73,815 research outputs found
The Comparison of parasite eggs and protozoan cysts of urban raw wastewater and efficiency of various wastewater treatment systems to remove them
One of the most important quality characteristics associated with wastewater reuse in agriculture is the microbial quality. This study aimed to determine the efficiencies of Ghasreshirin (constructed wetland), Islamabadgharb and Gilangharb wastewater treatment plants (stabilization ponds), Sarpolezahab and Paveh (extended aeration activated sludge) and Kermanshah (conventional activated sludge) in the removal of protozoan cysts and parasitic eggs.
This study was carried out during six months and samples were collected at weekly intervals from influent and effluent of the wastewater plants. In order to determine the concentration of ova, 288 samples were analyzed by Mc Master Slide according to Bailenger method.
No parasite eggs or protozoan cysts were detected in the effluents of the constructed wetland or stabilization ponds systems. The extended aeration activated sludge system of Sarpolezahab removed 99-100% of parasite eggs and ≥99% of protozoan cysts. The respective values for extended aeration activated sludge system of Paveh were 97.5-100% and ≥99%. However, the conventional activated sludge of Kermanshah removed 97-99% and 99-100% of parasite eggs and protozoan cysts, respectively.
According to the results, removal efficiency for cysts and parasite eggs in natural systems (constructed wetland and stabilization ponds) is better than mechanical systems (extended aeration activated sludge and conventional activated sludge). The effluent quality of all systems in terms of nematode eggs is consisted to Engelberg index (nematode eggs count: 1 ≥ counts per liter)
Fate and occurrence of alkylphenolic compounds in sewage sludges determined by liquid chromatography tandem mass spectrometry
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2009 Taylor & Francis.An analytical method has been developed and applied to determine the concentrations of the nonionic alkylphenol polyethoxylate surfactants and their metabolites, alkylphenoxy carboxylates and alkyphenols, in sewage sludges. The compounds were extracted with methanol/acetone (1:1 v/v) from sludge, and concentrated extracts were cleaned by silica solid‐phase extraction prior to determination by liquid chromatography tandem mass spectrometry. The recoveries, determined by spiking sewage sludge at two concentrations, ranged from 51% to 89% with method detection limits from 6 µg kg−1 to 60 µg kg−1. The methodology was subsequently applied to sludge samples obtained from a carbonaceous activated sludge plant, a nitrifying/denitrifying activated sludge plant and a nitrifying/denitrifying activated sludge plant with phosphorus removal. Concentrations of nonylphenolic compounds were two to three times higher than their octyl analogues. Long‐chain nonylphenol polyethoxylates (NP3–12EO) ranged from 16 µg kg−1 to 11754 µg kg−1. The estrogenic metabolite nonylphenol was present at concentrations ranging from 33 µg kg−1 to 6696 µg kg−1.Public Utilities Board of Singapore, Thames Water and Yorkshire Water
Effect of Activated Sludge Preservation on Its Adsorption Capacity in Treatment of Wastewater
Adsorption by activated sludge which plays a significant role in substrate removal has received a lot of recognition. A number of studies have been conducted into understanding this mechanism. However, the impact of activated sludge preservation on the adsorption capacity test results has not been documented. Live activated sludge is usually preserved after sampling to maintain the original sludge characteristics in order not to alter its adsorption capacity. Preservation of the sludge is relevant when the sludge has to be transported over long distances before adsorption experiments can be conducted. This paper seeks to present the effects of preservation of activated sludge on its adsorption capacity. The preservation methods considered were pre-aeration and cold-storage of the sludge. Sludge samples were pre-aerated for periods of 4 and 24 hours at room temperature and some were stored at 4?C for 6 hours. Adsorption batch experiments were then carried out on both fresh and preserved activated sludge samples. Glucose was used as an external substrate in these experiments. The results revealed a difference between the adsorption capacity of the fresh and preserved sludge samples. Sludge pre-aeration increased the adsorption capacity of the sludge. There was however, no significant difference in the adsorption capacities for 4h and 24h pre-aerated sludge samples. Adsorption capacity of the 6h cold-stored activated sludge was poor compared to that of the fresh sludge. Keywords: Activated sludge, Activated sludge preservation, Adsorption capacity, Glucos
Standardization of activated sludge for biodegradation tests
Activated sludges are an inoculum source commonly used in biodegradation studies, as wastewater treatment facilities constitute an entry point to the environment for many chemicals. In this paper, the main issues relating to the use of activated sludge in biodegradability tests are presented. Special attention is also devoted to discussing the factors affecting both the activity of the microbial communities and the test results. After a short survey of the state of the art of microbiology of activated sludge, the paper focuses on the methods used to reduce the variations in the diversity, quality and quantity of these communities. Finally, use of surrogates as reference materials in biodegradability tests is discussed
The Effects of Enzymes on Activated Sludge Floc
Dialysed activated sludge was used as a substrate to test for enzymes which can hydrolyse activated sludge floc. Two hundred and fifty aerobic and anaerobic microorganisms were tested against activated sludge for the presence of hydrolytic enzymes. These included known genera and organisms obtained by various enrichment procedures. Anaerobic digester mixed liquor was contacted with activated sludge agar under anaerobic conditions. None of the microorganisms present in the digester liquor hydrolysed the floc. The following commercial enzymes were contacted with activated sludge singly, in combination, and sequentially under various physical and chemical conditions: protease, lipase, cellulose, pectinase, phospholipase C, trypsin, and glucuronidase. Although commercial enzymes and various microorganisms reacted with known substrate controls neither the enzymes nor microorganisms employed affected the activated sludge floc. Treatment of activated sludge floc with ethylenediaminetetraacetic acid resulted in gross deflocculation and release of humic substances. The floc particle, probably a combination of polymers bound in a complex manner, is resistant to enzymatic degradation. Several workers have reported on the enzymatic hydrolysis of polymers produced by axenic cultures isolated from activated sludge floc. It is unlikely that the results of their work can be extrapolated to the complex structure of activated sludge floc particles
Vrishabhavathi Valley Wastewater Treatment Plant System Upgrade
Sixteen activated sludge tanks, eight secondary clarifiers, and four return pump stations were designed for the Vrishabhavathi Wastewater Treatment plant in Bangalore India. The design included tank dimensions, mechanical equipment associated with each component, pipe sizes for the piping system, and a cost estimate with a construction schedule. The activate sludge tanks were designed to be made of reinforced concrete with a mechanical air diffuser system installed for oxidation purposes. The secondary clarifiers were designed using reinforced concrete and a mechanical sweeping mechanism to scrape up the sludge as it settles to the bottom of the tank. Return pump stations were designed to transport the sludge into recirculation pipes or to a waste activated sludge stream. The treated water from the expanded facility will be discharged back into the river or transported to a tertiary treatment facility on site. The effluent will act as a source of non-potable water for local urban and agricultural use. Construction of the proposed facility will not interfere with the operation of the existing plant. This expansion to the existing facility will provide the city of Bangalore with an additional 71.33 million gallons per day of fresh, not-potable water
A Comparative Study of the Effects of External Selection on Settleability and Formation of Aerobic Granular Sludge
Aerobic granular sludge (AGS) has shown much promise in the advancement of the wastewater treatment industry. AGS has been studied intensely since the early 1990’s due to highly desirable characteristics of nutrient removal efficiency, low footprint, and abnormally faster settling rates than conventional activated sludge. With the exception of a few on-going research projects, all AGS systems have been studied and implemented through the use of sequencing batch reactors (SBR). Recently, a novel approach to developing AGS and improving settling characteristics of activated sludge within conventional activated sludge (CAS) processes has being attempted through the use of external selection.
Activated sludge was fed to a hydrocyclone for approximately 374 days to select for denser material that would improve settling and potentially cultivate AGS. The effect of the hydrocyclone on the activated sludge was directly compared to the settling characteristics of an identical parallel treatment train that did not utilize the external selector. Data suggests that with the correct nozzle and operating pressure, much of the faster settling sludge and ballast material for the cultivation of AGS can be selected for, retained, and returned to the activated sludge process. During the warmer months, while the wastewater temperature was consistently \u3e19ᵒC, the hydrocyclone improved settling rates in the activated sludge by up to 15-20x the settling rates of the activated sludge in the parallel train.
While a shift to granulation did not occur, further research and optimization could potentially lead to the cultivation of AGS and the further improvement of settling characteristics of activated sludge. The settling performance imparted on the activated sludge by the hydrocyclone shows that it is feasible to improve the overall settleability of activated sludge in a suspended growth process through external selection
Synergistic co-cultivation of activated sludge and microalgae in enhancing lipid production and N-laden wastewater treatment
The influence of inoculation ratios of activated sludge and microalgae were investigated in this study in the aspects of biomass yield, lipid yield and total nitrogen (TN) removal efficiency. It was observed that mixed culture of activated sludge/microalgae with the ratio 1:1 and 1:0.75 achieved a maximum lipid production up to 0.144 g/L and 0.133 g/L as compared with microalgae culture alone, which was only 0.081 g/L. The highest total nitrogen (TN) removal was observed with 1:1 and 1:0.75 ratios of activated sludge/microalgae cultures ranging from 96.3-96.9% removal efficiency, which was an improvement of about 90% removal efficiency compared to the activated sludge culture (6.25±0.08%). The flocculation efficiency was generally improved in mixed cultures of activated sludge andmicroalgae in comparison with only activated sludge culture and microalgae culture alone.Keywords: activated sludge; microalgae; co-cultivation; lipid; nitrogen removal
Activated Sludge as Renewable Fuels and Oleochemicals Feedstock
The utilization of activated sludge as feedstock for biofuel and oleochemical production was investigated. Initial studies included optimization of biodiesel production from this feedstock through in situ transesterification. Results of these studies indicated that activated sludge biodiesel is not economically viable. This was primarily due to relatively low yields and the high economics of feedstock dewatering. Strategies to increase biofuel yield from activated sludge were then evaluated. Bacterial species present in activated sludge are known to produce a wide variety of lipidic compounds as carbon and energy storage material and as components of their cellular structures. In addition to lipidic compounds, activated sludge bacteria might also contain other compounds depending on wastewater characteristics. Among these bacterial compounds, only the saponifiable ones can be converted to biodiesel. The unsaponifiable compounds present in the activated sludge are also important, not only for biofuel production, but also for a wide variety of applications. Characterization of lipids in activated sludge revealed that it contains significant amount of polyhydroxyalkanoates, wax esters, acylglycerides and fatty acids. It also contains Template Created By: James Nail 2010 sterols, steryl esters and phospholipids as well as small but detectable amounts of hydrocarbons. This indicated that activated sludge could be also an inexpensive source of oleochemicals. Another strategy that was evaluated was lipid-enhancement by fermentation of activated sludge. Since the majority of products from petroleum oil are used as transportation fuel, the aim here was to increase the saponifiable lipids in activated sludge bacteria by applying a biochemical stimulus (i.e. high C:N ratio). Results showed that application of this stimulus increased the amount of saponifiable lipids, particularly triacyglycerides, in the activated sludge. Furthermore, fermentation homogenized the lipids in the sludge regardless of its source. This solidified the concept of utilizing wastewater treatment facilities as biorefineries. To support the utilization of other compounds in raw activated sludge for biofuel production, a model compound was chosen for catalytic cracking experiments. Results indicated that catalytic cracking of 1-octadecanol over H+ZSM5 proceeds via dehydration, producing octadecene. The octadecene then undergoes a series of reactions including β-C─C bond scission, alkylation, oligomerization, dehydrocyclization and aromatization producing aromatics, paraffins and olefins suitable for fuel applications
Diversity and dynamics of Archaea in an activated sludge wastewater treatment plant
BACKGROUND: The activated sludge process is one of the most widely used methods for treatment of wastewater and the microbial community composition in the sludge is important for the process operation. While the bacterial communities have been characterized in various activated sludge systems little is known about archaeal communities in activated sludge. The diversity and dynamics of the Archaea community in a full-scale activated sludge wastewater treatment plant were investigated by fluorescence in situ hybridization, terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes. RESULTS: The Archaea community was dominated by Methanosaeta-like species. During a 15 month period major changes in the community composition were only observed twice despite seasonal variations in environmental and operating conditions. Water temperature appeared to be the process parameter that affected the community composition the most. Several terminal restriction fragments also showed strong correlations with sludge properties and effluent water properties. The Archaea were estimated to make up 1.6% of total cell numbers in the activated sludge and were present both as single cells and colonies of varying sizes. CONCLUSIONS: The results presented here show that Archaea can constitute a constant and integral part of the activated sludge and that it can therefore be useful to include Archaea in future studies of microbial communities in activated sludge
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