Sludge accumulation, treatment and disposal can represent a high percentage of the operating cost for a wastewater system. This is especially important for small-scale and onsite wastewater treatment systems, where sludge removal can be one of the few operating costs of the system. In 2000, as a result of a large number of septic system failures, the community of Wardsville installed a Clearford Industries Inc. Small Bore Sewer™ (SBS™) system which included two-chamber 3600 L tanks located on the properties of individual homes. The tanks were collectively attached to a small bore piping system to deliver the effluent from the tanks to a small community wastewater treatment system. During the summer of 2007, a field study was initiated with a community survey, followed by a review of candidate sites, leading to the selection of 29 sites for site investigation and sampling. Sampling involved the collection of samples for sludge characterization along with the measurements of the height of solids (scum and sludge) within the tank. The data were analyzed to determine the factors having a statistically significant impact on solids accumulation rates within each of the two chambers of the tank. Household water usage was found to be the variable having the strongest association with sludge and scum accumulation, and models were estimated relating solids accumulation to water usage in order predict pump out frequency. A second field sampling program was conducted in Wardsville during April 2008, involving only the first chamber of 13 primary clarifier tanks. Overall contributions have been made in understanding and quantifying solids accumulation rates and sludge characterization in onsite primary clarifier tanks. As well, the information gained from the analysis of the data collected provides a meaningful insight into the factors influencing solids accumulation within individual residential primary clarifier tanks, and points to future research directions for understanding the factors influencing solids accumulation. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-04-25 15:34:46.243

Sludge accumulation, treatment and disposal can represent a high percentage of the operating cost for a wastewater system. This is especially important for small-scale and onsite wastewater treatment systems, where sludge removal can be one of the few operating costs of the system. In 2000, as a result of a large number of septic system failures, the community of Wardsville installed a Clearford Industries Inc. Small Bore Sewer™ (SBS™) system which included two-chamber 3600 L tanks located on the properties of individual homes. The tanks were collectively attached to a small bore piping system to deliver the effluent from the tanks to a small community wastewater treatment system. During the summer of 2007, a field study was initiated with a community survey, followed by a review of candidate sites, leading to the selection of 29 sites for site investigation and sampling. Sampling involved the collection of samples for sludge characterization along with the measurements of the height of solids (scum and sludge) within the tank. The data were analyzed to determine the factors having a statistically significant impact on solids accumulation rates within each of the two chambers of the tank. Household water usage was found to be the variable having the strongest association with sludge and scum accumulation, and models were estimated relating solids accumulation to water usage in order predict pump out frequency. A second field sampling program was conducted in Wardsville during April 2008, involving only the first chamber of 13 primary clarifier tanks. Overall contributions have been made in understanding and quantifying solids accumulation rates and sludge characterization in onsite primary clarifier tanks. As well, the information gained from the analysis of the data collected provides a meaningful insight into the factors influencing solids accumulation within individual residential primary clarifier tanks, and points to future research directions for understanding the factors influencing solids accumulation. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-04-25 15:34:46.243

The urban sprawl creates a gap between producers and consumers and the a sustainable circuitof nutrients and energy is difficult to maintain. Many times the waste that is created in urbanareas is not reused and the circuit is lost. In this project, wastewater treatment is looked atwith the view point that resource recovery is possible through energy production and reuse ofnutrients. In order to optimally run each process step at a wastewater treatment plant forimproved resource recovery, more knowledge is needed in order to not disregard the finaleffluent quality. The goal of this project was to develop a model in MATLAB/Simulink for achemically enhanced primary clarifier at a wastewater treatment plant. The potential ofproducing more biogas and reducing the aeration energy needed in the biological treatmentstep was looked at by focusing on describing the settling velocity of suspended solids.Experimental analysis on settling properties for solids was performed on sampled wastewaterentering the primary settler after changing the addition of chemicals prior in the process line.The wastewater samples were homogenized and then rapidly vacuum pumped up in a column.The solids in the column could thereafter settle and was retained in a cup at the bottom. Themass of total suspended solids (TSS) was classified in five different settling velocity classes,each class assigned a characteristic settling velocity. The experimental procedure followed theViCA's protocol (French acronym for Settling Velocity for Wastewater). A settler, much likethe secondary settler in the Benchmark Simulation Model No. 2 (BSM2), a 10 layer nonreactivetank was modeled. The mass balance in each layer of the settler was decided by thevertical solid flux in the tank and built on the characteristic settling velocity gained from theexperiments. Re-circulation of excess sludge from the subsequent steps at the plant showed toeffect the settling properties of the sludge in the primary settler. The components of TSSshowed to have the largest effect on the distribution of settling velocity. The variation in doseof both coagulant and cationic polymer prior the primary settling tank showed to effect theparticle settling distribution somewhat. A first simulation with an applicable dynamic influentscenario was run. Despite any proper calibration the model gave fairly good predictions ofmeasured TSS in the effluent and sludge outtake water. / När urbana områden växer uppstår svårigheter i att bibehålla ett hållbart kretslopp av energioch näringsämnen. Avståndet mellan producent och konsument ökar och många gångeråteranvänds inte det avfall som städerna producerar och det hållbara kretsloppet bryts. Dettaprojekt har fokuserat på resursåteranvändningen i avloppsvattenhanteringen genommöjligheterna som finns i energiproduktion i form av biogas samt återanvändning avnäringsämnen genom slamåterförsel. Mer kunskap behövs inom varje processteg för attoptimalt använda avloppsreningsverk för förbättrad resurs-återvinning så att inte utgåendevattenkvalitet blir lidande. Målet med projektet var att utveckla en modell iMATLAB/Simulink för primärsedimentering med kemisk fällning. Experimentelltanalyserades sedimentationsegenskaperna hos primärslam genom provtagning avavloppsvatten inkommande till försedimenteringen efter tillsatser av fällnings-kemikalier.Proverna homogeniserades och vakuumpumpades sedan snabbt upp i en kolonn. Detpartikulära materialet i kolonnen kunde därefter sedimentera och fångades upp i en kopp ibotten. Den sedimenterade massan av totalt suspenderat material (TSS) klassificerades i femolika sedimenteringshastighetsklasser och varje klass tilldelades en karakteristisksedimentationshastighet Det experimentella förfarandet följde ViCA’s protokoll (franskförkortning för sedimentationshastigheter för avloppsvatten). En modell av ensedimentationstank, ungefär som för sekundär-sedimenteringen i Benchmark SimulationModel No. 2 (BSM2), utvecklades som en 10 lager icke reaktiv tank. Massbalansen i varjelager bestämdes av det vertikala flödet av partiklar och beräknades med de experimentelltframtagna karakteristiska sedimentationshastigheterna. Återcirkulering av överskottsslam frånde efterföljande reningsstegen visade sig ha stor påverkan på slammetssedimentationsegenskaper i försedimenteringen. Typen av TSS-komponenter hade den störstainverkan på fördelningen av sedimentationshastigheter. Variationen i dos av bådefällningskemikalie och katjonspolymer före primär-sedimenteringstanken hade en visspåverkan på fördelningen. En första simulering med ett sannolikt dynamisk inflödesscenariokördes. Utan någon riktig kalibrering av modellen gav den ändå en relativt realistisk prognospå TSS i utgående vatten och i slamuttaget. / I samarbete med forskningsgruppen ModelEAU, Quebec, Kanada

Wastewater compose an environmental risk as it contains high levels of nutrients, including phosphorus. Wastewater treatment plants (WWTPs) reduce phosphorus by using coagulants that precipitate soluble phosphate into metal phosphate, which is separated by settling. Coagulant flow is regulated by a control strategy, typically feedforward or feedback control. Feedforward is based on incoming wastewater disturbances whereas feedback control uses outgoing process values. Incoming phosphate is hard to measure and can be estimated using soft sensors. Modelling control strategies can help decide which strategy that is most suitable. Models describing phosphorus removal are Activated Sludge Model, ASM2d, and primary clarifier model. ASM2d models phosphorus precipitation and the primary clarifier model settling of particles. Tivoli WWTP faces challenges to reach effluent requirements of phosphorus. The wastewater flows through an equalisation tank, Regnbågen, before being pumped to Tivoli. Particulate matter settles in Regnbågen, which is removed by reducing the water level in Regnbågen. This rapidly increases incoming particulate load to Tivoli.Tivoli’s current control strategy is feedforward proportional to suspended solids. It is suspected, that this strategy overdose coagulant during the emptying of Regnbågen. The purpose of this thesis was to find the optimal control strategy for phosphorus precipitation at Tivoli WWTP, by using a model-based approach. Control strategies modelled are; feedforward, feedback and these two control strategies combined. Additional issues resolved are 1) calibration of a model that predicts the effect of chemical dosage on effluent phosphorus concentration from the primary clarifier, 2) calibrationof a soft sensor, 3) determination of which control strategy that is most suitable. ASM2d and a primary clarifier model were used to create a model describing chemical phosphorus removal. The calibration matches measured phosphate concentration, but underestimate peaks. The primary clarifier model was calibrated by minimising load differences for phosphate and total suspended solids, and was calibrated satisfyingly. A simplified soft sensor was constructed, described by a linear relationship between phosphate and pH. Three disturbances for feedforward control were analysed; measured phosphate, the soft sensors estimation of phosphate and Tivoli’s current controlstrategy. The optimal control strategy was found through a multi-criteria analysis. The optimal control strategy is the combined control strategy, when feedforward is proportional to incoming measured phosphate. The performance of all analysed feedforward disturbances were significantly improved when combined with feedback control. Furthermore, consequential errors are distinct when the soft sensor miss-predictincoming phosphate concentration. If the phosphate concentration cannot be correctly measured/estimated, feedback control alone has the best performance.