Biological Wastewater Treatment

The objective of the study was to evaluate the phytoremediation potential of three aquatic macrophytes (Commelina cyanea, Phragmites australis and Water Hyacinth (Eichhornia crassipes)) for treatment of municipal wastewater collected from Federal University of Technology, Akure (Nigeria). Laboratory scale of three constructed wetlands of dimensions 0.43 m x 0.93 m x 0.36 m in width, length and depth respectively, were developed to mimic natural conditions and was operated for a single experimental run with each macrophte at different retention time of 6, 9 and 12 days. These aquatic macrophytes were planted in separate ponds. Domestic wastewater from undergraduate students' hostel was introduced to the ponds. The raw wastewater sample and treated wastewater samples were analysed using standard laboratory methods for physical (Turbidity and Dissolved solids), chemical (pH, Nitrate, Nitrite, Phosphate, Sulphate Chemical Oxygen Demand and Biochemical Oxygen Demand) and bacteriological (Coliform bacteria) parameters. Results showed substantial diminutions in all parameters treated with the phytoremediators during the course of the study. Asides the three plants effectively removing Nitrate, Nitrite, phosphate and Sulphate pollutants, Phragmites australis gave the highest removal efciency for Phosphate (85.8%), Water hyacinth gave the highest removal efciency for pH (11.5%), Biochemical Oxygen Demand and Coliform bacteria and Commelina cyanea gave the highest removal efciency for turbidity (96.9%) and dissolved solids (82.9%) parameters of the domestic wastewater samples. The overall results of the phytoremediation studies indicate that the purication effectiveness of the three aquatic macrophytes were spontaneous, feasible and remarkable.

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract This study aims to examine the economic and environmental benefits of recovered paper and potential contribution of the recovered paper to the Kingdom of Saudi Arabia (KSA) Vision 2030. The Vision 2030 is an inclusive development policy, recently launched, with the objectives to build the best future for the country. The Vision 2030 is based on three ambitious goals: making the country a vibrant society, a thriving economy and an ambitious nation. It is estimated that by 2030, 5.05 million ton of waste paper would be recovered in the country. About 11.3 billion SAR (US $3.01 billion) would be added to the country's GDP and would create about 16,536 new jobs if the recovered paper industry is built in the country. Moreover, a net environmental benefit of 9.6 million crude barrel oil savings and 4.5 million ton of CO2 savings from GHG emissions could be achieved by 2030 only from the paper waste recovery in the country. The potential benefits of paper waste recycling in KSA highlight the needs of effective measures to optimize the economic and environmental opportunities inherited in the waste paper industry. These measures should focus on capitalizing the local waste paper processing industry, restrict the export of raw waste paper materials, and enhance the waste paper collection process and quantity.

Industries play a major role in the economic growth of developing countries.
However, these are also the major source of environmental pollution because
all types of industries discharge a huge volume of wastewater into the
environment, which causes serious soil and water pollution as well as serious
health threats in living beings. There are many types of industrial
wastewaters based on different industries such as distilleries, tanneries,
textile, pulp and paper industries, pharmaceuticals, electroplating, iron and
steel, mine and quarries, etc. Each industry produces its own particular
combination of organic and inorganic pollutants such as melanoidins,
lignin, dyes, pesticides, pigments, phenols, chlorophenol, toxic heavy metals
and a many recalcitrant pollutants. Industrial wastewaters contains a
variety of organic and inorganic pollutants and if discharged into the
environment without adequate treatment, causes serious environmental
problems and health hazards in all living organisms. Therefore, proper
treatment of industrial wastewaters is essential for environmental safety.
Thus, this chapter provides the detail knowledge on the nature and
characteristics of different industrial wastewaters, major organic and
inorganic pollutants present in different industrial wastewaters, their
toxicological effects in environment and health hazards as well as various
treatment approaches using microbes for the sustainable environment. In
addition, the advances, merits, and demerits of various microbial treatment
methods used for the treatment of industrial wastewaters are also discussed.

This Guide identifies several unconventional methods to treat sewage at different population scales. It describes the technical characteristics, makes cost per capita analysis and proposes policy recommendations in unconventional sewage treatment.

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract In the Kingdom of Saudi Arabia (KSA), millions of worshippers come from across the globe to perform religious rituals of Pilgrimage (Hajj) and Umrah. Madinah-tul-Munawara is one of the holiest city, where pilgrims come after performing rituals in Makkah. In this city, most of the collected municipal solid waste (MSW) is disposed of in the landfills after a partial recycling of paper, cardboard, and metals (~10-20% of total MSW). The Saudi's government has recently launched a new policy of Vision 2030, which outlined the safeguard of local environment through increased efficiency of waste recycling and management, pollution prevention strategies and generating renewable energy from indigenous sources, including the waste. Currently, the recycling practices in KSA are mainly regulated by an informal sector through waste pickers or waste scavengers. This has led to the need of recycling schemes, especially in the holiest cities of Makkah and Madinah through a public-private partnership (PPP). Huge amounts of energy can be conserved, that would otherwise be spent on raw material extraction, transportation, and manufacturing of materials, through recycling into the same materials. Around 10,009 TJ of energy can be saved through recycling of 24.21% of MSW in Madinah city, including glass, metals, aluminum, cardboard, and paper. It is estimated that around 10,200 tons of methane (CH4) emissions and 254,600 Mt.CO2 eq. of global warming potential (GWP) can also be saved. In addition, carbon credit revenue of US $5.92 million, and landfill diversion worth of US $32.78 million can be achieved with a net revenue of US $49.01 million every year only by recycling 24.21% of MSW in Madinah city. The waste recycling doesn't require high technical skills and labor, and complicated technologies for large-scale implementation, and therefore, can be implemented easily in the holiest cities of Makkah and Madinah to achieve multiple economic and environmental benefits. Abstract In the Kingdom of Saudi Arabia (KSA), millions of worshippers come from across the globe to perform religious rituals of Pilgrimage (Hajj) and Umrah. Madinah-tul-Munawara is one of the holiest city, where pilgrims come after performing rituals in Makkah. In this city, most of the collected municipal solid waste (MSW) is disposed of in the landfills after a partial recycling of paper, cardboard, and metals (~10-20% of total MSW). The Saudi's government has recently launched a new policy of Vision 2030, which outlined the safeguard of local environment through increased efficiency of waste recycling and management, pollution prevention strategies and generating renewable energy from indigenous sources, including the waste. Currently, the recycling practices in KSA are mainly regulated by an informal sector through waste pickers or waste scavengers. This has led to the need of recycling schemes, especially in the holiest cities of Makkah and Madinah through a public-private partnership (PPP). Huge amounts of energy can be conserved, that would otherwise be spent on raw material extraction, transportation, and manufacturing of materials, through recycling into the same materials. Around 10,009 TJ of energy can be saved through recycling of 24.21% of MSW in Madinah city, including glass, metals, aluminum, cardboard, and paper. It is estimated that around 10,200 tons of methane (CH4) emissions and 254,600 Mt.CO2 eq. of global warming potential (GWP) can also be saved. In addition, carbon credit revenue of US $5.92 million, and landfill diversion worth of US $32.78 million can be achieved with a net revenue of US $49.01 million every year only by recycling 24.21% of MSW in Madinah city. The waste recycling doesn't require high technical skills and labor, and complicated technologies for large-scale implementation, and therefore, can be implemented easily in the holiest cities of Makkah and Madinah to achieve multiple economic and environmental benefits.

Excess sludge treatment and disposal currently represents a rising challenge for wastewater treatment plants (WWTPs) due to economic, environmental and regulation factors. There is therefore considerable impetus to explore and develop strategies and technologies for reducing excess sludge production in biological wastewater treatment processes. This paper reviews current strategies for reducing sludge production based on these mechanisms: lysis-cryptic growth, uncoupling metabolism, maintenance metabolism, and predation on bacteria. The strategies for sludge reduction should be evaluated and chosen for practical application using costs analysis and assessment of environmental impact. High costs still limit technologies of sludge ozonation-cryptic growth and membrane bioreactor from spreading application in full-scale WWTPs. Bioacclimation and harmful to environment are major bottlenecks for chemical uncoupler in practical application. Sludge reduction induced by oligochaetes may present a cost-effective way for WWTPs if unstable worm growth is solved. Employing any strategy for reducing sludge production may have an impact on microbial community in biological wastewater treatment processes. This impact may influence the sludge characteristics and the quality of effluent. r

— Due to the reduction of groundwater resources, the artificial recharge of these resources through the reuse of treated wastewater (modified water) is an efficient way to tackle the problem. Some of the most important goals to be achieved regarding such a situation are the development of underground resources, building barriers to help avoid the penetration of the saline water to the underground water table in the coastal areas, creating additional levels of water treatment by soil and controlling the soil settlement. The modified water helps to compensate for the underground water. Asthe additional stage of the purification of the modified water offers assurance on the sewage management system, this natural water treatment created underground eliminates the need for costly wastewater treatment processes. Moreover, the groundwater aquifers provide a natural mechanism for the subsurface transfer of the modified water and eliminate the need for the surface storage facilities and associated problems, such as evaporatio n and the growth of algae, which degrade the water quality. One of the most commonly used methods is the aquifer storage and recovery (ASR) technology, which helps overcome the seasonal imbalance associated with the retrieval systems in the world. In the present paper, the methods used to realize this solution, including among others flood spreading, the soil aquifer treatment (SAT) systems, injection in unsaturated areas, and direct injection are examined. Furthermore, the advantages and disadvantages of using the modified water and the required hydraulic analyzes for designing direct injection wells and injection in unsaturated areas will also be investigated.

In aerobic bioprocesses, oxygen is a key substrate; due to its low solubility in broths (aqueous solutions), a continuous supply is needed. The oxygen transfer rate (OTR) must be known, and if possible predicted to achieve an optimum design operation and scale-up of bioreactors. Many studies have been conducted to enhance the efficiency of oxygen transfer. The dissolved oxygen concentration in a suspension of aerobic microorganisms depends on the rate of oxygen transfer from the gas phase to the liquid, on the rate at which oxygen is transported into the cells (where it is consumed), and on the oxygen uptake rate (OUR) by the microorganism for growth, maintenance and production. The gas-liquid mass transfer in a bioprocess is strongly influenced by the hydrodynamic conditions in the bioreactors. These conditions are known to be a function of energy dissipation that depends on the operational conditions, the physicochemical properties of the culture, the geometrical parameters of the bioreactor and also on the presence of oxygen consuming cells. Stirred tank and bubble column (of various types) bioreactors are widely used in a large variety of bioprocesses (such as aerobic fermentation and biological wastewater treatments, among others). Stirred tanks bioreactors provide high values of mass and heat transfer rates and excellent mixing. In these systems, a high number of variables affect the mass transfer and mixing, but the most important among them are stirrer speed, type and number of stirrers and gas flow rate used. In bubble columns and airlifts, the lowshear environment compared to the stirred tanks has enabled successful cultivation of shear sensitive and filamentous cells. Oxygen transfer is often the rate-limiting step in the aerobic bioprocess due to the low solubility of oxygen in the medium. The correct measurement and/or prediction of the volumetric mass transfer coefficient, (k L a), is a crucial step in the design, operation and scale-up of bioreactors. The present work is aimed at the reviewing of the oxygen transfer rate (OTR) in bioprocesses to provide a better knowledge about the selection, design, scale-up and development of bioreactors. First, the most used measuring methods are revised; then the main empirical equations, including those using dimensionless numbers, are considered. The possible increasing on OTR due to the oxygen consumption by the cells is taken into account through the use of the biological enhancement factor. Theoretical predictions of both the volumetric mass transfer coefficient and the enhancement factor that have been recently proposed are described; finally, different criteria for bioreactor scale-up are considered in the light of the influence of OTR and OUR affecting the dissolved oxygen concentration in real bioprocess.

A strategy for adaptive control and energetic optimization of aerobic fermentors was implemented, with both air flow and agitation speed as manipulated variables. This strategy is separable in its components: control, optimization, estimation. We optimized parameter’s estimation (from the usual KLa correlation) using sinusoidal excitation of air flow and agitation speed. We have implemented parameter’s estimation trough recursive least squares algorithm with forgetting factor. We carried separate essays on control, optimization and estimation algorithms. We carried our essays using an original computational simulation environment, with noise and delay generating facilities for data sampling and filtering.

Our results show the convergence and robustness of the estimation algorithm used, improved with use of both forgetting factor and KLa dead-band facilities. Control algorithm used in our work compares favorably with PID using the integrated area criteria for deviation between oxygen molarity and critical molarity (set point). Optimization algorithm clearly reduces energetic consumption, respecting critical molarity. Integration of control, optimization and adaptive algorithms was implemented, but future work is needed for stability. Methods were defined and implemented for stability improvement. We have implemented data acquisition and computer manipulation of air flow and agitation speed for actual fermentors.

Membrane bioreactor (MBR) is a reliable and promising technology for wastewater treatment and reclamation applications. In spite of more than a decade of significant advances in developing fouling mitigation methods, different physical and cleaning protocols are still necessary to be developed to limit the membrane fouling. The use of scouring agents in MBR applications has been paid attention as a new approach as an energy-efficient way to control membrane fouling. Recently, mechanical cleaning by scouring agents is becoming as intense research area considering high efficiency of fouling reduction while requiring low energy consumption. In this review, fundamental and comprehensive assessments of the mechanical cleaning concepts and their applications with porous and nonporous scouring agents for MBR system are critically reviewed. The existing challenges and future research prospects on the mechanical cleaning technology associated with scouring agents for the MBR applications are also discussed.

Cheese whey is a type of dairy wastewater that is either discharged directly into the environment or the local sewer, treated with the primary object to meet effluent discharge limits, or used as a resource to produce, for example, biofuels, single cell proteins, animal feed after condensation, sweetener after crystallization of lactose, xanthan gum, glycerol and 2,3 butanediol upon fermentation. This review has been dedicated to the production of biofuels, specifically biogas, from cheese whey. We aim to provide the reader with a brief account of how knowledge in the field of biogas production from cheese whey effluents has evolved, the current status quo, and identify areas that should be addressed in the near future. Based on the review of ca. 100 research papers published over the past 25 years following facts were extracted: A large body of knowledge exists at lab- and pilot-scale. It has been shown that cheese whey wastewater can be used either as a primary or co-substrate for the production of biomethane and biohydrogen. Amongst the reactors studied, high-rate anaerobic digesters can be operated at organic loading rates up to 40 g COD L-1 d-1 with relatively low hydraulic retention times (0.5-10 d). The 1980ies have seen the implementation of the first fully integrated systems in New Zealand and Ireland. It was also concluded that anaerobic treatment of full-strength cheese whey, despite COD removal efficiencies of up to 99%, cannot meet the stringent discharge criteria set forth in most countries thus requiring an aerobic polishing step. As the biogas technology reaches technical maturity and enters the commercial stage in the dairy industry, more data and reliable statistics are needed to evaluate the economical and operational feasibility at the industrial scale, including how we deal with the anaerobic digester effluent. Life cycle and carbon footprint assessments of the overall treatment process are to be carried out before it can be promoted as a technology that can contribute towards sustainable development and a more environmentally friendly agro-industry. Cooperation and promotion should be encouraged among agro-industries, government and national research institutes as well as providers of technology, operators and clients of digestion products. Consequently, decision makers will be able to choose the best technologies and options to promote the digestion products. It should also be recognized that the competition between different processes exploiting cheese whey as a resource will continue due to technological advances.

Reclaimed water from small wastewater treatment facilities in the rural areas of the Beira Interior region (Portugal) may constitute an alternative water source for aquifer recharge. A 21-month monitoring period in a constructed wetland treatment system has shown that 21,500 m 3 year −1 of treated wastewater (reclaimed water) could be used for aquifer recharge. A GIS-based multi-criteria analysis was performed, combining ten thematic maps and economic, environmental and technical criteria, in order to produce a suitability map for the location of sites for reclaimed water infiltration. The areas chosen for aquifer recharge with infiltration basins are mainly composed of anthrosol with more than 1 m deep and fine sand texture, which allows an average infiltration velocity of up to 1 m d −1 . These characteristics will provide a final polishing treatment of the reclaimed water after infiltration (soil aquifer treatment (SAT)), suitable for the removal of the residual load (trace organics, nutrients, heavy metals and pathogens). The risk of groundwater contamination is low since the water table in the anthrosol areas ranges from 10 m to 50 m. On the other hand, these depths allow a guaranteed unsaturated area suitable for SAT. An area of 13,944 ha was selected for study, but only 1607 ha are suitable for reclaimed water infiltration. Approximately 1280 m 2 were considered enough to set up 4 infiltration basins to work in flooding and drying cycles.

The expanded granular sludge bed bioreactor appears today as a cheap, robust and more popular technology because it operates using a fluidized bed, which allows increasing in organic load and in cell retention times, generating higher treatment efficiencies (up to 95 %) and renewable energy (i.e., biogas, biomethane, and biohydrogen). Nevertheless, the efficiency of this bioreactor mainly depends on the operating conditions. Thus, the content presented in this review paper focuses on the analysis of the operating conditions and performance of expanded granular sludge bed bioreactor for treating different types of industrial, agro-industrial and domestic wastewaters (e.g., agro-food, beverage, alcohol distillery, tannery, slaughterhouse, chemical, pharmaceutical, municipal sewage, among others). Because of this reason, this study aimed to analyze the operating conditions and type of substrate, which has been used in these bioreactors to improve future research to wastewater treatment and renewable energy production. According to the review, it is concluded that the EGSB bioreactor is a novel sustainable alternative to treat different types of wastewaters and consequently change the paradigm of wastewater management from "treatment and disposal" to "beneficial use" as well as "profitable effort".

This review analyzes the state-of-the-art of a specific niche in biological wastewater treatment that uses immobilized eukaryotic microalgae (and several prokaryotic photosynthetic cyanobacteria), with emphasis on removing nutrients with the support of microalgae growth-promoting bacteria. Removal of other pollutants by this technology, such as heavy metals and industrial pollutants, and technical aspects related to this specific subfield of wastewater treatment are also presented. We present a general perspective of the field with most known examples from common literature, emphasizing a practical point of view in this technologically oriented topic. The potential venues of future research in this field are outlined and a critical assessment of the failures, limitations, and future of immobilized microalgae for removal of pollutants is presented.

The disposal of wastewater is a problem of great concern throughout the world specifically in developing countries. This study investigates the impact of indiscriminate wastewater disposal on soil in Akindeko and Abiola halls of residence at the Federal University of Technology, Akure Nigeria. Soil samples were taken from the wastewater disposal site at the surface and varying depths of 10 cm and 20 cm while the control samples were taken 10 m away from the polluted soil surface. Physico-chemical and bacteriological properties determined include; colour, odour, soil weight, particle weight, bulk density, porosity, pH, Copper, Manganese, Zinc, Lead, Cadmium, Cobalt, Iron, Sodium, Potassium, Calcium, Magnesium, bacteria, fungi and coliforms. The results showed that all the physicochemical and bacteriological properties of the soils have relatively high concentration indicating pollution compared to the control samples. The pH ranged from 8.7 to 7.2 while Ca and K have a range of 1277 ppm to 773 ppm and 1273 ppm to 754 ppm respectively. The highest concentration of Zn and Mn are 19.30 ppm and 11.70 ppm respectively. It is recommended that a sustainable wastewater treatment plant should be provided to treat all wastewater generated from all hall of residence in the university and at the same time the soils in the area require various remediation technologies like bioremediation and phytoremediation by growing certain plants in the area to minimize the rate of contamination and extent of future pollution problems. This will go a long way in preventing environmental pollution in the study area.

Lacking adequate supervision on quality of state wastewater treatment plants causes these materials to enter the environment raw and in most cases with no consolidation and cause lots of losses to the natural environment. Samples: Samples were prepared in plastic cylinders with nearly 14 cm diameter and 50 cm height. Silica sand was poured into cylinders in three layers, bottom to up and tiny to coarse. Aligoudarz wastewater treatment plant was used for irrigation of lysimeters. On one hand, the operation of four-seed powder together with silica sand was remarkable in decreasing the number of coliforms. And removal efficiency for total coliforms and fecal coliforms were 98% and 99%, respectively. Using this method in refining urban wastewater can increase wastewater microbial quality to the high degree and can be used in agricultural land, feeding underground water resources, entering surface water, green space irrigation and using in car washes and etc.

The aim of this research was to study the accumulation and removal of heavy metals (Cd, Cu, Pb, Zn) by a biological wastewater treatment system. Heavy metal contents in the influent and effluent wastewater were compared. Also, the heavy metal contents in the sludge before and after anaerobic digestion were compared. The results showed: (1) more pronounced variations in the contents of Cu and Zn than that of Cd and Pb, which showed that at 0.02 for Cd and 0.05 mg/l for Pb, the reduction in their contents was insignificant; (2) that removal of heavy metals was directly proportional to their initial contents in the influent wastewater. Corresponding to the influent contents, in increasing order, the reduction in heavy metal contents was: Cd< Pb <Cu < Zn; and (3) that anaerobic stabilization of sludge caused an increase in heavy metal contents on dry weight basis. The order of increase in heavy metal contents in digested sludge (Zn< Pb< Cu < Cd) was opposite to that of their contents removal from influent wastewater. #

Mounding often occurs beneath engineering structures designed to infiltrate reuse water. AQTESOLV software and a spreadsheet solution for Hantush, together with soil moisture water balance (SWAGMAN farm model), were used for quantitatively predicting the height and extent of groundwater mounding underground to assess the groundwater-flow simulations of infiltration from a hypothetical irrigation site. Horizontal and vertical permeability, aquifer thickness, specific yield, and basin geometry are among the aquifer and recharge properties inputs. For 2.2 ha sites, the maximum heights of the simulated groundwater mound ranges up to 0.29 m. The maximum areal extent of groundwater mounding measured from the edge of the infiltration basins of 0.24 m ranges from 0 to 75 m. Additionally, the simulated height and extent of the groundwater mounding associated with a hypothetical irrigation infiltration basin for 2.2 ha development may be applicable to sites of different sizes, using the recharge rate estimated from the SWAGMAN farm model. For example, for a 2.2 ha site with a 0.0002 m/day recharge rate, the irrigation infiltration basin design capacity (and associated groundwater mound) would be the same as for a 1.1 ha site with a 0.0004 m/day recharge rate if the physical characteristics of the aquifer are unchanged. The study claimed that the present modelling approach overcomes the complications of solving the Hantush equation for transient flow. The approach utilised in this study can be applied for other purposes such as measuring the feasibility of infiltrating water, attenuation zone, risk mitigation essential for decision-makers and planning regulators in terms of environmental effects and water use efficiency.

Today, due to the growing population on the one hand and the shortage of drinking water resources on the other the use of water recycling has grown dramatically. The use of artificial wetlands is one of the wastewater treatment methods its output can be used without problems in the environment or in agriculture. An important issue in these systems the exact knowledge and correct recognition of the type of plant species used in the system. In this study the removal efficiency of nutrients by sedge plant has been investigated in order to determine the possibility of using this plant in artificial wetland system. For this purpose, four cells were considered. The conditions were completely identical in all cells one cell was also considered to have a course of growth with normal water (control cell). After 6 months the plant was sampled and the individual organs and underground samples were tested and the removal efficiency of nutrients was determined. The percentage of nutrient removal by the plant and by the total cell system for sedge was %58.6 N, %35.71 P, %73.64 N, %56.25P, respectively.

Most of the wastewater treatment systems in small rural communities of the Cova da Beira region (Portugal) consist of constructed wetlands (CW) with horizontal subsurface flow (HSSF). It is believed that those systems allow the compliance of discharge standards as well as the production of final effluents with suitability for reuse. Results obtained in a nine-month campaign in an HSSF bed pointed out that COD and TSS removal were lower than expected. A discrete sampling also showed that removal of TC, FC and HE was not enough to fulfill international irrigation goals. However, the bed had a very good response to variation of incoming nitrogen loads presenting high removal of nitrogen forms. A good correlation between mass load and mass removal rate was observed for BOD5, COD, TN, NH4-N, TP and TSS, which shows a satisfactory response of the bed to the variable incoming loads. The entrance of excessive loads of organic matter and solids contributed for the decrease of the effective volume for pollutant uptake and therefore, may have negatively influenced the treatment capability. Primary treatment should be improved in order to decrease the variation of incoming organic and solid loads and to improve the removal of COD, solids and pathogenic. The final effluent presented good physical–chemical quality to be reused for irrigation, which is the most likely application in the area.

In aerobic bioprocesses, oxygen is a key substrate; due to its low solubility in broths (aqueous solutions), a continuous supply is needed. The oxygen transfer rate (OTR) must be known, and if possible predicted to achieve an optimum design operation and scale-up of bioreactors. Many studies have been conducted to enhance the efficiency of oxygen transfer. The dissolved oxygen concentration in a suspension of aerobic microorganisms depends on the rate of oxygen transfer from the gas phase to the liquid, on the rate at which oxygen is transported into the cells (where it is consumed), and on the oxygen uptake rate (OUR) by the microorganism for growth, maintenance and production. The gas-liquid mass transfer in a bioprocess is strongly influenced by the hydrodynamic conditions in the bioreactors. These conditions are known to be a function of energy dissipation that depends on the operational conditions, the physicochemical properties of the culture, the geometrical parameters of the bioreactor and also on the presence of oxygen consuming cells. Stirred tank and bubble column (of various types) bioreactors are widely used in a large variety of bioprocesses (such as aerobic fermentation and biological wastewater treatments, among others). Stirred tanks bioreactors provide high values of mass and heat transfer rates and excellent mixing. In these systems, a high number of variables affect the mass transfer and mixing, but the most important among them are stirrer speed, type and number of stirrers and gas flow rate used. In bubble columns and airlifts, the lowshear environment compared to the stirred tanks has enabled successful cultivation of shear sensitive and filamentous cells. Oxygen transfer is often the rate-limiting step in the aerobic bioprocess due to the low solubility of oxygen in the medium. The correct measurement and/or prediction of the volumetric mass transfer coefficient, (k L a), is a crucial step in the design, operation and scale-up of bioreactors. The present work is aimed at the reviewing of the oxygen transfer rate (OTR) in bioprocesses to provide a better knowledge about the selection, design, scale-up and development of bioreactors. First, the most used measuring methods are revised; then the main empirical equations, including those using dimensionless numbers, are considered. The possible increasing on OTR due to the oxygen consumption by the cells is taken into account through the use of the biological enhancement factor. Theoretical predictions of both the volumetric mass transfer coefficient and the enhancement factor that have been recently proposed are described; finally, different criteria for bioreactor scale-up are considered in the light of the influence of OTR and OUR affecting the dissolved oxygen concentration in real bioprocess.

This paper presents an example of the importance of evapotranspiration in constructed wetlands, with vertical subsurface flow, comparing different methods of treatment efficiency calculations and discussing the influence of evapotranspiration on removal rates. The application of reed, marked by high transpiration ability, is a cheap and effective method of landfill leachate disposal. A 2-year study examined the effectiveness of leachate treatment in constructed wetlands with reed. Two kinds of vertical subsurface flow systems: first with sand, and second with combined two layers of sewage sludge and sand has been tested. 1, 3, and 5 mm d−1 hydraulic loading rates of landfill leachate have been applied. Daily evapotranspiration was in the range from 0.98 to 2.99 mm d−1 in the first year of research and from 2.56 to 4.61 mm d−1 in the second year. The influence of evapotranspiration rate on chemical oxygen demand (COD) removal rate was examined. Two methods of removal efficiency calculation have been used: first based on inlet and outlet COD concentrations, second on mass balance determination. Research showed that the removal efficiency calculated as a comparison between initial and final concentration is significantly lower, than expected from mass balance, especially, when higher hydraulic loading rates were applied.

In Canada, increases in rural development has led to a growing need to effectively manage the resulting municipal and city sewage without the addition of significant cost- and energy- expending infrastructure. Storring Septic Service Limited is a family-owned, licensed wastewater treatment facility located in eastern Ontario. It makes use of a passive waste stabilization pond system to treat and dispose of waste and wastewater in an environmentally responsible manner. Storring Septic, like many other similar small-scale wastewater treatment facilities across Canada, has the potential to act as a sustainable eco-engineered facility that municipalities and service providers could utilize to manage and dispose of their wastewater. However, it is of concern that the substantial inclusion of third party material could be detrimental to the stability and robustness of the pond system. In order to augment the capacity of the current facility, and ensure it remains a self-sustaining system with the capacity to safely accept septage from other sewage haulers, it was hypothesized that pond effluent treatment could be further enhanced through the incorporation of one of three different technology solutions, which would allow the reduction of wastewater quality parameters below existing regulatory effluent discharge limits put in place by Ontario’s Ministry of the Environment and Climate Change (MOECC). Two of these solutions make use of biofilm technologies in order to enhance the removal of wastewater parameters of interest, and the third utilizes the natural water filtration capabilities of zebra mussels. Pilot-scale testing investigated the effects of each of these technologies on treatment performance under both cold and warm weather operation. This research aimed to understand the important mechanisms behind biological filtration methods in order to choose and optimize the best treatment strategy for full-scale testing and implementation. In doing so, a recommendation matrix was developed with the potential to be used as a universal operational strategy for wastewater treatment facilities located in environments of similar climate and ecology.

Reclaimed water from small wastewater treatment facilities in the rural areas of the Beira Interior region (Portugal) may constitute an alternative water source for aquifer recharge. A 21-month monitoring period in a constructed wetland treatment system has shown that 21,500 m3 year−1 of treated wastewater
(reclaimed water) could be used for aquifer recharge. A GIS-based multi-criteria analysis was performed, combining ten thematic maps and economic, environmental and technical criteria, in order to produce a suitability map for the location of sites for reclaimed water infiltration. The areas chosen for aquifer
recharge with infiltration basins are mainly composed of anthrosol with more than 1 m deep and fine sand texture, which allows an average infiltration velocity of up to 1 m d−1. These characteristics will provide a final polishing treatment of the reclaimed water after infiltration (soil aquifer treatment (SAT)),
suitable for the removal of the residual load (trace organics, nutrients, heavy metals and pathogens).
The risk of groundwater contamination is low since the water table in the anthrosol areas ranges from 10 m to 50 m. On the other hand, these depths allow a guaranteed unsaturated area suitable for SAT. An area of 13,944 ha was selected for study, but only 1607 ha are suitable for reclaimed water infiltration.
Approximately 1280 m2 were considered enough to set up 4 infiltration basins to work in flooding and
drying cycles.

El modelo de CARTA DE INTENCIÓN, se basa en la experiencia conjunta del organismo de investigación y educación superior pública denominado Centro de Investigación en Energía de la Universidad Nacional Autónoma de México CIE,  y la empresa tecnológica denominada Visión EnerGtiK Sociedad Microindustrial . 
La intención, puesta por escrito en este modelo de carta, es la de  firmar y operar un acuerdo de colaboración entre ellas  con la finalidad de establecer las bases generales de apoyo y colaboración, para que ambas partes, en ejercicio de sus atribuciones, lleven a cabo tareas inherentes a los campos de trabajo de los estudiantes del “CENTRO”  como medio para complementarlos y enriquecerlos.

Moving bed biofilm reactor (MBBR) Hydrolysis Predation Pulp and viscose wastewater a b s t r a c t An integrated mathematical model is proposed for modelling a moving bed biofilm reactor (MBBR) for removal of chemical oxygen demand (COD) under aerobic conditions. The composite model combines the following: (i) a one-dimensional biofilm model, (ii) a bulk liquid model, and (iii) biological processes in the bulk liquid and biofilm considering the interactions among autotrophic, heterotrophic and predator microorganisms. Depending on the values for the soluble biodegradable COD loading rate (SCLR), the model takes into account a) the hydrolysis of slowly biodegradable compounds in the bulk liquid, and b) the growth of predator microorganisms in the bulk liquid and in the biofilm. The integration of the model and the SCLR allows a general description of the behaviour of COD removal by the MBBR under various conditions. The model is applied for two in-series MBBR wastewater plant from an integrated cellulose and viscose production and accurately describes the experimental concentrations of COD, total suspended solids (TSS), nitrogen and phosphorous obtained during 14 months working at different SCLRs and nutrient dosages. The representation of the microorganism group distribution in the biofilm and in the bulk liquid allow for verification of the presence of predator microorganisms in the second reactor under some operational conditions.

Phytoremediation Tannery wastewater Horizontal subsurface flow Phragmites australis Typha latifolia a b s t r a c t Wastewaters from leather processing are very complex and lead to water pollution if discharged untreated, especially due to its high organic loading. In this study the survival of different plant species in subsurface horizontal flow constructed wetlands receiving tannery wastewater was investigated. Five pilot units were vegetated with Canna indica, Typha latifolia, Phragmites australis, Stenotaphrum secundatum and Iris pseudacorus, and a sixth unit was left as an unvegetated control. The treatment performance of the systems under

A monitoring campaign in a horizontal subsurface flow constructed wetland under the influence of transient loads of flow-rate, organic matter, nitrogen and suspended solids showed an irregular removal of COD and TSS and lower both removal efficiencies and mass removal rates than the ones observed in other studies for similar operating conditions. This circumstance is associated to the presence of large amount of particulate organic matter from non-point sources. The mass removal rate of ammonia increased 39% as both the water and soil temperatures increased from weeks 1–8 to weeks 9–14. A good correlation between mass load and mass removal rate was observed for all measured parameters, which attests a satisfactory response of the bed under to transient loads.

The increasing demand for water in combination with frequent drought periods, even in areas traditionally rich in water resources, puts at risk the sustainability of current living standards. In industrialized countries, widespread shortage of water is caused due to contamination of ground and surface water by industrial effluents, and agricultural chemicals. In many developing countries, industrial pollution is less common, though they are severe near large urban centers. However, untreated or partially-treated sewage poses an acute water pollution problem that causes low water availability. Global trends such as urbanization and migration have increased the demand for water, food and energy. Development of human societies is heavily dependent upon availability of water with suitable quality and in adequate quantities, for a variety of uses ranging from domestic to industrial supplies and Rapid industrialization is adversely impacting the environment globally. Pollution by inappropriate management of industrial wastewater is one of the major environmental problems in India as well, especially with small scale industrial sector in the country. To address the pollution coming out from industries, adoption of cleaner production technologies and waste minimization initiatives are being encouraged. The present case studies on Common Effluent Treatment Plants (CETP) for Textile industry are considered as one of the viable solution for small to medium enterprises for effective wastewater treatment. An effluent treatment plant is operating on physical, chemical and biological treatment method with average waste water in flow of 3MLD has been considered for case study. The wastewater is analyzed for the major water quality parameters, such as Biological Oxygen Demand (BOD),pH, Chemical Oxygen Demand (COD), Total suspended solid (TSS) and Total Dissolved Solids (TDS). The effluent samples were collected on a daily basis for a period of one month. The raw waste water pH was highly alkaline it was then bringing down to neutral which was helpful for chemical and biological treatment. The BOD, COD of the treated effluent reduced significantly, where as very small reduction was observed in dissolved solids. Most of all the parameters were within the permissible limits of Maharashtra Pollution Control Board, India.

In this paper we propose a new statistical method for process monitoring that uses independent component analysis (ICA). ICA is a recently developed method in which the goal is to decompose observed data into linear combinations of statistically independent components . Such a representation has been shown to capture the essential structure of the data in many applications, including signal separation and feature extraction. The basic idea of our approach is to use ICA to extract the essential independent components that drive a process and to combine them with process monitoring techniques. I 2 , I 2 e and SPE charts are proposed as on-line monitoring charts and contribution plots of these statistical quantities are also considered for fault identification. The proposed monitoring method was applied to fault detection and identification in both a simple multivariate process and the simulation benchmark of the biological wastewater treatment process, which is characterized by a variety of fault sources with non-Gaussian characteristics. The simulation results clearly show the power and advantages of ICA monitoring in comparison to PCA monitoring.

Nitrogen (N) cycle involves a complex set of potential biochemical pathways with reactions catalyzed by different microorganisms. Elementary mass balances for COD, DO, NH4-N and alkalinity were conducted and stoichiometric relationships were investigated to explain possible pathways of the nitrogen removal mechanisms in a lab-scale submerged down flow biological packed bed (BPB) reactor. Four sets of experiments were performed by modifying the organic loading and C/N ratio in comparison with steady-state conditions. Approximately 90% of COD and NH4-N removal occurred in two upper sections occupying 1/5 of the reactor height. The elementary
mass balances could not explain all the experimental results with respect to nitrogen removal and oxygen consumption by known mechanisms. The mass balance calculations, excluding the possibility of nitrification, were in general in accordance with the observations indicating no or minimal NO3-N production. The theoretical stoichiometric requirements for nitrification reaction
were satisfied in 6 experiments and in another 8 experiments nitrification may have occurred, but stoichiometry was not satisfied. Using C/N ratio as the variable, only at C/N ratio = 10, the predictions confirmed the possibility of nitrification in the same 3 (out of 4) assays as observed in practice. The results of this study reveal that the nitrogen transformations occurring in the studied reactor are complex and cannot be explained by simple mechanisms of microbial assimilation and nitrification.

ABSTRACT Sewage management in remote rural and mountain areas constitutes a challenge because of the lack of adequate infrastructure and economic capability. Tourism facilities, in particular, possess a special challenge because of huge variability in sewage production and composition as a consequence of variations in number of guests and their activities. Constructed wetlands (CWs) are recognized as a robust and economical ecotechnology capable of meeting these challenges.

This paper was prepared as a part of the undergraduate course offered by Middle East Technical University Department of Environmental Engineering, ENVE 309 "Fundamentals of Biological Treatment", instructed by Prof. Dr. Filiz B. Dilek.
Throughout the text, activated sludge process is explained briefly and anaerobic digestion is investigated in detail.

In recent years considerable effort has been made in the Netherlands toward the development of a more sophisticated anaerobic treatment process, suitable for treating low strength wastes and for applications at liquid detention times of 3-4 hr. The efforts have resulted in a new type of upflow anaerobic sludge blanket (UASB) process, which in recent 6 m3 pilot-plant experiments has shown to be capable of handling organic space loads of 15-40 kg chemical oxygen demand (COD).m-Yday at 3-8 hr liquid detention times. In the first 200 m3 full-scale plant of the UASB concept, organic space loadings of up to 16 kg COD.~n-~/day could be treated satisfactorily at a detention time of 4 hr, using sugar beet waste as a feed. The main results obtained with the process in the laboratory as well as in 6 m3 pilot plant and 200 m3 full-scale experiments are presented and evaluated in this paper. Special attention is given to the main operating characteristics of the UASB reactor concept. Moreover, some preliminary results are presented of laboratory experiments concerning the use of the USB reactor concept for denitrification as well as for the acid formation step in anaerobic treatment. For both purposes the process looks feasible because very satisfactory results with respect to denitrification and acid formation can be achieved at very high hydraulic loads (12 day-') and high organic loading rates, i.e., 20 kg COD.~n-~/day in the denitrification and 60-80 kg C O D~r~/ d a y in the acid formation experiments.

Two bed media were tested (gravel and Filtralite) in shallow horizontal subsurface flow (HSSF) constructed wetlands in order to evaluate the removal of ammonia and nitrate for different types of wastewater (acetate-based and domestic wastewater) and different COD/N ratios. The use of Filtralite allowed both higher mass removal rates (1.1 g NH4–N m2 d1 and 3 g NO3–N m2 d1) and removal efficiencies (>62% for ammonia, 90–100% for nitrate), in less than 2 weeks, when compared to the ones observed with gravel. The COD/N ratio seems to have no significant influence on nitrate removal and the removal of both
ammonia and nitrate seems to have involved not only the conventional pathways of nitrification–denitrification.
The nitrogen loading rate of both ammonia (0.8–2.4 g NH4–N m2 d1) and nitrate (0.6–3.2 g NO3–N m2 d1) seem to have influenced the respective removal rates.

The aim of this study was to investigate the performance of horizontal subsurface flow constructed wetlands planted with Typha latifolia treating tannery wastewater under long-term operation. Two expanded clay aggregates (Filtralite Ò MR3-8-FMR and Filtralite Ò NR3-8-FNR) and a fine gravel-FG were used as substrate for the constructed wetland units plus one unit with FMR was left as an unvegetated control. The systems were subject to three hydraulic loadings, 18, 8 and 6 cm d À1 , and to periods of interruption in the feed. The relationship between the substrate, plant development and removal efficiency, especially of organic matter, was investigated. Organic loadings up to 1800 kg BOD 5 ha À1 d À1 and 3849 kg COD ha À1 d À1 were applied leading to mass removals of up to 652 kg BOD 5 ha À1 d À1 and 1869 kg COD ha À1 d À1 , respectively. The three different substrates were adequate for the establishment of T. latifolia, although the clay aggregates allowed for higher plant propagation levels. The units with FNR and FMR achieved significantly higher COD and BOD 5 removal when compared to the FG and to the unplanted units. The systems proved to be tolerant to high organic loadings and to interruptions in feed suggesting this technology as a viable option for the biological treatment of tannery wastewater.

This paper reviews the development and evolution of anaerobic reactor for wastewater treatment. The successful application of anaerobic technology to the treatment of industrial wastewater is critically dependent on the development and type of anaerobic reactor used. Since the original design was developed, many modifications have been made in reactor design in order to enhance both the efficiency and reliability of the reactor. In this paper, the main alteration and modifications of anaerobic reactor would be documented.

A submerged biologicalaeratedfilter (BAF) partiallyaerated was used to study the removal of lowconcentrations of ammonia nitrogen (0.3 g N/m3 to 30.5 g N/m3) typically found in nutrient enriched river and lake waters, and treated effluents. Four series of experiments were performed with a synthetic wastewater at ammonia loading rates between 6 g N/m3 d and 903 g N/m3 d and C/N ratios from 2 to 20. The results showed that ammonia removal rates reached higher values (172 g N/m3 d to 564 g N/m3 d) for C/N = 2 and lower values (13.6 g N/m3 d to 34.6 g N/m3 d) for C/N = 20. Between 50% and 70% of the ammonia was removed in the upper section of the BAF, where the dissolved oxygen (DO) concentration was over 2.1 g O2/m3 and the biofilm depth ranged from 0.4 to 0.6 mm. At the bottom section of the reactor, simultaneous removal of ammonia and nitrate was observed at the DO concentrations in the range 0.4 g O2/m3 to 0.8 g O2/m3. There was no removal of ammonia nitrogen for loads below 15 g N/m3.d. The results indicate that the removal of nitrogen in partiallyaerated BAF may not only be explained by the conventional mechanisms of nitrification/denitrification.

This article provides the methane yield of municipal solid waste and its main constituents using the biochemical methane potential (BMP) test. The methane yield of kitchen waste (KW), paper waste (PW), and garden waste (GW) were 357 ( -24.7), 147 ( -17.1), and 114 ( -0.6) mL CH 4 /g VS, respectively. The hydrolysis constant in the first order kinetic model was 0.25, 0.095, and 0.121 d -1 for KW, PW, and GW, respectively. The effect of the inoculum to substrate (I/S) ratio in the BMP test was investigated. Methane yields of 297.4 ( -18.6), 293.5 ( -33.9), and 378.2 ( -10.3) mL CH 4 /g VS were found at I/S ratios of 1.4, 7.2, and 12.9, respectively, whereas the hydrolysis constants were 0.112, 0.151, and 0.221 d -1 . A new method based on the production of soluble chemical oxygen demand (SCOD) while selectively inhibiting methanogenesis has been used to determine the hydrolysis constant (0.25 d -1 ) according to its true definition, which is the conversion of particulate COD to SCOD, showing that the method based on methane evolution can underestimate the actual value when hydrolysis is not the rate-limiting step.

The raising pharmaceutical industrial wastewater (PIW) is one of the major health problems nowadays, not only for aquatic life but also for human beings and the environment. Several conventional techniques including coagulation, filtration, biological membranes and advanced oxidation have been used for the treatment of PIW, however, all of these techniques are limited with their applications and results. The present study aimed to build a cost-effective, high biodegradable, eco-friendly and highly efficient PIW treatment technique to generate electricity and reduce the COD of wastewater simultaneously. A novel paraboloid shaped graphite-based microbial fuel cell (MFC) configuration has been designed by eliminating different types of casings and membranes for bio-electrogenesis and treatment of PIW. Municipal solid wastewater (MSW) was used as a substrate for developing the biofilm in paraboloid graphite-based MFC. The PIW treatment showed adequate bioelectricity generation including; current, power, voltage and open-circuit voltage (OCV) of about 2.76 mA, 0.76 mW, 276 mV and 330 mV at 100 Ω respectively after five operating cycles. The cyclic voltammetry showed the maximum generation of 2.01 W/m3 and 168 mA/m2 of power and current densities respectively followed by a considerable reduction in internal resistance from 197 to 99 Ω. The results reported a significant amount of reduction in COD (80.55%) and TDS (35.62%) for PIW by MFC respectively. The reduction in the percentage removal efficiency of COD (80.55%) suggested that the removal of organic compounds from PIW is parallel to bioelectrogenesis. Based on these major findings the novel membrane-less and paraboloid graphite-based MFC operation significantly drag concentration towards the feasibility of using pharmaceutical wastewaters for bio-electrogenesis.

In the summer of 2003, a microalga strain was isolated from a massive green microalgae bloom in wastewater stabilization ponds at the treatment facility of La Paz, B.C.S., Mexico. Prevailing environmental conditions were air temperatures over 40°C, water temperature of 37°C, and insolation of up to 2400 lmol m 2 s À1 at midday for several hours at the water surface for four months. The microalga was identified as Chlorella sorokiniana Shih. et Krauss, based on sequencing its entire 18S rRNA gene. In a controlled photo-bioreactor, this strain can grow to high population densities in synthetic wastewater at temperatures of 40-42°C and light intensity of 2500 lmol m 2 s À1 for 5 h daily and efficiently remove ammonium from the wastewater under these conditions better than under normal lower temperature (28°C) and lower light intensity (60 lmol m 2 s À1 ). When co-immobilized with the bacterium Azospirillum brasilense that promotes growth of microalgae, the population of microalga grew faster and removed even more ammonium. Under exposure to extreme growth conditions, the quantity of four photosynthetic pigments increased in the co-immobilized cultures. This strain of microalga has potential as a wastewater treatment agent under extreme conditions of temperature and light intensity.

Fluoride is a common contaminant in a variety of industrial wastewaters. Available information on the potential toxicity of fluoride to microorganisms implicated in biological wastewater treatment is very limited. The objective of this study was to evaluate the inhibitory effect of fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in wastewater treatment processes. The results of short-term batch bioassays indicated that the toxicity of sodium fluoride varied widely depending on the microbial population. Anaerobic microorganisms involved in various metabolic steps of anaerobic digestion processes were found to be very sensitive to the presence of fluoride. The concentrations of fluoride causing 50% metabolic inhibition (IC 50 ) of propionate-and butyrate-degrading microorganisms as well as mesophilic and thermophilic acetate-utilizing methanogens ranged from 18 to 43 mg/L. Fluoride was also inhibitory to nitrification, albeit at relatively high levels (IC 50 ¼ 149 mg/L). Nitrifying bacteria appeared to adapt rapidly to fluoride, and a near complete recovery of their metabolic activity was observed after only 4 d of exposure to high fluoride levels (up to 500 mg/L). All other microbial populations evaluated in this study, i.e., glucose fermenters, aerobic glucose-degrading heterotrophs, denitrifying bacteria, and H 2 -utilizing methanogens, tolerated fluoride at very high concentrations (>500 mg/L). (R. Sierra-Alvarez).

This study was on the technical and biological characteristics of a partial-SHARON submerged-filter bioreactor of 3 L. The main focus was the influence of the hydraulic retention time (HRT) on biofilms. For this purpose, we used molecular tools based on the partial 16S rRNA genes. The results showed that the HRT may affect the nitrification processes of a bioreactor using synthetic
wastewater containing 600 mg/L of ammonia. It was found
that an HRT of 0.5 day transformed 100 % of the ammonium
into nitrite. However, when the HRT was decreased to 0.4 day, there was a significant reduction (35 %) in the quantity of ammonia transformed, which confirmed the complexity of the system operation. Moreover, a PCRTGGE approach highlighted the differences observed. The results obtained showed that an HRT of 0.5 day reduced bacterial biodiversity in the biofilms, which were mainly formed by Nitrosomonas and Diaphorobacter. In contrast, an HRT of 0.4 day facilitated the formation of heterogeneous biofilms formed by nitrifying bacteria, such as Nitrosomonas sp., Nitrosospira sp., and Nitrosovibrio sp.).

The control of pollution has been a major concern in recent times. Textile dyes which are important organic compounds are also significant industrial pollutants. Textile dyes are commonly xenobiotic in nature and are not degraded easily by biological systems.

This paper presents an example of the importance of evapotranspiration in constructed wetlands, with vertical subsurface flow, comparing different methods of treatment efficiency calculations and discussing the influence of evapotranspiration on removal rates. The application of reed, marked by high transpiration ability, is a cheap and effective method of landfill leachate disposal. A 2-year study examined the effectiveness of leachate treatment in constructed wetlands with reed. Two kinds of vertical subsurface flow systems: first with sand, and second with combined two layers of sewage sludge and sand has been tested. 1, 3, and 5 mm d −1 hydraulic loading rates of landfill leachate have been applied. Daily evapotranspiration was in the range from 0.98 to 2.99 mm d −1 in the first year of research and from 2.56 to 4.61 mm d −1 in the second year. The influence of evapotranspiration rate on chemical oxygen demand (COD) removal rate was examined. Two methods of removal efficiency calculation have been used: first based on inlet and outlet COD concentrations, second on mass balance determination. Research showed that the removal efficiency calculated as a comparison between initial and final concentration is significantly lower, than expected from mass balance, especially, when higher hydraulic loading rates were applied.