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The oxic-settling-anoxic (OSA) system operated as a sequencing batch reactor was studied. Sludge was interchanged between the aerobic and anaerobic reactors, and the number of daily interchange times was changed from 1 to 4 during the experiments. When the sludge was interchanged 1 time/d, the reduction of excess sludge mass was only 52.8%. When the sludge was interchanged 4 times/d, the reduction of excess sludge mass was 77.4%; reductions in the total chemical oxygen demand, total solids, and total volatile solids of both the anaerobic sludge and the aerobic settled sludge were the greatest; and more soluble iron was released from the anaerobic sludge. The water quality of the final effluent in the two systems was close. The investigation showed that interchange times are important in improving sludge reduction efficiency, and the parameter should be regarded as an important operating factor in the OSA process. [ABSTRACT FROM AUTHOR]

It was found that aerobic strategies combined with multiple nutrient limitations produced greater quantities of polyhydroxyalkanoates (PHAs) than strategies relying on oxygen limitation (either microaerophilic or anaerobic/aerobic). This was true both for a synthetic wastewater composed of acetic and propionic acid, and also for a nutrient deficient industrial wastewater. PHA/substrate yields were shown to be comparable to axenic systems for many operating strategies analyzed, and it was found that PHA composition could be affected by process operational conditions. The molecular weight and melting point of the PHA produced were found to be in a desirable range with respect to material properties, which have not been well studied in the previous literature for mixed cultures (Salehizadeh and Van Loodsrecht, 2004). The effects of process staging, multiple treatment cycles, and inocula source were also addressed. [ABSTRACT FROM AUTHOR]

Improved design strategies at BNR plants should include cost reductions so that the consumers and water authorities will be more willing to build EBPR plants instead of conventional activated sludge plants. Through efficient design, actual savings in construction and operation costs can be realized. For this reason, anaerobic stabilization of COD needs to be seriously considered during design for direct energy savings at the plants. The existence of anaerobic stabilization has been demonstrated through experimental work. Evaluation of operational data from existing plants has also indicated the definite presence of anaerobic stabilization at plants that include anaerobic zones for EBPR as part of their operation. By exploring the biochemical reactions taking place in EBPR process, particularly the involvement of the storage mechanisms for PHA, poly-P and glycogen storage, the potential mechanisms of the anaerobic stabilization of COD in EBPR systems was explored. The resultant balances pointed out the importance of glycogen metabolism in terms of conserving carbon and providing a sink for the reducing equivalents produced under aerobic conditions. This mechanism is different from those observed in anoxic-aerobic and conventional aerobic activated sludge systems, and appears to be at least partially responsible for the observed anaerobic stabilization of COD. [ABSTRACT FROM AUTHOR]

In this paper, the performance of the Tyson Foods wastewater treatment plant with an average flow rate of 6500m³/d was evaluated before and after upgrading of the treatment system for nitrogen removal. This study was also covered with an additional recommendation of BIOWINTM BNR program simulation after the modification period to achieve an additional nutrient removal. The results clearly show that the upgrading was very successful for improved nitrogen removal, with a 57% decrease on the total nitrogen discharge. There also were slight reductions in the discharged loads of biological oxygen demand, total suspended solids, ammonium and total phosphorus with denitrification, even though the effluent flow was higher during operation of the nitrogen removal configuration. [ABSTRACT FROM AUTHOR]

The study was designed to investigate the effects of temperature and phosphorus limitation on polyhydroxyalkanoate (PHA) production and storage by activated sludge biomass. The two-stage operation approach, i.e. a growth phase followed by a nutrient limitation phase, was applied to induce PHA accumulation. The pre-selected temperatures of 10, 20 and 30°C were investigated under phosphorus limitation conditions using three four-litre fully aerobic SBR systems operated at an SRT of 10 days with cycle time and HRT of 6 and 10 hours. PHA production was greater in the 10°C system than in the 20°C and 30°C systems but there was little difference between the two higher temperatures. The maximum PHA fractions of the sludge were 52, 45 and 47%TSS for the three temperatures from low to high, and the maximum PHA concentrations in the mixed liquors were 1,491, 1,294 and 1,260 mg/l, respectively. However, it was observed that very low values of PHA yield per unit COD consumed were obtained, i.e., 0.05, 0.03 and 0.04 mgPHA/mgCODu, for the 10, 20 and 30°C reactors, respectively. This was because all three systems required several days to reach maximum PHA accumulation in their mixed liquor biomasses. It is probable the bacteria still had some stored poly-P in their cells upon initiation of the phosphorus limited influent, and PHA accumulation was delayed until the stored phosphorus was depleted. Also, PHA productivity was reduced by the large amounts of biomass lost from the systems because of sludge bulking. [ABSTRACT FROM AUTHOR]

This article evaluates effects of pH and substrate on the competition between glycogen (GAOs) and phosphorus accumulating organisms (PAOs). A sequencing batch reactor system was operated for enhanced biological phosphorus removal (EBPR) with acetate as the sole carbon source and acetate added domestic wastewater at different influent acetate/phosphate ratios. Some batch tests were performed using acetate added domestic wastewater at different influent acetate/phosphate ratios, with different initial pH values of acetate and domestic wastewater mixture. The resulting experimental data supported the presence of GAOs for all tested HAC/P ratios, especially under P limiting conditions for acetate as sole carbon source. Strong evidence is observed that acetate added domestic wastewater system had higher PAOs fraction than acetate system as sole source carbon, with using model components, namely substrate uptake, glycogen utilization and P release. [ABSTRACT FROM AUTHOR]

Because adequate nutrient controls were not established in the USA and other countries when there were past opportunities to do so, nutrient pollution of estuaries and coastal waters has resulted in the impairment of ecosystems and major reductions or collapse of fisheries at numerous sites around the world, resulting in major economic and societal impacts. The root problem is that political policies and processes have permitted municipalities, developers, industries and farmers to expand and operate without paying the full cost of their activities. Their expanded activities have occurred at the expense and displacement of those who rely on the productivity and recreational value of our estuarine and coastal waters. Some governments have developed remedial nutrient control programs, but most of them have been poorly conceived, under funded and inadequately enforced, resulting in small increments of progress that tend to be lost because of inadequate land use and immigration controls. It is proposed that establishment of comprehensive nutrient controls is needed throughout the world to preserve and protect estuarine and coastal waters, and to protect or re-establish fisheries, for both economic and societal stability. Nitrogen is the key nutrient for the establishment of control strategies. It is recommended that nutrient recovery from wastewaters and controlled reuse of both water and nutrients be widely implemented as a part of nutrient control strategies. [ABSTRACT FROM AUTHOR]

The Wilderness Wastewater Treatment Plant (WWTP) located in Orange County, Virginia is a four concentric ring oxidation ditch activated sludge system with a rated capacity of 1,935 m³/day. The three outer rings are used for wastewater treatment and the inner ring is used as an aerobic digester. The flow capacity has been increased from 1,935 to 3,760 m³/d, however, the desired design capacity has since been increased to 3,870 m³/d, and there are plans to eventually expand to approximately 4,840 m³/d with improved nitrogen removal. The design goal for the planned upgrade is to discharge an effluent that contains less than 10 mg/l total nitrogen (TN) at all times, with an annual average of 8 mg/l or less. In this study, the pre-upgrade performance of the Wilderness Wastewater Treatment Plant was evaluated and several modifications were recommended for the incorporation of biological nutrient removal (BNR). [ABSTRACT FROM AUTHOR]

Recent developments will strongly influence the design and utilization of small wastewater treatment systems in the future, e.g. population increases in non-sewered rural areas and developing countries; increasing impairment of surface water quality; the construction of occupied high-rise buildings in metropolitan areas; the development of planned but somewhat isolated communities, growing shortages of water that mandate reuse of wastewaters. It is well known that there is a very strong linkage between wastewater disposal methods in rural areas and developing countries and the general health of the population. These problems could be greatly reduced or prevented by the utilization of well known excreta disposal and small wastewater treatment system technologies, but the development of more innovative onsite systems is needed. It is expected that future environmental and public health pressures in developed countries will require increasingly stringent effluent limitations for small and on-site wastewater disposal systems, based primarily on nutrient discharges. Both on-site and small-scale technologies are available for the more stringent requirements, but innovative and more economical designs are needed for wide-spread acceptance. Water reuse should be a consideration for the designs of these systems. Implementation and utilization of well known technologies are needed, but the obstacles are often more social and political than economical. [ABSTRACT FROM AUTHOR]

Because adequate nutrient controls were not established when there were past opportunities to do so, nutrient pollution of estuaries and coastal waters has resulted in the impairment of ecosystems and major reductions or collapse of fisheries at numerous sites around the world, resulting in major economical and societal impacts. The root of the problem is that the political policies and processes have permitted municipalities, developers, industries and farmers to expand and operate without paying the full cost of their activities, and this has been done at the expense of those who rely on the productivity and recreational value of our estuarine and coastal waters. Some governments have developed remedial nutrient control programs, but most of them have been under funded and inadequately enforced, resulting in small increments of progress that tend to be lost because of inadequate land use and immigration controls. It is believed that nutrient recovery and controlled reuse can provide a major tool for the control of nutrient pollution and should be widely implemented. Plans are currently being developed to promote widespread use of nutrient recovery and reuse in the Chesapeake Bay region of the USA. An example of phosphorus reuse is presented. [ABSTRACT FROM AUTHOR]

The objectives of the study described in this paper were to study the requirements of potassium, magnesium, and calcium for enhanced biological phosphorus removal (EBPR) and to determine whether either potassium or magnesium could support EBPR on its own. Batch experiments indicated that phosphorus uptake by the sludge was affected by the availability of potassium, magnesium, and calcium. Both potassium and magnesium were simultaneously required and neither was adequate by itself for EBPR. Calcium did not appear to be required for EBPR, and did not seem to be involved in biologically mediated chemical precipitation. [ABSTRACT FROM AUTHOR]

An investigation comprising four studies was undertaken to determinepossible factors affecting the growth of several different types of filamentous microorganisms present in a bulking industrial wastewateractivated sludge. Results from laboratory-scale continuous-flow and full-scale studies suggested that DO concentration and F:M ratio werethe likely key factors affecting filamentous growth in the activatedsludge. From the results of two laboratory studies isolating the effects of DO concentration and F:M ratio on filamentous growth, favorable growth ranges of DO concentration or F:M ratio were estimated for the following filaments: Microthrix parvicella, Nocardia spp., Nostocoida limicola II, and Types 0041, 1851, and 1863. Most of the bacteria causing filamentous bulking of the activated sludge were found to be filaments typically associated with low F:M, and increasing the F:Mratio appeared to cause N. limicola II to lose its competitive advantage in the activated sludge system. Type 1863, on the other hand, was found to be a low DO filament, as DO concentrations of 0.1 mg O2/l or less appeared to be a necessary condition for its filamentous growth. Though Nocardia was found to be a low F:M filament, its growth also seemed to be affected by DO concentration, as its growth was stimulated by concentrations of 1.0 mg O2/l or greater, with a near linear relationship up to at least 5 mg O2/l. ) 1998 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]