Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 93-98). Also available via the Internet.

Thesis (M.S. - Civil Engineering and Engineering Mechanics)--University of Arizona, 1986. / Includes bibliographical references (leaves 206-211).

Thesis (PhD (Chemical Engineering))--University of Pretoria, 2008. / Includes bibliographical references (p. 110-126)

The dewatering characteristics of polyaluminum chloride (Hyper⁺Ion 1050A) sludges were investigated using lab-scale tests including specific resistance to filtration (r*), capillary suction time (CST), and sludge pH. The effects of chemical conditioning (lime and cationic polymer) and mixing intensity (Gt) upon the sludge dewatering characteristics in a pilot-scale plate and frame press were also studied. The dewatering characteristics of the Hyper⁺Ion sludges were found to be dependent upon the influent water turbidity conditions; specifically, the ratio of aluminum coagulant to total dry solids in the sludge. Lime was an effective conditioner for doses that produced a sludge pH value in the range of 11.5 to 11.8 which, again, was a direct function of the aluminum coagulant fraction in the sludge. Cationic polymer and a combination of lime and polymer were also effective conditioning schemes when the appropriate dose and mixing intensity were applied. / Master of Science

<p>Sedan december 2003 har Kalmar läns slakteris (KLS) nya reningsverk varit i drift. Entreprenör för det nya reningsverket samt driftansvariga under det två första åren är Läckeby Water Group. Verket är av SBR-typ (Sekventiell Biologisk Rening) med biologisk kväverening och kemisk fällning av fosfor med hjälp av järnklorid. Från slakteriet leds avloppsvattnet genom en 2 km lång ledning ner till reningsanläggningen. Verket hade under 2004 problem med höga halter fosfor i utgående vatten, flertalet mekaniska haverier samt två perioder av slamsvällning. Slamsvällningen orsakades av filamentösa (trådformiga) bakterier, första gången av Thiothrix spp. och andra gången av Typ 021N. Syftet med examensarbetet var att finna orsaken till den senare slamsvällningen samt att söka förebyggande åtgärder mot Typ 021N. Examensarbetet utfördes genom litteraturstudier, laboratorieförsök, fullskaleförsök, genomgång av driftsdata samt mikroskopering av aktivt slam vid verket.</p><p>Utifrån litteraturstudier konstaterades att filamentösa bakterier kan gynnas under perioder av låga syrehalter samt av låg näringstillförsel eftersom dessa bakterier har en högre tillväxthastighet vid låga substratkoncentrationer än flockbildande bakterier. Specifikt för Typ 021N är att dessa har möjlighet att utnyttja reducerat svavel som energikälla samt gynnas vid tillgång på korta lättnedbrytbara kolföreningar. Laboratorieförsök visade inte entydigt att låga fosfor eller syrehalter gynnade de filamentösa bakterierna. Inverkan av FeCl3, Ecofloc, PAXXL60, NaOCl och H2O2 studerades under korttids laboratorieförsök och effekten utvärderades i mikroskop. I några fall hämmades filamenten men aldrig utan att även påverka övriga mikroorganismer negativt. PAX-XL60 hämmade filamentförkomsten mest och påverkade andra organismer förhållandevis lite. Tillsats av PAX i filamenthämmande och flockbildande syfte utfördes därefter i fullskala. Effekten av tidigare tillsatser av NaOCl och H2O2 i filamenthämmande syfte studerades och visade sig ha givit varierande resultat. NaOCl visade sig effektivt bekämpa filamentösa bakterier i processen då inblandning skedde under rätt förutsättningar.</p><p>Processdata för våren 2004 jämfördes med data från en period under hösten, vilken följdes av en slamsvällning. Perioderna visade stora skillnader m.a.p. syrehalt, temperatur, dosering av järnklorid och organisk belastning. En on-line mätning i inkommande vatten visade på mycket höga halter av svavelväte. Svavelväte bildas under anaeroba förhållanden t.ex. i stillastående avloppsvatten. Orsaker till slamsvällningen i september-oktober 2004 tros vara höga halter av svavelväte, perioder med låga syrehalter, höga vattentemperaturer samt tillgång på lättnedbrytbart organiskt material. Svavelvätet kan förslagsvis elimineras genom en tidsstyrd dosering av CaNO3 i inkommande ledning. Noggrann övervakning av syre samt tillgång på syre måste garanteras i processen. Det inkommande vattnets mikroflora kan förändras genom installation av en aerob selektor för att gynna de flockformande bakterierna. För att sänka fosforhalterna i utgående vatten samt att inte riskera fosforbrist i processen har en tillfällig efterfällning med extra tillsats av FeCl3 och polymer installerats.</p> / <p>In December 2003 the new plant treating slaughterhouse wastewater from KLS was taken into operation. Läckeby Water Group was entrepreneur and responsible for the maintenance during the following two years. The treatment plant is of SBR-type and has biological nitrate removal and chemical precipitation of phosphate with iron chloride. The wastewater from the slaughterhouse passes a 2 km long pipeline before entering the treatment plant. During 2004, the plant had problems with high levels of phosphorous in the effluent, several mechanical problems and two occasions of sludge bulking caused by filamentous bacteria. The first incident was caused by Thiothrix spp. and the second by Type 021N. The aim with the thesis was to find causes for the latest period of sludge bulking as well as investigate preparatory actions against Type 021N. The thesis included literature studies, laboratory and full-scale tests, evaluation of prior process data and continuous microscopic analysis of the activated sludge at the plant.</p><p>The literature study showed that filamentous bacteria are favoured by low oxygen and low nutrient concentrations due to their possibly higher growth rate during low substrate concentrations. Type 021N, specifically, can use reduced sulphides as energy source and benefits from an excess of low molecular substrates. Laboratory experiments did not verify that the filamentous bacteria were favoured by low oxygen concentration or low phosphate levels. The effect of FeCl3, Ecofloc, PAX-XL60, NaOCl and H2O2 added to a bulking sludge was evaluated by microscopic analysis. No chemical was found to suppress the filamentous bacteria without also affecting the floc-forming bacteria negatively. PAX-XL60 showed the largest negative effects on filamentous bacteria and only a minor impact on other microorganisms. Full-scale tests with PAX were thereafter performed in order to suppress filamentous bacteria as well as flocculate particulate solids. The effect of earlier additions of NaOCl and H2O2 into the process gave varied results. NaOCl was efficient against filamentous bacteria when addition was made during correct circumstances.</p><p>Process data from two separate periods during 2004 was compared. One period was followed by good effluent values and another period by a sludge bulking period. Large differences between the two periods were seen in oxygen conditions, temperature, FeCl3 dosage and organic load. Measurements on influent wastewater showed high levels of hydrogen sulphide, which can be produced during anaerobe conditions i.e. in stagnant sewage pipes. Likely causes for the sludge bulking in September-October 2004 were high levels of hydrogen sulphide in the influent, periods of insufficient oxygen concentrations, high water temperatures and access to easy degradable substrate. The hydrogen sulphide can be eliminated through time-controlled dosage of CaNO3 in influent pipeline. Sufficient oxygen levels must be guaranteed in the process. The microbiological fauna in influent can be changed by installation of an aerobe selector to benefit floc-forming bacteria. To lower the phosphorous levels in effluent water and not risk phosphorous deficiency in the process a post-precipitation have been installed. The post-precipitation include extra dosage of FeCl3 and polymer and a drum screen to minimize suspended solids.</p>

A number of advanced pre-treatment techniques and methods have been evaluated for the sole purpose of improving digestibility of waste activated sludge. The pre-treatment of waste activated sludge (WAS) offers the benefit of releasing solubilized substrates, making them readily available to be utilized in the anaerobic digestion process. Other potential benefits include: reducing shock loading to the digester, improving overall digestibility and potentially providing filament / foaming control. Chlorine dioxide, a well-known disinfectant and oxidizing agent has been utilized in many drinking water processes around the world. Its use in wastewater treatment processes however is limited; especially in Canada where legislation has prevented its use for final effluent disinfection. As an oxidizing agent, chlorine dioxide induces cell rupture resulting in the release of soluble material, which when fed into the digester, may serve as readily available substrate for active microorganisms. This mode of action creates the potential for chlorine dioxide to be used as a sludge pre-treatment agent to improve digester performance and in alleviating pre-existing filamentous sludge bulking. This study was conducted using waste activated sludge obtained from the City of Winnipeg’s South End Water Pollution Control Centre (SEWPCC), with the following objectives: 1. Determine the efficacy of chlorine dioxide in alleviating pre-existing filamentous sludge bulking; 2. Determine chlorine dioxide ability to increase WAS solubilization; and 3. Define impact of chlorine dioxide on anaerobic digester performance. WAS pre-treatment using chlorine dioxide was found to be effective in alleviating filamentous bulking. This is significant as filamentous bulking in the activated sludge may lead several problems downstream. Following pre-treatment, sludge bulking was determined to be alleviated as observed by photomicrographic evidence and as measured by a 57% decrease in the stirred sludge volume index (sSVI). Particulate COD solubilization increased by 60%, 76%, and 74% over the untreated sludge for WAS pre-treated with 25, 50, and 100 mg ClO2/L (v/v), respectively. The pre-treatment of sludge using chlorine dioxide did not have any negative impact on digester performance although it also did not lead to improved performance. The volatile solids destruction and COD removal remained unchanged for both untreated and pre-treated sludge. Chlorine dioxide pre-treatment did not affect anaerobic digestion even at the lowest SRT evaluated; it is possible to decrease the digester SRT to as low as 6 days while maintaining the solids destruction and COD removal capability. Biogas production did not improve with increasing chlorine dioxide dosage during pre-treatment but also was not hindered by the pre-treatment agent. Chlorine dioxide was shown to alleviate filamentous bulking and improve solubility and has the potential to improve digester performance without negative impacts to the digester. However, the full benefit of the pre-treatment method may only be realized for complex “difficult to disintegrate” sludge types. / October 2016

Sedan december 2003 har Kalmar läns slakteris (KLS) nya reningsverk varit i drift. Entreprenör för det nya reningsverket samt driftansvariga under det två första åren är Läckeby Water Group. Verket är av SBR-typ (Sekventiell Biologisk Rening) med biologisk kväverening och kemisk fällning av fosfor med hjälp av järnklorid. Från slakteriet leds avloppsvattnet genom en 2 km lång ledning ner till reningsanläggningen. Verket hade under 2004 problem med höga halter fosfor i utgående vatten, flertalet mekaniska haverier samt två perioder av slamsvällning. Slamsvällningen orsakades av filamentösa (trådformiga) bakterier, första gången av Thiothrix spp. och andra gången av Typ 021N. Syftet med examensarbetet var att finna orsaken till den senare slamsvällningen samt att söka förebyggande åtgärder mot Typ 021N. Examensarbetet utfördes genom litteraturstudier, laboratorieförsök, fullskaleförsök, genomgång av driftsdata samt mikroskopering av aktivt slam vid verket. Utifrån litteraturstudier konstaterades att filamentösa bakterier kan gynnas under perioder av låga syrehalter samt av låg näringstillförsel eftersom dessa bakterier har en högre tillväxthastighet vid låga substratkoncentrationer än flockbildande bakterier. Specifikt för Typ 021N är att dessa har möjlighet att utnyttja reducerat svavel som energikälla samt gynnas vid tillgång på korta lättnedbrytbara kolföreningar. Laboratorieförsök visade inte entydigt att låga fosfor eller syrehalter gynnade de filamentösa bakterierna. Inverkan av FeCl3, Ecofloc, PAXXL60, NaOCl och H2O2 studerades under korttids laboratorieförsök och effekten utvärderades i mikroskop. I några fall hämmades filamenten men aldrig utan att även påverka övriga mikroorganismer negativt. PAX-XL60 hämmade filamentförkomsten mest och påverkade andra organismer förhållandevis lite. Tillsats av PAX i filamenthämmande och flockbildande syfte utfördes därefter i fullskala. Effekten av tidigare tillsatser av NaOCl och H2O2 i filamenthämmande syfte studerades och visade sig ha givit varierande resultat. NaOCl visade sig effektivt bekämpa filamentösa bakterier i processen då inblandning skedde under rätt förutsättningar. Processdata för våren 2004 jämfördes med data från en period under hösten, vilken följdes av en slamsvällning. Perioderna visade stora skillnader m.a.p. syrehalt, temperatur, dosering av järnklorid och organisk belastning. En on-line mätning i inkommande vatten visade på mycket höga halter av svavelväte. Svavelväte bildas under anaeroba förhållanden t.ex. i stillastående avloppsvatten. Orsaker till slamsvällningen i september-oktober 2004 tros vara höga halter av svavelväte, perioder med låga syrehalter, höga vattentemperaturer samt tillgång på lättnedbrytbart organiskt material. Svavelvätet kan förslagsvis elimineras genom en tidsstyrd dosering av CaNO3 i inkommande ledning. Noggrann övervakning av syre samt tillgång på syre måste garanteras i processen. Det inkommande vattnets mikroflora kan förändras genom installation av en aerob selektor för att gynna de flockformande bakterierna. För att sänka fosforhalterna i utgående vatten samt att inte riskera fosforbrist i processen har en tillfällig efterfällning med extra tillsats av FeCl3 och polymer installerats. / In December 2003 the new plant treating slaughterhouse wastewater from KLS was taken into operation. Läckeby Water Group was entrepreneur and responsible for the maintenance during the following two years. The treatment plant is of SBR-type and has biological nitrate removal and chemical precipitation of phosphate with iron chloride. The wastewater from the slaughterhouse passes a 2 km long pipeline before entering the treatment plant. During 2004, the plant had problems with high levels of phosphorous in the effluent, several mechanical problems and two occasions of sludge bulking caused by filamentous bacteria. The first incident was caused by Thiothrix spp. and the second by Type 021N. The aim with the thesis was to find causes for the latest period of sludge bulking as well as investigate preparatory actions against Type 021N. The thesis included literature studies, laboratory and full-scale tests, evaluation of prior process data and continuous microscopic analysis of the activated sludge at the plant. The literature study showed that filamentous bacteria are favoured by low oxygen and low nutrient concentrations due to their possibly higher growth rate during low substrate concentrations. Type 021N, specifically, can use reduced sulphides as energy source and benefits from an excess of low molecular substrates. Laboratory experiments did not verify that the filamentous bacteria were favoured by low oxygen concentration or low phosphate levels. The effect of FeCl3, Ecofloc, PAX-XL60, NaOCl and H2O2 added to a bulking sludge was evaluated by microscopic analysis. No chemical was found to suppress the filamentous bacteria without also affecting the floc-forming bacteria negatively. PAX-XL60 showed the largest negative effects on filamentous bacteria and only a minor impact on other microorganisms. Full-scale tests with PAX were thereafter performed in order to suppress filamentous bacteria as well as flocculate particulate solids. The effect of earlier additions of NaOCl and H2O2 into the process gave varied results. NaOCl was efficient against filamentous bacteria when addition was made during correct circumstances. Process data from two separate periods during 2004 was compared. One period was followed by good effluent values and another period by a sludge bulking period. Large differences between the two periods were seen in oxygen conditions, temperature, FeCl3 dosage and organic load. Measurements on influent wastewater showed high levels of hydrogen sulphide, which can be produced during anaerobe conditions i.e. in stagnant sewage pipes. Likely causes for the sludge bulking in September-October 2004 were high levels of hydrogen sulphide in the influent, periods of insufficient oxygen concentrations, high water temperatures and access to easy degradable substrate. The hydrogen sulphide can be eliminated through time-controlled dosage of CaNO3 in influent pipeline. Sufficient oxygen levels must be guaranteed in the process. The microbiological fauna in influent can be changed by installation of an aerobe selector to benefit floc-forming bacteria. To lower the phosphorous levels in effluent water and not risk phosphorous deficiency in the process a post-precipitation have been installed. The post-precipitation include extra dosage of FeCl3 and polymer and a drum screen to minimize suspended solids.

Nutrients and cations have significant effect on activated sludge characteristics and therefore effect the efficiency of whole processes. To determine the properties in phosphorus deficient medium and the effect of calcium ions two reactor sets with two different phosphorus concentration (C/N/P=100/5/0.05 and C/N/P=100/5/1), three different concentrations of calcium (0.5, 5, 15 meq/L) were operated with 8 days of sludge residence time and an effective volume of 2 L. Results showed amount and composition of EPS was dependent on calcium and phosphorus concentrations. Except for the highest calcium concentration, increase in phosphorus concentration resulted in increase in total EPS production. Under phosphorus deficient conditions, calcium ions stimulated the production of carbohydrate type polymers and viscous bulking was observed. However, the increase in phosphorus concentration led to increase in protein type polymer production and bulking condition was cured. Addition of calcium ions increased conductivity in both cases, but increase in phosphorus concentration caused decrease in conductivity. Increase in phosphorus concentration had improved settleability, dewaterability and rheology of sludge. Moreover, effluent turbidity was decreased and COD removal efficiency was recorded as greater than 95 % for all calcium concentrations under phosphorus sufficient conditions. Microscopic analyses showed that under phosphorus deficient conditions flocs were weak, dispersed and nonresistant. Increase in phosphorus concentration resulted in improvement of floc structure. Same Enterobacter and Citrobacter species were identified at all calcium concentrations under phosphorus deficient conditions. Yet, under phosphorus sufficient conditions different species were identified in control reactor as compared to 5 meq/L and 15 meq/L concentrations.

The activated sludge process comprises a complex and enriched culture of a mixture of generalist and specialist organisms. The lack of knowledge on species diversity of microbial communities is due to the simplicity of bacterial morphology and the phenotypic characters, and the unculturable portion of microbial cells in natural habitats. Although a wide range of bacteria can be isolated using conventional microbiological techniques of sample dilution and spread plate inoculation, many well-known activated sludge bacteria can not be isolated using them. The individual microbial cells in activated sludge grow in aggregates that consist of floc-forming organisms together with filamentous microorganisms that form the backbone of the activated sludge floes. Overgrowth of these filamentous microorganisms often causes settling problems called bulking and foaming. These problems consist of slow settling, poor compaction of solids and foam overflow into the effluent. Although methods for the isolation of filamentous bacteria from mixed liquor samples have been investigated, the attempts have been largely unsuccessful. In this study we investigated bulking and foaming activated sludge to identify the dominant filamentous organisms using microscopy and molecular techniques. Using microscopy, the dominant filament associated with the foaming sample was "Microthrix parvicella" and in the bulking sample was Nocardia spp. The foaming sample was investigated using molecular techniques that involved 165 rDNA sequencing. Although some of the clones isolated from the sludge foam were associated with filamentous bacteria causing foam, no positive identification could be made. In the part of the study that was conducted in Australia, a rRNA-targeted oligonucleotide probe was designed for the identification of a filamentous organism occurring in activated sludge foam. This organism resembled Eikelboom Type 0041 and was classified in the candidate bacterial division TM7. The discrepancy that the sequence data did not indicate the dominant filamentous organisms observed by microscopy, highlights the fact that natural microbial communities need to be studied using a combination of techniques since none of the techniques available are sufficient to determine the complete community structure of complex communities such as activated sludge. / Dissertation (MSc (Microbiology))--University of Pretoria, 2005. / Microbiology and Plant Pathology / unrestricted

Submitted in fulfilment of the requirements of the degree of Master of Technology: Biotechnology, Durban University of Technology, Durban, South Africa, 2014. / Wastewater treatment plants (WWTPs) frequently experience bulking and foaming episodes, which present operational challenges by affecting sludge settling due to the excessive proliferation of filamentous bacteria. Various control strategies have been implemented over the years to minimize filamentous growth, however, filamentous bulking still remains an unresolved problem in many WWTPs worldwide. The current study focused on developing and optimizing remedial measures viz., specific and non-specific methods to reduce problematic filamentous bacteria in a full-scale WWTP. Specific methods demonstrated the influence of plant operational parameters viz. chemical oxygen demand, influent N-NH4+, food to microorganism ratio, dissolved oxygen, temperature and pH on the abundance of filamentous bacteria. A cumulative logit model was used to determine the significant relationships between the individual filamentous bacteria at present and the prevailing plant operational parameters. Using the above statistical approach, significant observations and predictions were made with respect to the individual filamentous growth under certain operational parameters. With further validation, this model could be successfully applied to other full-scale WWTPs identifying specific parameters that could contribute to filamentous bulking, thus providing a useful guide for regulating specific filamentous growth. Non-specific control methods such as chlorine, ultraviolet irradiation and ozone treatment were investigated on filamentous bacteria using a live/dead staining technique. To achieve at least 50% reduction of filamentous bacteria, a chlorine dose of 10 mg Cl2/L was required, all filaments were killed at a dose of 22 mg Cl2/L. In addition, an effective UV and ozone dose of 4418.91 μw seconds/cm2 and ±20 mg O3/L respectively, was required to kill 50% of the filamentous bacterial population. Among the three non-specific methods, ozone treatment seemed to be an effective method in controlling the filamentous population with a low negative impact to the surrounding environment. This study serves as a useful guide on the problems and control of filamentous bulking in activated sludge plants. / M