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Secagem térmica de lodos de esgoto: determinação da umidade de equilíbrio. / Thermal drying of wastewater sludge: determination of equilibrium moisture.David, Airton Checoni 25 April 2002 (has links)
O estudo apresenta os principais aspectos da operação de secagem térmica de lodos gerados em estações de tratamento de esgotos, os tipos de equipamentos disponíveis no mercado que podem ser utilizados para esse fim e o comportamento da sorção de umidade pelo material seco quando em contato com o ar ambiente. A operação de secagem térmica é uma alternativa para a diminuição do peso e volume de lodos, com conseqüente diminuição dos custos de transporte e disposição final. É considerada, também, um processo de melhoria da qualidade do lodo, pois elimina os microrganismos patogênicos e, ao mesmo tempo, preserva a matéria orgânica presente no lodo, aspectos de importância fundamental quando o lodo/biossólido seco vai ser utilizado na agricultura. Os equipamentos para secagem térmica podem ser diretos ou indiretos. Os principais tipos são: secador rotativo, de soleiras múltiplas, de leito fluidizado, por transporte pneumático e transportadores de esteira. Cada tipo possui vantagens e desvantagens em relação aos demais. A eficiência do processo de secagem térmica é influenciada por uma série de fatores, como: consumo específico de energia, tipo de equipamento utilizado e teores de umidade inicial e final do material. Nos ensaios de laboratório, mediu-se os teores de umidade de equilíbrio do lodo produzido na ETE Baureri, localizada na Região Metropolitana de São Paulo, sob diferentes condições de umidade relativa do ar ambiente. Com esses valores, obteve-se a curva de umidade de equilíbrio do material. Como resultado dessa experiência conclui-se que para cada umidade relativa do ar ambiente há um teor de umidade de equilíbrio do lodo. / The study presents the main aspects of a thermal drying operation of the sludge produced by wastewater treatment plants, the types of equipment likely to be used for this purpose and the sorption behavior of the water contents by the dry material when in contact with the air. The thermal drying operation is an alternative to reduce the weight and volume of the sludge production with a resulting decrease in transportation and final disposal costs. It is also deemed to be a process that improves the sludge quality because includes the elimination of pathogenic microorganisms while preserving the existing organic matter of the sludge, which are aspects of the utmost importance whenever the dry biosolid will be used as fertilizer in agriculture. The thermal drying equipment can be direct or indirect. The main types are: rotary dryers, multi-tray dryers, fluid bed dryers, flash dryers, and conveyor dryers. Each type presents advantages and disadvantages when compared to one another. The efficiency of the thermal drying process is affected by several aspects, such as specific consumption of energy, type of equipment used, and initial and final water contents of the material. The laboratory tests measured the equilibrium moisture contents of the sludge produced by Barueri Wastewater Treatment Plant, located in the São Paulo Metropolitan Region, under different conditions of environment relative humidity. Based on these measurements, an equilibrium moisture curve of the material was obtained. The major conclusion of the experiment was that to each environment relative humidity there is a corresponding equilibrium moisture of the sludge.
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Parameter uncertainty and modeling of sludge dewatering in one dimensionPlaskett, Joseph H. 01 January 1992 (has links)
Separation of liquid from solids is a necessary step in the ultimate disposal of wastewater sludges. Most commonly, sludges are dewatered by pressure-filtration methods. Mathematical models of the physics of the sludge dewatering process would provide the ability to predict dewatering performance and optimize the design and operation of dewatering facilities.
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Winter wheat response to nitrogen, phosphorus, sulfur, and zinc supplied by municipal biosolidsShearin, Todd E. 22 September 1999 (has links)
Graduation date: 2000
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Determination of fluorinated alkyl substances in aqueous systemsSchultz, Melissa M. 09 December 2004 (has links)
Fluorinated alkyl substances, which can be persistent, toxic, and
bioaccumulative, have been quantitated in many densely populated and
remote regions, including in air, surface waters, groundwater, and biota;
however, little is known about their transport or behavior in the environment.
Wastewater effluent is one of the principal routes for introducing environmental
contaminants into aquatic environments. The partitioning behavior of
fluorinated alkyl substances between aqueous and particulate phases is not
well characterized; thus, sorption onto sludge can be a removal mechanism of
fluorinated alkyl substances from the wastewater stream. This is another
route into the environment if the biosolids are land-applied.
In an attempt to analyze for the fluorinated alkyl substances in
wastewater, known aqueous-film-forming-foam (AFFF)-laden groundwater
sampled from 3 military bases was used to develop an assay using liquid
chromatography (LC), electrospray ionization (ESI) tandem mass spectrometry (MS/MS). While working on the method development,
fluorotelomer sulfonates were detected at Wurtsmith AFB, MI, and Tyndall
AFB, FL, where total fluoroatkyl sulfonates ranged respectively from below
quantitation (���0.60 ��g/L) to 182 ��g/L and from 1100 ��g/L to 14,600 ��g/L.
The LC ESI-MS/MS method was modified to quantitate fluorinated alkyl
sulfonates in wastewater by incorporating a htgh volume sample loop (500
��L), which lowered detection and quantitation limits by at least a factor of 50.
This method was applied to 24 h composites of influents and effluents
collected from treatment plants distributed nationwide. Fluorinated alkyl
substances were observed at all 10 plants sampled, and each wastewater
treatment plant was found to have a unique distribution of fluorinated alkyl
substances, despite similar treatment processes. In 9 out of the 10 plants
sampled, at least one class of fluorinated alkyl substance exhibited significant
increases in the effluent as compared to the influent levels.
The high-volume-injection LC ESI-MS/MS method was also used to
monitor the mass flows of perfluoroalkyl sulfonates and carboxylates through a
municipal wastewater treatment plant for 10 d. The perfluoroalkyl
carboxylates were overall removed by the wastewater treatment process (25-40% removal). Perfluoroalkyl sulfonates were found to increase significantly
(~200%) in the final effluent, and the fluoroalkyl sulfonamide acetic acids were
found to increase by approximately 500% throughout the sludge process.
From this plant, significant quantities of fluorochemicals are discharged with
treated wastewater and biosolids, indicating that wastewater treatment plants are point sources of fluorinated alkyl substances and must be considered
when determining origins and behavior of fluorinated alkyl substances in the
environment. / Graduation date: 2005
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Microscopic evaluation of activated sludge from eleven wastewater treatment plants in Cape Town, South Africa / Pamela WelzWelz, Pamela Jean January 2008 (has links)
From June to November 2007, a microscopic analysis was conducted on the activated sludge from eleven selected wastewater treatment plants (WWTP's) belonging to the City of Cape Town. The primary objective was the identification of the dominant and secondary filamentous organisms. Other important criteria included were the floe character, diversity, filament index (Fl) and identification of the protozoan and metazoan communities. The operational data determined from routine analyses of the sludge, influent and effluent were used to assess the relationship of the filamentous population to wastewater characteristics and to compare this with previous findings. Fl values of >3 and dissolved sludge volume indices (DSVI's) of >150 were chosen as representing the possibility of bulking conditions being present. The five most prevalent dominant filaments were Type 0092, Type 1851, actinomycetes, Microthrix parvicella and Type 021N, being present in 74%, 31%, 22%, 17% and 14% of samples respectively. Type 0092 did not appear to be associated with bulking in any of the WWTP's, although it was often incidentally present as a co-dominant species when bulking conditions existed. All three WWTP's with the Modified Ludzack-Ettinger configuration harboured Type 1851 as the major dominant species, irrespective of whether the plants treated domestic or industrial effluent. Conditions suggestive of bulking were present in two of these WWTP's. Contrary to expectations, Type 1851 was often found as a dominant species where domestic waste was the primary influent. Type 021N and actinomycetes were strongly implicated when bulking occurred. The overgrowth of these filaments appeared to be related to factors such as nutrient deficiency (Type 021N) or the presence of large amounts of low molecular weight substances in the influent. Microthrix parvicella did not cause major bulking problems. There was a strong association between low levels of nitrates/nitrites in the clarifier supernatant and good phosphorous removal, irrespective of the configuration of the WWTP. The converse was also true. / Thesis ((M. Environmental Science))--North-West University, Potchefstroom Campus, 2009.
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Excess Sludge Reduction During Activated Sludge Municipal Wastewater Treatment by Integrating an Anoxic Holding Tank and Post-ultrasound Treatment to Enhance Biomass Maintenance MetabolismMarin-Hernandez, Juan 27 June 2012 (has links)
HT biomass sonicated at ES inputs < 56KJ/gTS decreased floc size by 41% and enhanced its metabolic activity by 50-250% compared to control. ES inputs >118 KJ/gTS caused HT biomass solubilization and irreversible loss of its metabolic activity and reflocculation ability. During continuous activated sludge processing (ASP) of real primary effluent the observed yield (Yobs) decreased by 20% compared to control ASP at SF (stress factor) of 1 (biomass exchanged without USPT). At SF of 0.5, 1 and 1.5 (biomass exchanged with USPT) the Yobs further decreased by 33, 25 and 44% respectively as compared to control. This indicated that combining biomass anoxic exposure with USPT enhanced sludge reduction by increasing microbial maintenance metabolism likely in combination with microbial flora shift in the ASP depending on SF.
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Characterization of Pretreatment Impacts on Properties of Waste Activated Sludge and DigestibilityKianmehr, Peiman January 2010 (has links)
Technologies for pretreatment of waste activated sludges (WAS) prior to digestion are of
increasing interest to wastewater treatment utilities because of their promise for improving
sludge digestibility and reducing the mass of biosolids remaining after digestion. While there
has been considerable study of pretreatment processes, a common approach to describing the
impact of pretreatments on sludge biodegradability has not been developed. The overall
objective of this study was to develop protocols that can be employed to characterize the impact
of pretreatment processes on WAS digestion.
Sonication and ozonation were employed as models of physical and chemical
pretreatment technologies respectively. A range of physical, chemical and biological responses
were evaluated to assess the impact of pretreatment on WAS properties as well as digestibility.
WAS samples that were generated over a range of solids residence times (SRTs) under
controlled operating conditions were employed to facilitate an assessment of the interaction
between pretreatment and WAS properties on digestibility.
The VS, COD and soluble TKN responses indicated that a significant fraction of the
WAS solids were solublized by sonication and ozonation, however, it appeared that the types of
materials which were solublized was affected by the SRT at which the WAS was generated and
the level of pretreatment. The results indicated that the impact of pretreatment on
biodegradability of WAS was not described by solublization values exclusively without
considering the SRT of the sludge and the level and type of pretreatment. A higher level of
proteinaceous materials was preferentially solublized as the result of pretreatment. Respirometry
revealed that both sonication and ozonation substantially reduced the viable heterotrophs in the
sludge and modestly increased the readily biodegradable fraction of COD. The ultimate yields of
CH4 and NH4 in BMP tests and VFAs in BAP tests revealed that pretreatment marginally
increased the ultimate digestibility of the sludges. Only a high dose of ozonation substantially
increased the digestibility of the 15 day SRT sludge. However, both sonication and ozonation
substantially increased the rate of hydrolysis which is typically the rate limiting process in WAS
digestion.
The BMP test was not a useful test to evaluate the rate of methane generation due to
inhibition of methanogens in the early days of BMP test for pretreated sludges. The comparison
between VFA and ammonia responses in day 10 of BAP test and ultimate values of these
responses after 60 days in BMP test revealed linear relationships between these responses.
According to these relationships, a set of models were introduced in this study. The models can
be employed to predict the ultimate methane and ammonia generation using soluble COD, VFA
or ammonia responses in day 10 of BAP tests. The BAP test was determined to be a shorter test
(10 days) than the BMP (55 to 60 days) test and could provide information on the rates of
hydrolysis and acidification/ammonification processes. Characterization of biodegradable and
non-biodegradable material in WAS samples was conducted using a simplified ADM1 model.
The characterization also revealed that proteins are a substantial fraction of biodegradable
materials. The estimated ammonia, VFA and methane values from the stoichiometric model
were similar to the corresponding values from the experiments. This supported the validity of the
simplified model for all sludges employed in this study.
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Undersökning av utökade användningsområden för Lotsbroverkets slam / Examination of expanded uses for the sewagesludge that is produced in LotsbroverketLindfors, Elin January 2012 (has links)
Lotsbroverket is the largest wastewater treatment plant on the Aland Islands and it isdesigned for handling wastewater from approximately 30 000 persons. In 2011,Lotsbroverket produced about 2800 m3 of dewatered sludge. The sewage sludge that isproduced is transported to a contractor where it is processed to eventually be used e.g.in the construction of green space. This study aims to investigate available applicationoptions in terms of the sewage sludge that is produced in Lotsbroverket. The main aimis to study the feasibility of using the produced sewage sludge as a fertilizer in theagriculture of the Aland Islands.The sludge already fulfills limit values for heavy metals in accordance with the Act"The Aland Government´s directive on the use of sewage sludge in agriculture." Inorder to clarify the sludge content of pharmaceutical and organic substances it isrequired that the substances are identified and a risk assessment is performed. In theliterature it is found that the risk of human exposure to these substances is low if thesludge is treated appropriately. Suggested appropriate treatment of the plant's sludge isthermophilic digestion whereby also pathogens are killed.The soil of the Aland Islands has a high content of phosphorus. Since 1995 there is anenvironmental program to which currently 95% of the island's farmers are connected.The program controls the use of fertilizers i.e. by setting maximum permitted levels ofphosphorus. Since sewage sludge contains relatively much phosphorus it may be alimitation of the use of sewage sludge on agricultural land of the Aland Island. That iswhy it would be suitable to use the sludge with a different fertilizer in order to obtainthe proper fertilizing properties.In Europe, the use of sewage sludge in agriculture is relatively widespread. Severalcountries have less strict laws regarding the sludge content than the Aland Islands.Because large amounts of fruits and vegetables annually are imported into the island,there is reason to believe that the population already consumes products grown onsludge treated soils. Several of the farmers on the Aland Islands are currently scepticalin terms of using sewage sludge in agriculture, mainly due to uncertainties in the sludgecontent. Regarding the certification of Lotsbroverket in accordance with the Swedishcertification system REVAQ no barriers have been found. To ensure that a certificationis possible, however, further investigations are required.
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Characterization of Pretreatment Impacts on Properties of Waste Activated Sludge and DigestibilityKianmehr, Peiman January 2010 (has links)
Technologies for pretreatment of waste activated sludges (WAS) prior to digestion are of
increasing interest to wastewater treatment utilities because of their promise for improving
sludge digestibility and reducing the mass of biosolids remaining after digestion. While there
has been considerable study of pretreatment processes, a common approach to describing the
impact of pretreatments on sludge biodegradability has not been developed. The overall
objective of this study was to develop protocols that can be employed to characterize the impact
of pretreatment processes on WAS digestion.
Sonication and ozonation were employed as models of physical and chemical
pretreatment technologies respectively. A range of physical, chemical and biological responses
were evaluated to assess the impact of pretreatment on WAS properties as well as digestibility.
WAS samples that were generated over a range of solids residence times (SRTs) under
controlled operating conditions were employed to facilitate an assessment of the interaction
between pretreatment and WAS properties on digestibility.
The VS, COD and soluble TKN responses indicated that a significant fraction of the
WAS solids were solublized by sonication and ozonation, however, it appeared that the types of
materials which were solublized was affected by the SRT at which the WAS was generated and
the level of pretreatment. The results indicated that the impact of pretreatment on
biodegradability of WAS was not described by solublization values exclusively without
considering the SRT of the sludge and the level and type of pretreatment. A higher level of
proteinaceous materials was preferentially solublized as the result of pretreatment. Respirometry
revealed that both sonication and ozonation substantially reduced the viable heterotrophs in the
sludge and modestly increased the readily biodegradable fraction of COD. The ultimate yields of
CH4 and NH4 in BMP tests and VFAs in BAP tests revealed that pretreatment marginally
increased the ultimate digestibility of the sludges. Only a high dose of ozonation substantially
increased the digestibility of the 15 day SRT sludge. However, both sonication and ozonation
substantially increased the rate of hydrolysis which is typically the rate limiting process in WAS
digestion.
The BMP test was not a useful test to evaluate the rate of methane generation due to
inhibition of methanogens in the early days of BMP test for pretreated sludges. The comparison
between VFA and ammonia responses in day 10 of BAP test and ultimate values of these
responses after 60 days in BMP test revealed linear relationships between these responses.
According to these relationships, a set of models were introduced in this study. The models can
be employed to predict the ultimate methane and ammonia generation using soluble COD, VFA
or ammonia responses in day 10 of BAP tests. The BAP test was determined to be a shorter test
(10 days) than the BMP (55 to 60 days) test and could provide information on the rates of
hydrolysis and acidification/ammonification processes. Characterization of biodegradable and
non-biodegradable material in WAS samples was conducted using a simplified ADM1 model.
The characterization also revealed that proteins are a substantial fraction of biodegradable
materials. The estimated ammonia, VFA and methane values from the stoichiometric model
were similar to the corresponding values from the experiments. This supported the validity of the
simplified model for all sludges employed in this study.
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Modeling Volatile Organic Sulfur Compounds In Anaerobic DigestionDu, Weiwei January 2010 (has links)
Anaerobic digestion is a common process for treatment of wastewater sludge from municipal sewage systems. Volatile sulfur compounds, including volatile organic sulfur compounds (VOSCs) and hydrogen sulfide, have been reported as the most odorous compounds in digestion emissions and impurities which can damage facilities for generation, transportation, storage, and utilization of biogas. There has been no comprehensive study on biological generation and degradation kinetics of VOSC or modeling VOSC behaviors through anaerobic sludge digestion. The goal of the present study was to establish a model for VOSC conversions in anaerobic sludge digestion which could facilitate quantitative analysis of VOSC emissions in anaerobic digestion.
VOSCs and methionine were employed in dosed batch tests. VOSC conversion processes in anaerobic methionine digestion have been identified. The kinetics for the identified VOSC degradation and conversion processes were determined at 35 and 55 °C respectively. Mixed-second order kinetics were found to best fit the conversion processes. A model was established based on the identified processes and estimated kinetic constants.
To extend the model to VOSC release in anaerobic sludge digestion, mesophilic and thermophilic incubations were conducted with four different sludge samples. The effects of temperature and sludge source on VOSC release patterns were assessed. It was found that an unidentified DMS generation mechanism was triggered in the mesophilic incubation of activated sludge in which iron was dosed.
To apply the model which was established based on methionine degradation in sludge digestion, hydrolysis of particulate materials was incorporated. The model simulations for VOSC behavior in thermophilic batch incubation were able to represent the observed VOSC releases. However, the simulations could not well fit the observed VOSC release at 35 ° because the model did not include the unidentified DMS generation mechanism.
Application of the model to bench-scale digesters was lack-of-fit. It may have been due to imprecise estimation of the degradable sulfur in the feed sludge. In addition, in the batch tests and digester operation the ratios of the raw and digested sludge were different. This might have resulted in different concentrations of the microorganisms which mediated biotransformations and hence resulted in different kinetic constants.
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