Floc density measurements may play a significant role in analyzing sludge dewatering characteristics. A laboratory technique was developed to measure this property by means of isopycnic centrifugation. Four laboratory sludges were subjected to a series of dewatering tests: gravity thickening, centrifugation, vacuum filtration, and high-pressure dewatering. Each sludge was analyzed for changing macro- and micro-properties during increasing stages of dewatering. It was concluded that sludge thickening rates are influenced by aggregate volume fractions, sludge density, suspension porosity, and the total surface area occupied by sludge aggregates. The extent of mechanical dewatering is impacted by similar parameters; namely, floc volume fractions, sludge density, cake porosity, and the total surface area occupied by sludge floc. By interpreting the laboratory data, a model was formulated to describe changes in water distribution during the dewatering of sludges. This model includes a speculative view of the qualification and quantification of water-types. / Master of Science

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

<p>Hedesunda reningsverk är beläget i södra delen av Gävle kommun och hanterar avloppsvatten från Hedesunda samhälle och ett fåtal närbelägna byar. Antalet anslutna personer är strax över 1500. Reningsverket byggdes på 1960-talet och byggdes om i slutet av 1990-talet. Vid ombyggnaden anlades torkbäddar för avvattning av det slam som produceras vid reningsverket. Inledningsvis fungerade dessa torkbäddar bra men sedan 2005 har slammet i bäddarna inte avvattnats i önskad omfattning.</p><p> </p><p>Syftet med detta examensarbete var att utreda hur slamavvattningen i Hedesunda ska se ut i framtiden. Utgångspunkten var att den nuvarande lösningen är otillräcklig och att en förändring är nödvändig. Inledningsvis delades frågeställningen upp i två separata delar: avvattning av slammet och avsättning för avvattnat slam. Fokus låg på ekonomiska och miljömässiga aspekter av slamhantering och en sammanvägning av dessa gjordes där så var möjligt.</p><p> </p><p>Frågan om hur avvattningen bör se ut undersöktes genom att en enkät skickades ut till nio olika företag som levererar avvattningsutrustning. Dessa fick svara på 17 frågor om vilken lösning de ansåg vara bäst lämpad för reningsverket i Hedesunda. Sammanlagt samlades sex olika svar in. Utöver dessa undersöktes även alternativet att restaurera de befintliga torkbäddarna närmare. Detta skedde bland annat genom provtagning och analys av slammet i bäddarna. De olika alternativen för slamavvattning sammanställdes och jämfördes genom att varje undersökt parameter delades in i intervall som gav olika betyg. De tre alternativ som enligt denna undersökning ansågs bäst lämpade var att restaurera de befintliga bäddarna, att anlägga vassbäddar eller att installera en mindre silbandpress.</p><p> </p><p>Då slammet avvattnats återstår frågan kring hur det avvattnade slammet ska hanteras. Detta undersöktes genom att två alternativ studerades närmare. Dessa var att fortsätta med den nuvarande hanteringen som är kompostering och tillverkning av anläggningsjord eller att certifiera slammet genom REVAQ och sprida det på åkermark. Ett försök till att skatta kostnaden för de båda alternativen gjordes, bland annat genom att frågor ställdes till de kommuner/driftbolag som idag är certifierade enligt REVAQ. Kostnaden för certifiering och spridning på jordbruksmark är betydligt mycket högre än kostnaden för kompostering. Certifieringsalternativet innebär dock en större måluppfyllelse i och med att fosfor återförs till produktiv mark.   </p><p> </p><p>Resultatet av studien är ett konkret förslag på hur slamavvattning och avsättning för slam vid Hedesunda reningsverk kan skötas i framtiden. Detta förslag innebär att de nuvarande torkbäddarna restaureras och att möjligheterna att certifiera flera delar av Gästrike Vatten AB:s verksamhet utreds närmare. Att enbart certifiera slam från Hedesunda reningsverk anses ekonomiskt orimligt.</p> / <p>Hedesunda wastewater treatment plant (wwtp) is located in the southern part of Gävle municipality in Sweden. The wwtp treats wastewater from Hedesunda community and a few nearby villages. All in all there are approximately 1500 persons connected to the plant. Hedesunda wwtp was originally built in the 1960’s and was restored in the late 1990’s. At the restoration sludge drying beds were built on the site for sludge dewatering. Initially, these beds worked fine but since 2005 the dewatering result has not been satisfactory.</p><p> </p><p>The objective of this master thesis has been to investigate different alternatives for a more effective sludge handling at Hedesunda wwtp in the future. Initially the sludge handling process was divided into two different parts: sludge dewatering and management of dewatered sludge. The focus has been on economical and environmental aspects of sludge handling and where it’s been possible these factors have been weight together.</p><p> </p><p>The question of how a more effective dewatering of sludge could be achieved was answered by a questionnaire that was sent to different companies that supply dewatering equipment to the Swedish market. Altogether six answers were collected. Besides these answers the option of restoring the existing sludge drying beds was also considered. The latter was done by sampling and analyzing sludge in the existing beds, among other things. The different options for dewatering were compiled and compared in a matrix where every parameter was split up in intervals and assigned grades. Three options that received the highest total grade were considered the best options. These were: restoring the sludge drying beds, reed beds and a small belt filter press.</p><p> </p><p>The matter of how to handle the dewatered sludge was simplified to a study of only two alternatives. These were to continue the present handling or to certify the sludge according to REVAQ and use it as fertilizer. Attempts to estimate the cost for the two alternatives were made. The cost for certification is higher than the cost for composting, but to certify the sludge will lead to a higher target achievement.</p><p> </p><p>The study resulted in concrete suggestions for how the sludge at Hedesunda wwtp can be handled in the future. This suggestion states that the existing sludge drying beds should be restored and that the possibility to certify several wwtp:s within Gästrike Vatten AB should be investigated. It is not considered economically plausible to certify sludge from Hedesunda wwtp alone.</p>

Hedesunda reningsverk är beläget i södra delen av Gävle kommun och hanterar avloppsvatten från Hedesunda samhälle och ett fåtal närbelägna byar. Antalet anslutna personer är strax över 1500. Reningsverket byggdes på 1960-talet och byggdes om i slutet av 1990-talet. Vid ombyggnaden anlades torkbäddar för avvattning av det slam som produceras vid reningsverket. Inledningsvis fungerade dessa torkbäddar bra men sedan 2005 har slammet i bäddarna inte avvattnats i önskad omfattning.   Syftet med detta examensarbete var att utreda hur slamavvattningen i Hedesunda ska se ut i framtiden. Utgångspunkten var att den nuvarande lösningen är otillräcklig och att en förändring är nödvändig. Inledningsvis delades frågeställningen upp i två separata delar: avvattning av slammet och avsättning för avvattnat slam. Fokus låg på ekonomiska och miljömässiga aspekter av slamhantering och en sammanvägning av dessa gjordes där så var möjligt.   Frågan om hur avvattningen bör se ut undersöktes genom att en enkät skickades ut till nio olika företag som levererar avvattningsutrustning. Dessa fick svara på 17 frågor om vilken lösning de ansåg vara bäst lämpad för reningsverket i Hedesunda. Sammanlagt samlades sex olika svar in. Utöver dessa undersöktes även alternativet att restaurera de befintliga torkbäddarna närmare. Detta skedde bland annat genom provtagning och analys av slammet i bäddarna. De olika alternativen för slamavvattning sammanställdes och jämfördes genom att varje undersökt parameter delades in i intervall som gav olika betyg. De tre alternativ som enligt denna undersökning ansågs bäst lämpade var att restaurera de befintliga bäddarna, att anlägga vassbäddar eller att installera en mindre silbandpress.   Då slammet avvattnats återstår frågan kring hur det avvattnade slammet ska hanteras. Detta undersöktes genom att två alternativ studerades närmare. Dessa var att fortsätta med den nuvarande hanteringen som är kompostering och tillverkning av anläggningsjord eller att certifiera slammet genom REVAQ och sprida det på åkermark. Ett försök till att skatta kostnaden för de båda alternativen gjordes, bland annat genom att frågor ställdes till de kommuner/driftbolag som idag är certifierade enligt REVAQ. Kostnaden för certifiering och spridning på jordbruksmark är betydligt mycket högre än kostnaden för kompostering. Certifieringsalternativet innebär dock en större måluppfyllelse i och med att fosfor återförs till produktiv mark.      Resultatet av studien är ett konkret förslag på hur slamavvattning och avsättning för slam vid Hedesunda reningsverk kan skötas i framtiden. Detta förslag innebär att de nuvarande torkbäddarna restaureras och att möjligheterna att certifiera flera delar av Gästrike Vatten AB:s verksamhet utreds närmare. Att enbart certifiera slam från Hedesunda reningsverk anses ekonomiskt orimligt. / Hedesunda wastewater treatment plant (wwtp) is located in the southern part of Gävle municipality in Sweden. The wwtp treats wastewater from Hedesunda community and a few nearby villages. All in all there are approximately 1500 persons connected to the plant. Hedesunda wwtp was originally built in the 1960’s and was restored in the late 1990’s. At the restoration sludge drying beds were built on the site for sludge dewatering. Initially, these beds worked fine but since 2005 the dewatering result has not been satisfactory.   The objective of this master thesis has been to investigate different alternatives for a more effective sludge handling at Hedesunda wwtp in the future. Initially the sludge handling process was divided into two different parts: sludge dewatering and management of dewatered sludge. The focus has been on economical and environmental aspects of sludge handling and where it’s been possible these factors have been weight together.   The question of how a more effective dewatering of sludge could be achieved was answered by a questionnaire that was sent to different companies that supply dewatering equipment to the Swedish market. Altogether six answers were collected. Besides these answers the option of restoring the existing sludge drying beds was also considered. The latter was done by sampling and analyzing sludge in the existing beds, among other things. The different options for dewatering were compiled and compared in a matrix where every parameter was split up in intervals and assigned grades. Three options that received the highest total grade were considered the best options. These were: restoring the sludge drying beds, reed beds and a small belt filter press.   The matter of how to handle the dewatered sludge was simplified to a study of only two alternatives. These were to continue the present handling or to certify the sludge according to REVAQ and use it as fertilizer. Attempts to estimate the cost for the two alternatives were made. The cost for certification is higher than the cost for composting, but to certify the sludge will lead to a higher target achievement.   The study resulted in concrete suggestions for how the sludge at Hedesunda wwtp can be handled in the future. This suggestion states that the existing sludge drying beds should be restored and that the possibility to certify several wwtp:s within Gästrike Vatten AB should be investigated. It is not considered economically plausible to certify sludge from Hedesunda wwtp alone.

The master’s thesis is focused on the issue of solar drying of sewage sludge. The sludge management of wastewater treatment plants is described in the first part of this thesis. This theoretical part also deals with description of drying and dryers used for sludge treatment. The second part of the thesis is focused on the experimental solar drying of sewage sludge and the evaluation of the results.

The purpose of this study was to determine how chemical conditioning agents and mechanical dewatering devices affect sludge dewatering with respect to shear. Bench scale experiments were performed to determine the effect of shear and mole charge on polymer dose requirements using anaerobically digested sludge. Lime, ferric chloride, and polymer were used to condition anaerobically digested sludge to evaluate the influence of these conditioning agents, separately and in combination, on shear resistance. Dewatering studies were performed using a plate and frame press, a centrifuge, and a screw press to determine the amount of shear within each device and to develop a means of estimating polymer dose for each device. It was determined that increased molecular charge of polymer decreased chemical dose requirements and improved shear resistance. Both lime and ferric chloride improved sludge dewatering rates but only ferric chloride conditioned against shear. Ferric chloride addition prior to polymer conditioning improved sludge shear resistance, improved the dewatering rate (CST), and decreased the required polymer dose. The dewatering study using the plate and frame press verified that polymer dose could be estimated using CST values and a Gt value of approximately 30,000. Also, ferric chloride in combination with polymer improved filtrate quality, increased the cake solids concentration, and increased the filtrate volume throughput of sludge conditioned with lower polymer doses than if polymer alone was used. The dewatering study using a high speed centrifuge found that polymer dose could be estimated using CST values at a Gt between 10,000 and 20,000 or by use of the wedge zone simulator. The dewatering study of the screw press found that CST values and the wedge zone simulator under predicted polymer dose. This was thought to be the result of shear in the feed system prior to dewatering. / Master of Science

The first part of this diploma thesis targets in the formation of summary of methods of sewage sludge thermal treatment. Sludge is dangerous material rising from water treatment. Original water pollution is concentrated in sludge. Spectrum of the different methods of sludge disposal is very vast, thermal methods belong to the most advanced ones. Nowadays, legislative rules and regulations make more restrictive, hence sludge disposal is problematic because of economic and ecological view of point. The second part of this diploma thesis is dealt with perspective sludge management at the Central Waste Water Treatment Plant Prague concerning sludge drying and consequent sludge incineration.

The thesis is focused on the sludge management at root sewage treatment plants with focus on volum eis highest – sludge manahement. Sludge dewatering using sludge dryiing bed is still condemned designers mainly due to their lack of experience, while at the same time enforcing technologically complex solutions. Therefore, the thesis focuses on the break down balance hydrological equation sludge drying bed, which includes all parameters affecting water balance system. The result is a proposal not only design, but in particular a description of input data and the governing equations in software Reed-Bed, which is calibrated own operational results obtainde for the two sewage treatment plants (village Dražovice and Kotenčice). Reed-Bed software will perform sevetal functions: setting the ground area of sludge bed, investment costs required for the implementation of sludge bed, return on investment, the determination of moisture contene of sludge in the sludge bed and maximum lenght of the dewatering period with regard to wetland vegetation. The second largest item within sludge system creates biomass wetland plants, so work deals with possibilities biomass processing plant at the end of the growing season. Technological processing of biomass was tested on common reed, final product pellets for heating.

Pursuing the possibilities of increasing efficiency, saving costs and improving environmental performance more and more companies today are looking into the possibilities of industrial synergies between companies andprocesses. This study is considering the possibilities of industrial symbiosis between combined heat and power plant (Fortum) and a waste sorting facility (Ragn Sells). The paper shows possible scenarios of utilization heat fromCHP for the various processes within the waste treatment facility. The work includes the overview of previous research done in this area as well as theoretical analysisand estimation of the probable economic and environmental effects from the application of industrial symbiosis. The study covers several possibilities for the industrial symbiosis between CHP and waste treatment facility in form of heat application for the waste streams upgrading.The study proposes the heat application for the following processes: composting speed-up, anaerobic digestion, sludge drying, waste oil treatment and concrete upgrading. In the result of the work the conclusions are made concerning the possibility and feasibility of application of the proposed scenarios and their environmentaland economic effects. / Division Industrial Ecologywww.kth.se/itm/indecowww.ima.kth.se