–2 μg P l⁻¹ are shown to give a measurable bioassay response in highly oligotrophic waters.The AAP test algae are used to assess the effects of nutrient enrichment with sewage in waters from a cross-section of U.S. lakes. Enrichment of oligotrophic waters with primary or secondary sewage effluent results in significant growth of the three algae, while sewage additions to eutrophic waters cause little or no significant increase in algal growth rate or maximum standing crop. The response of the AAP algae also indicate that nutrient removal by tertiary treatment greatly reduces the stimulatory properties of sewage. In the presence of tertiary sewage, growth rate and maximum standing crop of the three test organisms are near those of lake water controls.The AAP test protocol is shown to be useful in the determination of limiting nutrients and in the comparison of the algal growth potential of natural waters to that of defined media.     

Biological assessments of a mixture of endocrine disruptors at environmentally relevant concentrations in water following UV/H2O2 oxidation

Numerous studies have investigated degradation of individual endocrine disrupting compounds (EDCs) in lab or natural waters. However, natural variations in water matrices and mixtures of EDCs in the environment may confound analysis of the treatment efficiency. Because chemical based analytical methods cannot represent the combined or synergistic activities between water quality parameters and/or the EDC mixtures at environmentally relevant concentrations (microg L(-1)-ng L(-1)), bioanalytical assessments of residual estrogenic activity in treated water were used to evaluate the performance of the UV based advanced oxidation process for estrogenic contaminants in water. Four EDCs including estradiol (E(2)), ethinyl estradiol (EE(2)), bisphenol-A (BPA) and nonylphenol (NP) were spiked individually or as a mixture at mug L(-1)-ng L(-1) in laboratory or natural river water. The removal rates of estrogenic activity were quantitatively evaluated by in vitro yeast estrogen screen (YES) and in vivo Vitellogenin (VTG) assays with Japanese medaka fish (Oryzias latipes). UV in combination with 10 ppm H(2)O(2) as an oxidation process was capable of decreasing in vitro and in vivo estrogenic activity, however, in vivo estrogenic activity of the EDC mixture in natural water was not completely removed at UV fluence up to 2000 mJ cm(-2). The removal rates of in vitro estrogenic activity of the EDC mixtures were lower than those observed for single compounds, and slower in natural waters, likely due to lower steady-state concentrations of hydroxyl radicals (*OH) in the presence of *OH scavengers from the water matrix and EDC mixture.     

Pharmaceuticals and personal care products (PPCPs) in surface and treated waters of Louisiana,USA and Ontario,Canada

A newly developed analytical method was used to measure concentrations of nine pharmaceuticals and personal care products (PPCPs) in samples from two surface water bodies, a sewage treatment plant effluent and various stages of a drinking water treatment plant in Louisiana, USA, and from one surface water body, a drinking water treatment plant and a pilot plant in Ontario, Canada. The analytical method provides for simultaneous extraction and quantification of the following broad range of PPCPs and endocrine-disrupting chemicals: naproxen; ibuprofen; estrone; 17beta-estradiol; bisphenol A; clorophene; triclosan; fluoxetine; and clofibric acid. Naproxen was detected in Louisiana sewage treatment plant effluent at 81-106 ng/l and Louisiana and Ontario surface waters at 22-107 ng/l. Triclosan was detected in Louisiana sewage treatment plant effluent at 10-21 ng/l. Of the three surface waters sampled, clofibric acid was detected in Detroit River water at 103 ng/l, but not in Mississippi River or Lake Pontchartrain waters. None of the other target analytes were detected above their method detection limits. Based on results at various stages of treatment, conventional drinking-water treatment processes (coagulation, flocculation and sedimentation) plus continuous addition of powdered activated carbon at a dosage of 2 mg/l did not remove naproxen from Mississippi River waters. However, chlorination, ozonation and dual media filtration processes reduced the concentration of naproxen below detection in Mississippi River and Detroit River waters and reduced clofibric acid in Detroit River waters. Results of this study demonstrate that existing water treatment technologies can effectively remove certain PPCPs. In addition, our study demonstrates the importance of obtaining data on removal mechanisms and byproducts associated with PPCPs and other endocrine-disrupting chemicals in drinking water and sewage treatment processes.     

Stimulating hydrogenotrophic denitrification in simulated groundwater containing high dissolved oxygen and nitrate concentrations

In agricultural areas, nitrate (NO3-) is a common groundwater pollutant as a result of extensive fertilizer application. At elevated concentrations, NO3- consumption causes methemoglobinemia in infants and has been linked to several cancers; therefore, its removal from groundwater is important. The addition of hydrogen gas (H2) via gas-permeable membranes has been shown to stimulate denitrification in a laboratory-scale reactor. This research, using large columns packed with aquifer material to which a simulated groundwater was fed, was conducted to further identify the conditions required for the use of membrane-delivered H2 in situ. In this study, we show that this novel technology was capable of treating highly contaminated (25 mg/L NO3- -N) and oxygenated (5.5mg/L dissolved oxygen) water, but that nutrient addition and gas pressure adjustment was required. Complete NO3- reduction was possible without the accumulation of either NO2- or N2O when the H2 lumen pressure was increased to 17 psi and phosphate was added to the groundwater. The total organic carbon content of the effluent, 110 cm downgradient of H2 addition, did not increase. The results from these experiments demonstrate that this technology can be optimized to provide effective NO3- removal in even challenging field applications.     

Effect of agriculture on water quality of Lake Biwa tributaries, Japan

We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO(3), SO(4), NO(3), Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta(34)S values of SO(4) in the river water converged to 0+/-2 per thousand as the SO(4) concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO(3) concentration increased. In particular, both the delta(34)S values (0+/-2 per thousand) and the (87)Sr/(86)Sr ratios (0.7117+/-0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta(34)S values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable (87)Sr/(86)Sr in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO(3), owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO(3) and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries.     

人工介质去除源水中多氯联苯和多环芳烃研究

考察了人工介质富集微生物对W市源水中多氯联苯（PCBs）和多环芳烃（PAHs）的去除效果。试验结果表明，源水中存在较高浓度的PAHs；当介质的填充密度（介质与水的体积比）从15．6％增加到38％时，对PCBs和PAHs的去除率均有所增加；当HRT从3d增加到7d时，对PCBs和PAHs的去除率均没有明显提高。可见增加介质填充量有利于对PCBs和PAHs的去除，通过人工介质富集微生物对源水中的PCBs和PAHs有一定的去除效果，但出水PAHs浓度难以达到《城市供水水质标准》（CJ／T206-2005）的要求。     

Detergent phosphorus and algal growth

The total biomass of Chlorella pyrenoidosa (two strains) Chlamydomas reinhardtii. Euglena gracilis. Anabaena flos-aquae and Plectonenema boryanum was determined after the algae were grown in waters from Sylvan, Pleasant and Pidgeon Lakes (all in northeastern Indiana) that had been supplemented with 0.1, 1 or 10% sewage effluents (Indianapolis and Crawsfordsville, Indiana). Biomass was found not to be significantly decreased when the total phosphorus was reduced by alkaline treatment from 7.20-3.50 mg l⁻¹ (50 per cent reduction) for the Crawfordsville effluents. In another series of experiments Chlorella pyrenoidosa was grown in Sugar Creek water (west central Indiana) to which had been added 0.1. 1 or 10% sewage effluents that originated from a motel treatment system. Reactive sewage phosphorus was reduced from 15.4 to 7.44 mg l⁻¹ (57 per cent reduction) by supplying the motel with non-phosphorus cleaning products. No significant reduction in algal growth was observed. Only when effluents were advanced treated so that reactive phosphorus levels were below 1.2 mg l⁻¹ (92 per cent reduction) was algal growth significantly decreased.     

Sulphadimethoxine and Azolla filiculoides Lam.: a model for drug remediation

Plants can be an interesting tool for in situ remediation of drug contaminated waters. In a laboratory model Azolla filiculoides Lam., an aquatic fern known to absorb pollutants, has been exposed to an environmental persistent antibiotic commonly used in intensive farming, sulphadimethoxine (S), to test its bioremediation capability. In a 5 week experiment, plants were cultivated outdoor at four drug concentrations (50, 150, 300 and 450 mg l(-1)) in N-free mineral medium. Drug affects growth rate (as biomass yield per week), N2-fixation, heterocyst frequency, but plants are able to survive. Notwithstanding, at all concentrations tested drug was actively removed from the medium and the accumulation in the biomass is in order of magnitude up to mg g(-1) plant dry weight (1000 ppm). Drug uptake and degradation rates increase with S concentrations in the culture medium. The efficacy of the model was very high. These results demonstrated that Azolla can be taken into consideration as a tool for sulphonamides environmental monitoring and decontamination.     

潜流式人工湿地消纳城市污水厂尾水微生物特性及机制

为揭示潜流式人工湿地消纳城市污水厂尾水微生物特性及机制,以位于常州市城北污水处理厂内的潜流式人工湿地消纳城市污水厂尾水旁路试验系统中的植物根系、湿地填料及湿地土壤中微生物为研究对象,通过镜检、脲酶、磷脂脂肪酸(PLFA)等分析手段对其进行相关研究。结果表明,植物根系、填料中含有团藻等菌胶团和轮虫、变形虫等原生动物,团藻等菌胶团通过自身新陈代谢及光合作用,利用尾水中N、P进行生物代谢,去除低碳源条件下尾水中的N、P等。湿地脲酶平均含量(N)约为22.43mg/g,其活性与TN的去除呈线性相关,活性越高,TN去除率越高。消纳城市污水厂尾水湿地填料中饱和脂肪酸(PLFA)含量为99.30%,不饱和脂肪酸含量仅为0.70%,这与潜流式人工湿地处理城市污水中的PLFA含量有很大差别(分别为76.97%、23.03%)。以脂肪酸生物标记量为指标,显示湿地填料中形成了以好养细菌为优势种群的微生物生态结构。团藻、好氧微生物是低碳源尾水中TN等污染物去除的主要载体微生物。     

A novel in situ technology for the treatment of nitrate contaminated groundwater

A novel in situ membrane technology was developed to remove nitrate (NO3-) from groundwater. Membrane-fed hydrogen gas (H2) was used as an electron donor to stimulate denitrification. A flow-through reactor fit with six hollow-fiber membranes (surface area = 93 cm2) was designed to simulate groundwater flowing through an aquifer with a velocity of 0.3 m/day. This membrane technology supported excellent NO3- and nitrite (NO2-) removal once H2 and carbon limitations were corrected. The membrane module achieved a maximum H2 flux of 1.79 x 10(-2) mg H2/m2 s, which was sufficient to completely remove 16.4 mg/L NO3(-)-N from a synthetic groundwater with no NO2- accumulation. In addition, this model in situ treatment process produced a high quality water containing <0.5 mg/L total organic carbon.     

Distribution of linear alkylbenzenes (LABs) in riverine and coastal environments in South and Southeast Asia

This paper reports the result of sewage pollution monitoring conducted in South and Southeast Asia during 1998-2003 using linear alkylbenzenes (LABs) as molecular tracers of sewage contamination. Eighty-nine water samples collected from Malaysia, Vietnam, and Japan (Tokyo), and 161 surface sediment samples collected from Tokyo, Thailand, Malaysia, Philippines, Vietnam, Cambodia, Indonesia, and India were analyzed for alkylbenzenes. The concentration range of SigmaLABs in river water particles in Southeast Asia (<0.005-0.913 microg/L) was comparable to or higher than those found in Tokyo (<0.005-0.638 microg/L). I/E ratios (a ratio of internal to external isomers of LABs) in tropical Asian waters were close to the value of LABs in raw sewage ( approximately 1) and much lower than those in secondary effluents (3-5). This suggests that untreated or inadequately treated sewage is discharged into the water. SigmaLABs concentrations in sediments from South and Southeast Asia ranged from <0.002-42.6 microg/g-dry with the highest concentration occurring at several populous cities. Low I/E ratios of the sediments with high SigmaLABs concentrations suggest a heavy load of untreated sewage. Clearly in view of the current data and evidence of the implications of sewage pollution, this paper highlights the necessity of the continuation of water treatment system improvement in tropical Asia.     

Destruction of estrogenic activity in water using UV advanced oxidation

The transformation of the steroidal Endocrine Disrupting Compounds (EDCs), 17-beta-estradiol (E2) and 17-alpha-ethinyl estradiol (EE2) by direct UV photolysis and UV/H(2)O(2) advanced oxidation was studied from the perspective of the removal of estrogenic activity associated with the compounds. First, experiments were performed to link the oxidation of E2 and EE2 with subsequent reduction in estrogenic activity. No statistically significant difference between removal rates was observed, implying that the oxidation products of E2 and EE2 are not as estrogenic (measured by the Yeast Estrogen Screen (YES)) as the parent compounds. Utilizing the YES, 90% removal of estrogenic activity of E2 and EE2 at environmentally relevant concentrations ( approximately 3 microg L(-1)) was achieved using a combination of 5 mg L(-1) H(2)O(2) and a UV fluence of less than 350 mJ cm(-2). Thus, these compounds, when considered at environmentally relevant levels, are significantly degraded at much lower UV fluences than previously thought. A steady state OH radical model was used to predict oxidation of EE2 in laboratory and natural waters.     

Development of high-rate anaerobic ammonium-oxidizing (anammox) biofilm reactors

To promptly establish anaerobic ammonium oxidation (anammox) reactors, appropriate seeding sludge with high abundance and activity of anammox bacteria was selected by quantifying 16S rRNA gene copy numbers of anammox bacteria by real-time quantitative PCR (RTQ-PCR) and batch culture experiments. The selected sludge was then inoculated into up-flow fixed-bed biofilm column reactors with nonwoven fabric sheets as biomass carrier and the reactor performances were monitored over 1 year. The anammox reaction was observed within 50 days and a total nitrogen removal rate of 26.0 kg-Nm(-3)day(-1) was obtained after 247 days. To our knowledge, such a high rate has never been reported before. Hydraulic retention time (HRT) and influent NH(4)(+) to NO(2)(-) molar ratio could be important determinant factors for efficient nitrogen removal in this study. The higher nitrogen removal rate was obtained at the shorter HRT and higher influent NH(4)(+)/NO(2)(-) molar ratio. After anammox reactors were fully developed, the community structure, spatial organization and in situ activity of the anammox biofilms were analyzed by the combined use of a full-cycle of 16S rRNA approach and microelectrodes. In situ hybridization results revealed that the probe Amx820-hybridized anaerobic anammox bacteria were distributed throughout the biofilm (accounting for more than 70% of total bacteria). They were associated with Nitrosomonas-like aerobic ammonia-oxidizing bacteria (AAOB) in the surface biofilm. The anammox bacteria present in this study were distantly related to the Candidatus Brocadia anammoxidans with the sequence similarity of 95%. Microelectrode measurements showed that a high in situ anammox activity (i.e., simultaneous consumption of NH(4)(+) and NO(2)(-)) of 4.45 g-N of (NH(4)(+)+NO(2)(-))m(-2)day(-1) was detected in the upper 800 microm of the biofilm, which was consistent with the spatial distribution of anammox bacteria.     

Contributions of genotoxic precursors from tributary rivers and sewage effluents to the Yodo River in Japan

The cause of water pollution in the Yodo River was examined regarding the mutagenic potentials formed by chlorination of river waters and sewage effluents along the river. Mutagenicity of the extracts from chlorinated waters was measured by Ames test using S. typhimurium TA100 strain without metabolic activation. Mutagenic formation potentials of sewage effluents were 4-5 times higher than those of the three tributary river waters, the Kizu, Uji and Katsura Rivers. The contribution rates of the pollution loads from the three river waters and total of four sewage effluents to the Yodo River were revealed to be 10.2%, 42.2%, 22.1% and 25.5%, respectively. The rate of the sewage effluents occupied one-fourth and exceeded the rates of the Kizu and Katsura Rivers. The contribution rate of the two sewage effluents to the Katsura River was 46.3%. It could be confirmed that the relationship between COD and MFP in river waters and sewage effluents was very high with a correlation coefficient. These results indicated that the waters inflowing to the Yodo River were contaminated with numerous organic compounds, and the sewage effluents especially contribute to the formation of genotoxicity by the interaction between chlorine and organic components as genotoxic precursors in the purification plants.     

Effect of NOM and biofilm on the removal of Cryptosporidium parvum oocysts in rapid filters

Laboratory experiments were performed to evaluate the effects of biofilm and natural organic matter (NOM) on removal of Cryptosporidium parvum oocysts from water by filtration. The bench-scale rapid filters consisted of 2.54 cm ID x 30.5 cm polycarbonate plastic columns packed with 0.55 mm spherical glass beads to a depth of 25 cm and a porosity of 40%. Calcium chloride (0.01 M) served as the coagulant in most of the experiments. The oocyst removal efficiency decreased from 51 +/- 6% for a clean bed to 23 +/- 3% for the biofilm-coated bed and to 14 +/- 1% in the presence of 5 ppm of NOM. The oocyst removal for an experiment with a combination of biofilm-coated filter media and NOM was similar to that for the experiment with NOM alone (15 +/- 1%). The zeta potential values for the oocysts pre-equilibrated with NOM were significantly more negative than those obtained for untreated oocysts. This suggests that NOM enhanced the electrostatic repulsion between the oocysts and the negatively charged glass beads. Fortunately, use of alum as coagulant at a dosage sufficient to neutralize the surface charge of the NOM-coated oocysts resulted in a high removal efficiency (73 +/- 6%). Pre-equilibration of the oocysts with NOM also increased the hydrophobicity of the oocysts, but this was deemed to have a negligible effect on deposition onto the glass beads. The results of these experiments suggest that water treatment facilities treating source waters with moderate organic matter concentrations and/or employing biologically active filters have a greater potential for oocyst breakthrough and proper coagulation is critical for effective removal of oocysts in the filters.     

Elimination of COD, microorganisms and pharmaceuticals from sewage by trickling through sandy soil below leaking sewers

To simulate the filtration and/or degradation of trickling sewage from leaky sewers through the non-water-saturated underground, sewage was trickled through sand of 0.4-2mm from the Rhine valley in glass columns of 125 cm length. For the same sewage the chemical oxygen demand (COD) removal was almost independent of low or high trickling rates. The COD removal efficiency varied, however, from 67% to 79%, for sewage from rain and dry weather periods, respectively. The water content of the moist sand increased from initially 80 ml kg(-1) with increasing sewage trickling rates to 108 ml kg(-1) sand. It remained at 108 ml kg(-1) at higher trickling rates higher than 600 ml d(-1). Analyses of effluent of five consecutive 25-cm soil columns revealed that about 50% of the initial COD were filtrated off on top of the sand or degraded in the uppermost 25 cm at varying trickling rates. Another 6-12% of the COD were removed in the following 25-50 cm of sand, whereas almost no further COD removal was seen in the subsequent two or three 25-cm columns. The COD elimination during trickling of sewage through the segmented column (interrupted random flow) was slightly better than that in the non-segmented column. Total and faecal coliform bacteria decreased faster with increasing trickling depth than that of total aerobic or anaerobic bacteria. After a filter/degradation stretch of 125 cm elimination of all bacteria reached 96.2-99.9%. The sewage contained low concentrations of at least 10 different pharmaceuticals or X-ray media. During trickling of sewage through sand, elimination of these compounds by adsorption onto sand and/or biodegradation varied from a complete removal, e.g. Ibuprofen or Naproxen, to almost no removal for several X-ray contrast media. Some of the medicals were removed as effectively as during conventional sewage treatment.     

Occurrence of acidic pharmaceuticals in raw and treated sewages and in receiving waters

The occurrence of five acidic pharmaceuticals, ibuprofen, naproxen, ketoprofen, diclofenac and bezafibrate, in seven different sewage treatment plants (STP) and three receiving waters were determined. The analytical procedure included solid phase extraction, liquid chromatographic separation and detection by a triple-quadrupole mass spectrometer. The studied pharmaceuticals were found in all the STPs. The pattern of the occurrence of individual compounds was the same in every STP and matched the consumption figures reported in the literature. Ibuprofen is the most used pharmaceutical in Finland and was accordingly found to be the most abundant compound in the raw sewage. In the treatment processes, the highest removal rate was observed for ibuprofen and the lowest for diclofenac, 92%+/-8% and 26%+/-17%, respectively. Due to the incomplete removal in the STPs, the pharmaceuticals were found in rivers at the discharge points of the STP effluents. Downstream from the discharge points, the concentrations decreased significantly mainly due to dilution in the river water. The risk to the aquatic environment was estimated by a ratio of measured environmental concentration (MEC) and predicted no-effect concentration (PNEC). At the concentrations the compounds were found in the surface waters, they should not pose risk for the aquatic environment. However, at dry seasons and/or during malfunctions of STPs, ibuprofen could be associated with a risk in small river systems.     

Bioremediation efficiency in the removal of dissolved inorganic nutrients by the red seaweed, Porphyra yezoensis, cultivated in the open sea

The bioremediation capability and efficiency of large-scale Porphyra cultivation in the removal of inorganic nitrogen and phosphorus from open sea area were studied. The study took place in 2002-2004, in a 300 ha nori farm along the Lusi coast, Qidong County, Jiangsu Province, China, where the valuable rhodophyte seaweed Porphyra yezoensis has been extensively cultivated. Nutrient concentrations were significantly reduced by the seaweed cultivation. During the non-cultivation period of P. yezoensis, the concentrations of NH4-N, NO2-N, NO3-N and PO4-P were 43-61, 1-3, 33-44 and 1-3 micromol L(-1), respectively. Within the Porphyra cultivation area, the average nutrient concentrations during the Porphyra cultivation season were 20.5, 1.1, 27.9 and 0.96 micromol L(-1) for NH4-N, NO2-N, NO3-N and PO4-P, respectively, significantly lower than in the non-cultivation season (p<0.05). Compared with the control area, Porphyra farming resulted in the reduction of NH4-N, NO2-N, NO3-N and PO4-P by 50-94%, 42-91%, 21-38% and 42-67%, respectively. Nitrogen and phosphorus contents in dry Porphyra thalli harvested from the Lusi coast averaged 6.3% and 1.0%, respectively. There were significant monthly variations in tissue nitrogen content (p<0.05) but not in tissue phosphorus content (p>0.05). The highest tissue nitrogen content, 7.65% in dry wt, was found in December and the lowest value, 4.85%, in dry wt, in April. The annual biomass production of P. yezoensis was about 800 kg dry wt ha(-1) at the Lusi Coast in 2003-2004. An average of 14708.5 kg of tissue nitrogen and 2373.5 kg of tissue phosphorus in P. yezoensis biomass were harvested annually from 300 ha of cultivation from Lusi coastal water. These results indicated that Porphyra efficiently removed excess nutrient from nearshore eutrophic coastal areas. Therefore, large-scale cultivation of P. yezoensis could alleviate eutrophication in coastal waters economically.