Algal removal from cyanobacteria-rich waters by preoxidation-assisted coagulation–flotation: Effect of algogenic organic matter release on algal removal and trihalomethane formation

The cyanobacteria-bloom in raw waters frequently causes an unpredictable chemical dosing of preoxidation and coagulation for an effective removal of algal cells in water treatment plants. This study investigated the effects of preoxidation with NaOCl and ClO_2 on the coagulation-flotation effectiveness in the removal of two commonly blooming cyanobacteria species, Microcystis aeruginosa(MA) and Cylindrospermopsis raciborskii(CR), and their corresponding trihalomethane(THM) formation potential. The results showed that dual dosing with NaOCl plus ClO_2 was more effective in enhancing the deformation of cyanobacterial cells compared to single dosing with Na OCl, especially for CR-rich water.Both preoxidation approaches for CR-rich water effectively reduced the CR cell count with less remained dissolved organic carbon(DOC), which benefited subsequent coagulation–flotation. However, preoxidation led to an adverse release of algogenic organic matter(AOM) in the case of MA-rich water. The release of AOM resulted in a poor removal in MA cells and a large amount of THM formation after oxidation-assisted coagulation-flotation process. The reduction in THM formation potential of CR-rich waters is responsible for effective algae and DOC removal by alum coagulation. It is concluded that the species-specific characteristic of cyanobacteria and their AOM released during chlorination significantly influences the performance of coagulation–flotation for AOM removal and corresponding THM formation.     

Sludge-grown algae for culturing aquatic organisms: Part I. Algal growth in sludge extracts

This project is aimed at studying the feasibility of using sewage sludge to prepare culture media for microalgae (Chlorella-HKBU) and the use of the sludge-grown algae as a feed for some aquatic organisms. Part I of the project included results on preparing sludge extracts and their use on algal culture. By comparing two culturing techniques, aeration and shaking, it was noted that both lag and log phases were shortened in the aeration system. A subsequent experiment noted that algal growth subject to aeration rates of 1.0 and 1.5 liters/min had similar lag and log phases. In addition, both aeration rates had a significantly higher (P < 0.05) final cell density than that of 0.5 liters/min. A detailed study on the variation of growth conditions on the algal growth was done. The results indicated that pH values of all the cultures declined below 5 at day 12. The removal rates of ammonia N ranged from 62% to 70%. The sludge-grown algae contained a rather substantial amount of heavy metals (µg/g): Zn 289–581, Cu 443–682, Ni 310–963, Mn 96–126, Cr 25–118, and Fe 438–653. This implied that the rather high levels of heavy metals may impose adverse effects on higher trophic organisms.     

Organotin concentrations in three intertidal neogastropods from the coastal waters of Taiwan

This study was aimed to determine organotin concentrations in the muricids Thais clavigera, Thais tuberosa and Morula granulata on an island wide scale and to find an adequate bioindicator species for long-term monitoring purpose. Samples were collected from the coast of Taiwan and vicinity islands with organotin analysis by graphite furnace atomic absorption spectrophotometry. Because triphenyltin (TPT) could not be discriminated from tributyltin (TBT) by the extraction method, organotins were measured as TBT + TPT and total hexane extractable organotins. Severity of imposex in the muricid population samples expressed as relative penis size (RPS) indices were calculated and compared to determine a suitable bioindicator species. In T. clavigera, T. tuberosa and M. granulata, TBT + TPT were 17-157, 1-44 and 117-1343 ng Sn g(-1) dry wt, respectively. And total organotins varied in the range of 181 to 1125, 23 to 44 and 229 to 1402 ng Sn g(-1) dry wt, respectively. A positive correlation was found between TBT + TPT and total organotins in M. granulata (TBT + TPT = Total organotins x 1.01-110.79; R2=0.97; p<0.001). At the site of Dapaisha, total organotins in M. granulata was 10 times higher than in T. tuberosa (i.e. 242 versus 23 ng Sn g(-1) dry wt). No signs of imposex were found in T. tuberosa (a single site in two subsequent years) and in M. granulata (seven collection sites). The degree of imposex (RPS) of T. clavigera varied from 0.2 to 38.1%. The RPS indices from fishing harbors were not higher than from rocky shores and oyster culture sites. No correlation was found between RPS indices and concentrations of TBT + TPT or total organotins. M. granulata seemed to be insensitive to organotin pollution although organotins were also detected. Our results indicate that organotin pollution is wide spread in coastal waters of Taiwan and pollutants at least include butyltins and phenyltins. As a bioindicator species, T. clavigera is more appropriate than T. tuberosa and M. granulata to monitor organotin contamination.     

Influence of bacteria and diatoms in biofilms on metamorphosis of the marine slipper limpet <Emphasis Type="Italic">Crepidula onyx</Emphasis>

Larvae of the slipper limpet Crepidula onyx metamorphose in response to marine biofilms. In this study, we investigated how the percentage of larval metamorphosis in this species was affected by biofilms that differed in certain attributes. To manipulate bacterial and diatom cell densities and community composition, we developed biofilms in the laboratory (1) at different temperatures (16, 23 and 30°C) and salinities (20, 27 and 34‰), (2) with or without addition of antibiotics, and (3) in the light or in the dark. We also allowed biofilms to develop at three field sites with different prevailing environmental conditions so as to generate biofilms with different, but natural, attributes. Bacterial and diatom community composition in biofilms were determined using a DNA fingerprinting technique and microscopic examination, respectively. The effects of biofilms on metamorphosis were investigated in laboratory assays. The percentage of larval metamorphosis correlated with bacterial and diatom cell densities in only one of the three experiments conducted, but was substantially affected by differences in bacterial and diatom community composition in all three experiments. It also appears that metamorphosis of C. onyx depends on the simultaneous presence of both bacterial and diatom communities in biofilms.     

Green oysters caused by copper pollution on the Taiwan coast

The first case of green oysters (Crassostrea gigas) broke out along the Charting mariculture area of south-western Taiwan in January 1986. The green color was found to be due to high copper content in the oyster tissue. Since then, a long-term survey around this area shows that total dissolved copper ranges from 4.99 to 23.6 microg/liter and particulate copper ranges from 1.09 to 5.51 microg/liter in sea-water. The green oysters collected from the Erhjin Chi estuary on 26 January, 1989 gave the highest copper content, 4401+/-79 ppm dry wt. Other green oyster cases were occasionally observed in the Hsiangsan and Anpin mariculture areas. Meanwhile, an experiment of copper accumulation in oysters was conducted at three stations (south-western Taiwan) for up to 90 days. Multiple regression analysis indicates that the food pathway may predominate in copper accumulation by green oysters. This bioaccumulation experiment shows that the total uptake of copper per oyster is an exponential function of exposure time for the first 2 weeks with an accumulation rate of 214 ppm Cu/day and then levels off. The average values of concentration factors for oysters (about 5 x 10(5)) were very close to steady-state values under the natural conditions at each station.     

Dry deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in ambient air

The PCDD/Fs in the ambient air associated with concentration and dry deposition flux of four seasons were characterized in rural area. The mean PCDD/F concentrations were 0.342, 0.221, 0.675, 0.741 pg m(-3) and the mean I-TEQ values were 0.027, 0.016, 0.024, 0.063 pg m(-3) in spring, summer, fall and winter, respectively. Ambient air in winter was higher by a factor of 3.4 and 3.9 for PCDD/F concentration and I-TEQ, respectively, than in summer. The study area is located in a Tropical region. Hence, domestic heating is not found in this area and is not responsible for the elevated winter concentration in comparison to other studies. A smooth plate with a sharp leading edge that is pointed into the wind by a wind vane was used for measuring dry deposition flux of PCDD/Fs. Atmospheric dry deposition fluxes of total PCDD/Fs were 140, 116, 137, and 207 pg m(-2)day(-1) in spring, summer, fall, and winter, respectively, and averaged approximately 150 pg m(-2)day(-1). The total dry deposition flux was found to decrease as the temperature increased. Calculated dry deposition velocities of total PCDD/Fs were 0.45, 0.52, 0.32 and 0.39 cm s(-1) in spring, summer, fall, and winter, respectively, and averaged 0.42 cm s(-1).     

Contamination status of persistent organochlorines in human breast milk from Japan: recent levels and temporal trend

Contamination levels of persistent organochlorines (OCs) such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB), and chlordane compounds (CHLs) was examined in human breast milk collected during 2001-2004 from Fukuoka prefecture in Japan. The concentrations of OCs such as dioxins and related compounds, DDTs, CHLs and HCB in human breast milk from primiparae were comparable to or slightly higher than the data obtained during 1998, indicating that the levels of these contaminants in Japanese human breast milk have not decreased since 1998 and Japanese are continuously exposed to these chemicals, presumably via fish intake. In addition, OC levels in human breast milk from primiparae were significantly higher than those from multiparae, implying elimination of OCs via lactation. Furthermore, significant positive correlations were observed between levels of OCs in human breast milk and the age of primiparae. These results indicate that the mothers with higher age may transfer higher amounts of OCs to the first infant than to the infants born afterwards through breast-feeding, and hence the first born children might be at higher risk by OCs.     

Effects of nutrient concentration and litter cover on quantitative shoot parameters and belowground biomass of Zizania latifolia (L)

This study investigated the effect of nutrient concentration and litter cover on the development of quantitative shoot parameters and belowground biomass (BGB) production of Zizania latifolia. Zizania latifolia is a common emergent aquatic species in East Asia. Four treatments were done at the study site, and were observed between May 2003 and December 2005. The treatments are namely, high nutrient (HN) with litter cover (HNWL), high nutrient without litter cover (HNNL), low nutrient (LN) with litter cover (LNWL), and low nutrient without litter cover (LNNL). The quantitative shoot parameters and BGB had higher values for treatments with high nutrient (HN) compared to the low nutrient treatments (LN), independent of the presence of litter cover. Furthermore, the life span of the secondary shoots was also higher in HN treatments compared to LN treatments. The BGB productivity was higher in the HNNL treatment compared to the other treatments. The LNWL treatment showed the least developed quantitative shoot parameters, e.g. plant height, and the lowest BGB for Z. latifolia. It was generally observed that the combined effects of low nutrients and litter cover negatively affected shoot development and BGB production.     

Restoration of the Marine Ecological Environment Along the Charting Coast: Primary Productivity and Biomass Study

Since 1986, when green oysters occurred due to the copper and organic pollution in the Charting coastal area, the government banned all maricultural activity. It has been claimed that growing algae in a polluted environment may clean the water of pollutants and restore the marine ecosystem. to test this hypothesis, in the Charting coastal area a three-year programme (from August 1992 to July 1995) was carried out. the survey programme included environmental components such as salinity, temperature, pH, dissolved oxygen, biological oxygen demand (BOD), particulate organic carbon (POC), heavy metals and ecological indicators such as nutrients, chlorophyll-a, primary productivity. in the first year study, the environmental background data collected was used to select the suitable season and locations for growing large algae transferred from the laboratory to the field study area. Since September 1993, various species of large algae have been cultured. Although some of the growing algae were damaged by a typhoon in August 1994, the impact of the growing algae on the environmental conditions in the area has been monitored throughout. Elsewhere, we have reported that in the algae growing area higher dissolved oxygen with lower values of BOD and POC were found, and the concentrations of heavy metals in both water and sediments decreased. the purpose of this paper is to evaluate the possible impact of growing large algae on the ecological conditions in Charting coastal waters through the period from August 1983 to May 1995. As a result of the positive results obtained, large amounts of algae have again been cultured in the same area during the period from April 29 to May 25, 1995. We expect that inorganic and organic pollutants will be reduced by the algal growth, oyster mariculture will be restored and finally, the fishery resources potential will be increased.