Performance of a high-rate membrane bioreactor for energy-efficient treatment of textile wastewater.

High-rate membrane bioreactors (MBR), where the wastewater undergoes partial oxidation due to the applied short sludge retention time (SRT) and hydraulic retention time (HRT) values, retain the majority of the organic substances in the sludge through growth and biological flocculation. Thus, a raw material source with a high biomethane production potential is created for the widespread use of circular economy or energy-neutral plants in wastewater treatment. While high-rate MBRs have been successfully employed for energy-efficient treatment of domestic wastewater, there is a lack of research specifically focused on textile wastewater. This study aimed to investigate the textile wastewater treatment and organic matter recovery performances of an aerobic MBR system containing a hollow fiber ultrafiltration membrane with a 0.04 µm pore diameter. The system was initially operated at short SRTs (5 and 3 d) and different SRT/HRT ratios (5, 10, and 20) and subsequently at high-rate conditions (SRT of 0.5-2 d and HRT of 1.2-9.6 h) which are believed to be the most limiting conditions tested for treatment of real textile wastewater. The results showed that chemical oxygen demand (COD) removal averaged 77% even at SRT of 0.5 d and HRT of 1.2 h. Slowly biodegradable substrates and soluble microbial products (SMP) accumulated within the MBR at SRT of 0.5 and 1 d, which resulted in decreased sludge filterability. The observed sludge yield (Yobs) exhibited a considerable increase when SRT was reduced from 5 to 1 d. On the other hand, the SRT/HRT ratio displayed a decisive effect on the energy requirement for aeration.

GIS based spatial pattern analysis: Children with Hepatitis A in Turkey.

This study aimed to provide an insight into the geographic distribution of Hepatitis A incidence considering their temporal distribution, spatial patterns, hot spots and clusters identification in three different age-group (0-4, 5-9 and 10-14) in Turkey. Province based tabular data, including monthly numbers of Hepatitis A cases in children, and the populations from 2001 to 2011 were used as the basic input of the study. Time series maps were created using Geographic Information Systems (GIS) to introduce the temporal changes in the morbidity rates of Hepatitis A. The spatial variation of Hepatitis A was measured using Moran's I at the global level and the local indicators of spatial associations (LISAs) Moran's I and Getis-Ord Gi *(d) in order to identify influential locations through clusters and hot spots detection of Hepatitis A cases. The morbidity rates in children under the age of 5 were found significantly lower than the other age-groups, whereas the age-group 5-9 revealed the highest morbidity rates in the study area. The morbidity of Hepatitis A was detected very high for the years 2001, and 2005-2007. The identification of the highly vulnerable provinces was conducted using local Moran's I and local Getis-Ord Gi *(d). The majority of clusters and hot spots were detected to be agglomerated in the Eastern Mediterranean and South-Eastern Anatolian Regions and Ceyhan, Asi and Southeast part of Firat-Dicle river basins in Turkey.

Fate and effect of xenobiotics on biodegradation processes: basis for respirometric appraisal.

The paper mainly focused on illustrating the merit of respirometric analysis in assessing the inhibitory/toxic impact of xenobiotics on substrate biodegradation. It also evaluated biodegradation characteristics of these chemicals at continuous exposure through acclimation ofthe microbial culture. The nature and role ofoxygen uptake rate (OUR) profiles were discussed in conjunction with appropriate modelling, which should incorporate dissolved oxygen as an indispensable component for respirometric evaluation. Emphasis was placed upon differentiating acute effects from chronic impact, which may be totally different as it involves biodegradation of the chemical due biomass acclimation. Three case studies, each involving OUR measurements and process modelling, were presented for this purpose. The first one related to the inhibitory action of pharmaceutical effluent when mixed with plain-settled tannery wastewater. The second investigated the fate of H-acid, a commercially important naphthalene sulfonate, which exerted no adverse effect on substrate biodegradation, while remaining intact before and after a long acclimation period. The third one involved 2,6-dihydroxybenzoic acid, a naturally occurring organic compound in olive oil wastewater, which became biodegradable after acclimation by the development ofa specific microbial biomass fraction, while it heavily inhibited substrate biodegradation at first exposure. Model evaluation of the experimental data could provide related information on process stoichiometry and kinetics in all studies.

A New Activated Sludge Model with Membrane Separation-Implications for Sewage and Textile Effluent.

A new model for the activated sludge process with membrane separation is presented, based on the effective filtration size. A new size threshold is imposed by the membrane module. The model structure requires a modified fractionation of the chemical oxygen demand and includes chemical oxygen demand fractions entrapped in the reactor or in the flocs as model components. This way, it offers an accurate mechanistic interpretation of microbial mechanisms taking place in membrane activated sludge systems. Denim processing wastewater was selected for model implementation, which emphasized the significance of entrapped fractions of soluble hydrolysable and soluble inert chemical oxygen demand responsible for better effluent quality, while underlining the shortcomings of existing activated sludge models prescribed for systems with conventional gravity settling. The model also introduced particle size distribution analysis as a new experimental instrument complementing respirometric assessments, for an accurate description of chemical oxygen demand fractions with different biodegradation characteristics in related model evaluations.

Model-based process analysis of partial nitrification efficiency under dynamic nitrogen loading.

In this study, the ammonia removal efficiency for high ammonia-containing wastewaters was evaluated via partial nitrification. A nitrifier biocommunity was first enriched in a fill-and-draw batch reactor with a specific ammonium oxidation rate of 0.1 mg NH(4) (-)-N/mg VSS.h. Partial nitrification was established in a chemostat at a hydraulic retention time (HRT) of 1.15 days, which was equal to the sludge retention time (SRT). The results showed that the critical HRT (SRT) was 1.0 day for the system. A maximum specific ammonium oxidation rate was achieved as 0.280 mg NH(4) (-)-N/mg VSS.h, which is 2.8-fold higher than that obtained in the fill-and-draw reactor, indicating that more adaptive and highly active ammonium oxidizers were enriched in the chemostat. Dynamic modeling of partial nitrification showed that the maximum growth rate for ammonium oxidizers was found to be 1.22 day(-1). Modeling studies also validated the recovery period as 10 days.

Effect of acetate to biomass ratio on simultaneous polyhydroxybutyrate generation and direct microbial growth in fast growing microbial culture.

The study investigated the effect of variations in the acetate to biomass ratio on substrate storage potential, and the kinetics of substrate utilization. A series of batch experiments were conducted with biomass taken from the fill and draw reactor operated at a sludge age of 2 d. One of the batch reactors duplicated the substrate loading in the main reactor. The others were started with different initial acetate to biomass ratios both in lower and higher ranges. Increasing available acetate did not totally divert excess substrate to storage; the microbial culture adjusted the kinetics of the metabolic reactions to a higher growth rate so that more substrate could be utilized for direct growth at high acetate levels. Conversely, storage rate was increased, utilizing a higher substrate fraction for polyhydroxybutyrate generation when acetate concentration was lowered. The physiological and molecular bases of storage at low substrate levels were discussed.

Potential of ultrafiltration for organic matter removal in the polymer industry effluent based on particle size distribution analysis.

The purpose of the study was the experimental evaluation of ultrafiltration as a potential innovative technology for the removal of organic matter of around 15,000 mg chemical oxygen demand (COD) per liter in the polymer industry wastewater. Particle size distribution (PSD) analysis served as the major experimental instrument along with conventional chemical settling. Biodegradation characteristics of the remaining COD after ultrafiltration were determined by model interpretation of the corresponding oxygen uptake rate (OUR) profile. The study first involved a detailed characterization of the polymer wastewater including PSD analysis of the COD content. Chemical treatability was investigated using lime alone and with ferric chloride as coagulants followed with a PSD assessment of the chemically settled effluent. Modeling of the OUR profile generated by the ultrafiltration effluent defined related biodegradation kinetics and provided information on the overall COD removal potential. PSD analysis indicated that more than 70 % of the total COD accumulated in the 220- to 450-nm size range. It indicated that ultrafiltration was potentially capable of removing more than 90 % of the COD with an effluent lower than 1,500 mg COD/L. Chemical settling with 750 mg/L of FeCl(3) dosing at a pH of 7.0 provided a similar performance. The ultrafiltration effluent included mainly hydrolysable COD and proved to be biodegradable, with the process kinetics compatible with domestic sewage. PSD evaluation proved to be a valuable scientific instrument for underlining the merit of ultrafiltration as the appropriate innovative technology for polymer wastewater, removing the major portion of the COD in a way that is suitable for recovery and reuse and producing a totally biodegradable effluent.

Identification of nitrifiers in a full-scale biological treatment system using fluorescent in situ hybridization.

Diversity of nitrifying bacterial population was investigated in sludge samples taken from a full-scale biological wastewater treatment plant (WWTP) treating domestic wastewater by fluorescent in situ hybridization (FISH) during seasonal operation. Duplicate grab samples were collected in March 2003, June 2003, December 2003 and May 2004 from the aerobic tank of the treatment plant. FISH results were interpreted with system performance in terms of BOD5, TKN and NO3-N removals and also with operational parameters such as wastewater temperature and sludge age. BOD5 removal efficiencies were always greater than 90% whilst TKN removal in a range of 69-95% were achieved during the monitoring period. Although there were variations in operational conditions of the biological treatment system both Nitrosomonas and Nitrosospira genera from AOB and Nitrobacter genus from NOB were found to be present in all samples examined.

Effluent management for a metal finishing industry aiming zero discharge conditions.

Technical applicability of zero discharge conditions is evaluated for the specific case of a large metal finishing industry located within the protection zone of a surface water body designated as a potential source for domestic water supply. Within the context of a sound water management strategy, a detailed process profile of the plant is established with relevant balance between water demand and wastewater generation. Quality restrictions for various water uses are identified. Wastewater flows are segregated depending on significant quality parameters. A comprehensive treatment scheme is defined for optimum wastewater recycle and reuse. Source allocation is made for the reuse of different streams of recycled wastewater. The study indicates that wastewater reuse can only be implemented with an efficiency of around 85-90% for the selected industry.

Optimization of nitrogen removal for alternating intermittent aeration-type activated sludge system: a new process modification.

A new activated sludge process modification was proposed for intermittent aeration process to achieve more stable nitrogen removal performance. A single completely mixed reactor was divided into two compartments in series and operated in intermittent aeration mode by using activated sludge simulation model. The new configuration provided competetive advantage on nitrification as well as denitrification capacity, compared to the intermittently aerated system with a single reactor. In addition, the dissolved oxygen set-point control during air-on periods was found to be an important parameter in terms of nitrogen removal.

Propionate oxidation by and methanol inhibition of anaerobic ammonium-oxidizing bacteria.

Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway and a cost-effective way to remove ammonium from wastewater. Anammox bacteria have been described as obligate chemolithoautotrophs. However, many chemolithoautotrophs (i.e., nitrifiers) can use organic compounds as a supplementary carbon source. In this study, the effect of organic compounds on anammox bacteria was investigated. It was shown that alcohols inhibited anammox bacteria, while organic acids were converted by them. Methanol was the most potent inhibitor, leading to complete and irreversible loss of activity at concentrations as low as 0.5 mM. Of the organic acids acetate and propionate, propionate was consumed at a higher rate (0.8 nmol min(-1) mg of protein(-1)) by Percoll-purified anammox cells. Glucose, formate, and alanine had no effect on the anammox process. It was shown that propionate was oxidized mainly to CO(2), with nitrate and/or nitrite as the electron acceptor. The anammox bacteria carried out propionate oxidation simultaneously with anaerobic ammonium oxidation. In an anammox enrichment culture fed with propionate for 150 days, the relative amounts of anammox cells and denitrifiers did not change significantly over time, indicating that anammox bacteria could compete successfully with heterotrophic denitrifiers for propionate. In conclusion, this study shows that anammox bacteria have a more versatile metabolism than previously assumed.

European union water policy--tasks for implementing "Water Framework Directive" in pre-accession countries.

Water Framework Directive aiming to maintain and improve the aquatic environment in the EU was launched by the European Parliament in 2000. According to this directive, control of quantity is an ancillary element in securing good water quality and therefore measures on quantity, serving the objective of ensuring good quality should also be established. Accordingly, it is a comprehensive and coordinated package that will ensure all European waters to be protected according to a common standard. Therefore, it refers to all other Directives related to water resources management such as Urban Wastewater Treatment Directive Nitrates Directive, Drinking Water Directive, Integrated Pollution Prevention Control etc. Turkey, as a candidate state targeting full-membership, should comply the necessary preparations for the implementation of the "Water Framework Directive" as soon as possible. In this study, the necessary legislative, political, institutional, and technical attempts of the pre-accession countries have been discussed and effective recommendations have been offered for future activities in Turkey.

Wastewater reuse for the minimization of fresh water demand in coastal areas--selected cases from the textile finishing industry.

Availability of water to the industry often becomes prohibitive, both in terms of quality and cost, in coastal areas. This study takes the textile industry and evaluates the prerequisites of water recovery and reuse. In this context, a large spectrum are studied for their water, the general quality of wastewater generated, quality and treatability of reuse wastewater streams, and expected changes in the overall effluent quality after segregation of the recovery wastewater portion.

Implementation of the Anammox process for improved nitrogen removal.

Stringent standards for nitrogen discharge necessitate the implementation of new systems for the sustainable removal of ammonium from wastewater. One of such systems is based on the process of anaerobic ammonium oxidation (Anammox), which is a new powerful tool especially for strong nitrogenous wastewaters. In this study, the Anammox process performance was tested with synthetic wastewater in a completely stirred tank reactor (CSTR). The reactor was operated for 511 days and fed with increasing amounts of ammonium and nitrite. In this period, an increase of ammonium and nitrite utilization rates were observed as a result of the increase of nitrogen loads in the influent. After 272 days, about 60% of the biomass was removed from the reactor and the system was restarted. Throughout 511 days 90% of the ammonium and more than 99% of the nitrite were converted mainly to dinitrogen (N2) and nitrate. The microbial community in the reactor was characterized with Fluorescence in situ Hybridization (FISH). The study showed that the population in the reactor was dominated by the deep-branching planctomycete Candidatus "Brocadia anammoxidans" strain Dokhaven 2.