Impact of temperature and biomass augmentation on biosulfur-driven autotrophic denitrification in membrane bioreactors treating real nitrate-contaminated groundwater.

Nitrate (NO3-) contamination of groundwater is a major health concern worldwide as it can lead to serious illnesses such as methemoglobinemia and cancer. Autotrophic denitrification is a smart approach for treating groundwater, being typically organic-deficient. Lately, biogenic sulfur (S0bio) has emerged as a sustainable, free, and high-efficiency substrate to fuel membrane bioreactors (MBRs) treating contaminated groundwater. However, the effects of moderate temperature and biomass concentration on the performance and fouling of the S0bio-fed MBR were not investigated previously. This study shows that biomass levels of ~1 g MLVSS/L limit membrane fouling but also denitrification efficiency. Biomass augmentation up to 3 g MLVSS/L enhanced denitrification but worsened fouling due to increase of extracellular polymeric substance (EPS) levels in the bulk liquid. Temperature decrease from 30 °C to 20 °C halved denitrification efficiency, which could be partially recovered through bioaugmentation. The mechanisms affected by temperature decrease, practical applications, and future research needs were discussed.

Removal of fluoride from contaminated ground water using raw and modified bauxite.

Endemic fluorosis affects millions of people worldwide. Fluorosis arises from the consumption of fluorine (F) contaminated water and was observed also in some parts of Turkey with volcanic rocks and geothermal resources. In the present study the removal of F from drinking water by raw and modified bauxite at the laboratory scale was investigated using a batch mode. Modified bauxite was prepared by using Na and Mg incorporated (B-Na, B-Mg) bauxite and calcination of Mg incorporated bauxite at 500°C (B-Mg-500). The equilibration time for F between bauxite and water was identified to be 3 h. Adsorption of F increased with increasing adsorbent dose. Moreover, F adsorption isotherms fitted well with the Freundlich model. Low F adsorption was obtained onto the raw and incorporated bauxite. In contrast, maximum F adsorption was found for B-Mg-500, with Kf value of 0.247. This observation may be explained by the meaningfully stabilized and elevated number of positively charged sites in B-Mg-500.

Assessing the endosulfan contamination in an unconfined aquifer.

Groundwater samples were analyzed in order to elucidate the fate of endosulfan in the soil and its release mechanism into water of an unconfined aquifer. Residual alfa endosulfan was determined in all the wells; however, beta endosulfan was below 0.001 µg/L. Maximum adsorption rates of alfa and beta endosulfan were 91%-86% on the topsoil; 87%-91% on the subsoil, respectively. About 13%-23% desorption rate on the topsoil and subsoil exhibited the probability of endosulfan movement in the soil. The study showed that a hydrophobic-moderately persistent pesticide can reach to groundwater despite the high clay content of soil.

Effect of high sulfate concentration on the corrosivity: a case study from groundwater in Harran Plain, Turkey.

Corrosion, which tends to increase the concentrations of certain metals in tap water, is one of the most important water quality problems as it can affect public health and public acceptance of water supply and the cost of providing safe water. In this context, this study aimed at investigating the scale formation tendency or corrosivity of groundwater in the semi-arid Harran Plain. The degree of scale formation tendency/corrosivity of water was determined considering pHs, Langelier Index, and Ryznar Index of groundwater samples. Except for well no.4, which is close to a local hot spring, all the wells had corrosive characteristics. The amount of CO(2) from the soil zone respiration and high sulfate concentration in the wells are important factors affecting corrosiveness. Results showed that precipitation, excessive irrigation, and change in groundwater level caused seasonal variation in corrosive characteristics.

Sorption of alpha and beta hydrophobic endosulfan in a Vertisol from southeast region of Turkey.

Endosulfan has been applied to control numerous insects in a variety of food and non-food crops. Limited information is available on dynamics of this pesticide in the soil. The objective of this research was to determine the adsorption-desorption behavior of the alpha (alpha) and beta (beta) endosulfan in a Vertisol from the southeast region of Turkey, where cotton is the main crop in the large irrigated lowlands. The alpha and beta endosulfan were adsorbed considerably and Freundlich adsorption-desorption isotherms fitted the alpha and beta endosulfan data (R(2)>0.98). Freundlich adsorption coefficients (K(f)) for the alpha endosulfan ranged between 21.63 and 16.33 while for the beta endosulfan they were between 14.01 and 17.98 for the Ap and Bw2 horizons. The difference of K(f) values of alpha and beta endosulfan for two horizons were explained with the slight difference in the amount of organic matter and clay, but considerable difference in Fe contents of the two horizons. Alpha and beta endosulfan K(fd) values were 118.03 and 45.81 for the Ap and 48.08 and 68.71 for the Bw2 horizons. Higher adsorption and desorption behavior of the endosulfan isomers for the same horizon was attributed to poor physical bonding between the endosulfan molecule and the surfaces of fundamental soil particles. This fact is thought to increase the effective use of endosulfan in agriculture with a possibility of its movement to the surface and groundwater in the Vertisol studied.