Combining Coagulation and Electrocoagulation with UVA-LED Photo-Fenton to Improve the Efficiency and Reduce the Cost of Mature Landfill Leachate Treatment

This study focused on the reduction of the treatment cost of mature landfill leachate (LL) by enhancing the coagulation pre-treatment before a UVA-LED photo-Fenton process. A more efficient advanced coagulation pretreatment was designed by combining conventional coagulation (CC) and electro-coagulation (EC). Regardless of the order in which the two coagulations were applied, the combination achieved more than 73% color removal, 80% COD removal, and 27% SUVA removal. However, the coagulation order had a great influence on both final pH and total dissolved iron, which were key parameters for the UVA-LED photo-Fenton post-treatment. CC (pH = 5; 2 g L−1 of FeCl36H2O) followed by EC (pH = 5; 10 mA cm−2) resulted in a pH of 6.4 and 100 mg L−1 of dissolved iron, whereas EC (pH = 4; 10 mA cm−2) followed by CC (pH = 6; 1 g L−1 FeCl36H2O) led to a final pH of 3.4 and 210 mg L−1 dissolved iron. This last combination was therefore considered better for the posterior photo-Fenton treatment. Results at the best cost-efficient [H2O2]:COD ratio of 1.063 showed a high treatment efficiency, namely the removal of 99% of the color, 89% of the COD, and 60% of the SUVA. Conductivity was reduced by 17%, and biodegradability increased to BOD5:COD = 0.40. With this proposed treatment, a final COD of only 453 mg O2 L−1 was obtained at a treatment cost of EUR 3.42 kg COD−1.

Fractionation Analysis of Iron in Coastal Rivers to Yantai Sishili Bay with a Bismuth Microrods-Based Electrochemical Sensor

As an essential metal micronutrient, Fe plays an important role in the marine biogeochemical cycling process, and the bioavailability of Fe has a direct relationship with its fractions in water. The fractionation analysis of iron in main coastal rivers to Yantai Sishili Bay was achieved with an electrochemical sensor based on bismuth microrods (BiMRs). The sensor was characterized by scanning electron microscope and electrochemical methods, and the reliability of the sensor was verified by the determination of the standard samples. Different fractions of iron in coastal river waters, including total iron (TFe), total dissolved iron (TDFe) and particulate iron (PFe), have been determined by combining simple sample pretreatments and cathodic stripping voltammetry with the BiMRs-based sensor. The average concentrations of TFe in Guangdang River, Xin’an River and Yuniao River were 4.02, 3.66 and 4.42 μmol L−1, respectively. The main fractionation of iron in three rivers was PFe, which accounts for 84.46%, 87.56% and 92.34%, respectively. Furthermore, the relationships between iron concentration and tidal action, salinity, dissolved oxygen and other factors were also investigated.

Impact of the 2014 Major Baltic Inflow on benthic fluxes of ferrous iron and phosphate below the permanent halocline in the southern Baltic Sea

The impact of 2014 Major Baltic Inflow (MBI) on ferrous iron (FFe(II)) and phosphate (FPO43–) benthic fluxes was investigated. Sampling took place few months after the MBI, in August 2015, and over one year after the inflow, in February 2016. Materials were collected from three sites (depth of 106–108 m) located in the Gdańsk Deep. Total dissolved iron, Fe(II), phosphate, H2S and sulfate were analyzed in bottom and pore water. Benthic fluxes were estimated using Fick’s first law. All fluxes were directed from sediment. FFe(II) ranged from 0.31 × 10–2 to 1.25 × 10–2 μmol m–2 hr–1 and FPO43– from 1.53 to 2.70 μmol m–2 hr–1. At the deepest site, FPO43– was similar in both seasons, while at two other sites fluxes in August 2015 were 40–50% smaller than in February 2016. The increase in bottom water oxygen after the MBI enhanced Fe(oxyhydr)oxides formation. As a consequence, bottom and pore water concentrations of Fe(II) and FFe(II), decreased. Adsorption of phosphate onto Fe(oxyhydr)oxides resulted in binding of P in surface sediment and lower FPO43– in August 2015. This was particularly evident at the shallowest site. The reductive dissolution of Fe(oxyhydr)oxides and desorption of P during the subsequent months resulted in higher FPO43– in February 2016.

CLASSIFICATION AND ZONING OF WATER QUALITY FOR THREE MAIN RIVERS IN BINH TRI THIEN REGION (CENTRAL VIETNAM) BASED ON WATER QUALITY INDEX

Huong, Thach Han and Kien Giang rivers are the important surface water sources in Thua ThienHue, Quang Tri and Quang Binh provinces, respectively (in Central Vietnam). The river water samples were taken monthly (from June 2001 to May 2002 for Kien Giang river and from January to December of 2004 for Thach Han and Huong rivers) at selected sites. The temperature, pH, conductivity (EC), salinity, turbidity (TUR), DO, COD, BOD5, nitrate, ammonia, phosphate, total solids (TS), hardness, total dissolved iron, total coliform (TC), fecal coliform (FC) and sodium adsorption ratio (SAR) of water samples were analyzed. Water quality index developed by Bhargava (Bhargava-WQI) was modified and applied to assess water quality of the above mentioned rivers. Based on Bhargava-WQI, the classification and zoning of the rivers for beneficial uses were carried out. The results obtained show that the water quality index can be used as an efficient tool for the water quality management and water pollution control of the rivers.

IRON AVAILABILITY BY COASTAL DIATOM CHAETOCEROS SP. IN THE SHIZUGAWA BAY, JAPAN

This study aimed to investigate the spatial distribution of dissolved iron from river to coastal waters and iron bioavailability for coastal phytoplankton. Dissolved iron concentrations and other water quality parameters (e.g., pH, concentrations of dissolved organic carbon and trace metals, etc.) were determined in the Shizugawa Bay and its adjacent rivers, northeast Japan. Coastal dominant diatom (Chaetoceros sp.) isolated from the bay was used for incubational assay to examine growth kinetics in a range of iron concentrations. As a result, total dissolved iron concentrations of inland waters (75 ± 80 nM) were substantially higher than those of coastal waters (7.2 ± 4.8 nM). Among inland waters, iron concentrations from anthropogenic waters were relatively higher than those for forested river waters. In the bay, relatively higher concentrations of iron were observed in the inner part. From the growth experiment, half-saturation constant of iron for the growth of Chaetoceros sp. was determined to be 1.8 - 3.5 nM. The observed dissolved iron concentrations combined with growth response indicate that growth of Chaetoceros sp. is in some cases limited by iron availability. However, this study generally suggests that, while dissolved iron concentration largely decreased from river to coastal waters, terrestrial iron inputs potentially including both natural and anthropogenic sources contribute sufficient growth and iron availability by Chaetoceros sp. in the Shizugawa Bay.

IRON AVAILABILITY BY COASTAL DIATOM CHAETOCEROS SP. IN THE SHIZUGAWA BAY, JAPAN

This study aimed to investigate the spatial distribution of dissolved iron from river to coastal waters and iron bioavailability for coastal phytoplankton. Dissolved iron concentrations and other water quality parameters (e.g., pH, concentrations of dissolved organic carbon and trace metals, etc.) were determined in the Shizugawa Bay and its adjacent rivers, northeast Japan. Coastal dominant diatom (Chaetoceros sp.) isolated from the bay was used for incubational assay to examine growth kinetics in a range of iron concentrations. As a result, total dissolved iron concentrations of inland waters (75 ± 80 nM) were substantially higher than those of coastal waters (7.2 ± 4.8 nM). Among inland waters, iron concentrations from anthropogenic waters were relatively higher than those for forested river waters. In the bay, relatively higher concentrations of iron were observed in the inner part. From the growth experiment, half-saturation constant of iron for the growth of Chaetoceros sp. was determined to be 1.8 - 3.5 nM. The observed dissolved iron concentrations combined with growth response indicate that growth of Chaetoceros sp. is in some cases limited by iron availability. However, this study generally suggests that, while dissolved iron concentration largely decreased from river to coastal waters, terrestrial iron inputs potentially including both natural and anthropogenic sources contribute sufficient growth and iron availability by Chaetoceros sp. in the Shizugawa Bay.