Water and Wastewater Treatment Systems

Basic knowledge of mathematics, physics, chemistry and biochemistry.

In order to achieve the objectives of the course unit and to provide the students with the expected competences, the teaching learning process is based on

a) on the study of specific cases which is supported by a set of instructions that lead the student to analyze them, draw conclusions and make decisions or suggest actions;

b) in the execution of practical exercises to apply the theoretical concepts;

c) in the bibliographical research needed to complement the information obtained in class.

Students should acquire the following competences by demonstrating:

–        To know the principles of operation of each unit operation/process.

–        To know the design, functioning and operation criteria associated to each treatment stage.

–        To know the main tertiary treatment systems and the need to valorize waste and wastewater.

–        Apply the previous concepts to the efficient management of WTP and WWTP.

WATER TREATMENT SYSTEMS

In this scope the following subjects will be addressed:

Softening – Definition of alkalinity and hardness of water and its origin. Types of hardness and units in which it can be expressed. Treatment processes. Process of softening by precipitation. Determining the amount of chemicals to be used in the treatment: bar diagram. Stabilization of water. Equilibrium pH and indices for classifying water: Langelier Index and Ryznard Index. Operative considerations;

Sedimentation – Description of the movement of particles within a fluid under the action of gravity. Types of sedimentation: discrete, flocculent, impeded and thickening. Discrete sedimentation: Stokes equation and notion of terminal velocity; sizing of sedimentation/decantation basin; notion of hydraulic surface load; calculation of removal efficiency of suspended particles. Flocculent sedimentation: flocculent sedimentation test; calculation of removal percentage. Impeded sedimentation; description of an impeded or zonal sedimentation test; curve interface height versus time. Primary and secondary sedimentation in the context of wastewater treatment systems: objectives, working principle and criteria for sizing.

Filtration – Basic concepts: filtration mechanisms, filtering media, operation modes and filter types. Head losses in a filter bed and dimensioning of filtration units;

Disinfection – Methods of disinfection. Mechanisms of action of disinfectants and factors that influence their action. Specific application of disinfection with chlorine compounds: chlorine demand curve (breakpoint curve), determination of the “breakpoint” point and sizing of the mixing and contact chamber.

WASTEWATER TREATMENT SYSTEMS

Preliminary and primary treatment – Concepts of inlet and primary sedimentation: design and operation criteria;

Secondary treatment – Basic concepts of microbial kinetics in aerobic processes. Activated sludge systems: characteristics, criteria and design equations. SBR (batch reactor sequence) systems as derived systems from the conventional activated sludge process: definition of operating cycle, sludge removal, design criteria and equations, advantages and disadvantages. Oxygen transfer in wastewater: transfer coefficient in clean water and wastewater, effect of temperature and water characteristics. Mechanical and air diffusion aeration systems (surface and submerged).

Some operational problems in aerobic biological suspended biomass systems and their control measures.

Tertiary treatment – Nutrient removal from wastewater: Nitrification/ denitrification processes: fundamentals, advantages and drawbacks, external carbon sources; increased biological removal of phosphorus and physic-chemical removal: – coagulation-flocculation, basic concepts and mechanisms of coagulation and flocculation. Operative considerations. Concepts associated with agitation and mixing- Jar test. Most used coagulation-flocculation agents and selection criteria. Integration of the process in the sequence of treatment of wastewater and drinking water. Flocculators types.

Recovery of phosphorus and its valorization as a fertilizer. Factors on which its recovery depends.

Reuse of treated urban wastewater for irrigation and treatment and valorization of sludge and agricultural waste. Applicable legislation and the need to control priority and emerging pollutants in sludge and water.

• - frequência 2 - 50.0%
• - frequência 1 - 50.0%

• - exame escrito - 100.0%

NAO

1. Metcalf & Eddy. Wastewater engineering: treatment and reuse. 4th Ed. McGraw HillInternational Editions. New York. 2003.

2. Sincero, a. P., Sincero, G.. “Physical-Chemical Treatment of Water and Wastewater. CRCPress, 2003.

Handouts and other documentation provided by teachers.