Master In Civil Engineering Treatment PDF

MASTER IN CIVIL ENGINEERING Treatment, Reuse and Desalination Sep 2024 TRD 2024/25 Fonte: Águas públicas do Alentejo TRD 2024/25 Fonte: Águas Públicas do Alentejo TRD 2024/25 TRD 2024/25 TR...

MASTER IN CIVIL ENGINEERING Treatment, Reuse and Desalination Sep 2024 TRD 2024/25 Fonte: Águas públicas do Alentejo TRD 2024/25 Fonte: Águas Públicas do Alentejo TRD 2024/25 TRD 2024/25 TRD 2024/25 TRD - PROGRAM CHAP. 1 – Introduction to wastewater treatment: Solutions for urban and rural areas, individual and collective systems. Direct and indirect wastewater reuse for different end-uses: cleaning processes, irrigation and potable treatment. CHAP. 2 – Urban wastewater treatment: Domestic and industrial wastewater characterization; Treatment goals. Types of wastewater treatment plants (WWTP); Portuguese and international legislation. Wastewater treatment processes: preliminary treatment, decantation, biological treatment, deodorization, hydraulic circuits and hydraulic profile. Measurements and costs estimation. Advanced treatment processes: disinfection, ultrafiltration and membrane processes. Natural treatment systems. Individual treatment systems. TRD 2024/25 TRD - PROGRAM CHAP. 3 – Reuse systems: Historical perspective; In-situ water reuse; Reclaimed water for urban, agriculture and industrial ends. Health and environmental issues. Legal framework. Direct and indirect reuse for potable purposes. National and international case studies. Technologies and costs. CHAP. 4 - Desalination: Seawater characterization and potable water quality for human consumption. Main desalination processes. National and international case studies; Challenges and future opportunities. Sizing exercises and practical work TRD 2024/25 TRD 2024/25 WASTEWATER TREATMENT 1. Headworks (storm chambers, equalization basins, pumping station and preliminary treatment) TRD 2024/25 Typical WW treatment scheme Headworks TRD 2024/25 Typical WW treatment scheme Preliminary treatment TRD 2024/25 Typical WW treatment scheme Primary settling TRD 2024/25 Typical WW treatment scheme Secondary (activated sludge) TRD 2024/25 Typical WW treatment scheme TRD 2024/25 Typical WW treatment scheme TRD 2024/25 WATER THAT ARRIVES AT THE WWTP: Domestic wastewater Industrial Urban wastewater wastewater Stormwater TRD 2024/25 Urban wastewater: According to the Portuguese regulation, "urban wastewater is domestic wastewater or the mixture of domestic wastewater with industrial wastewater and/or rainwater runoff", where: domestic wastewater is defined as wastewater from residential facilities and services, mainly from human metabolism and domestic activities; and Industrial wastewater is all wastewater from industrial or commercial facilities that is not of domestic origin or rainwater runoff. TRD 2024/25 WW Treatment Goals: 1. Receive and treat urban wastewater or wastewater that, not originating in domestic activity, receives prior treatment that gives it identical characteristics. 2. Return the effluent wastewater to the water environment, in a controlled manner and with the necessary quality to ensure the sustainability of the ecosystem that receives it; 3. Manage and value the by-products that result from the treatment. TRD 2024/25  TRD 2024/25 Urban WW Characteristics They can lead to the development of sludge and the formation of anaerobic conditions with the consequent Suspended release of bad odors if released in an uncontrolled manner into the environment. solids Consisting mainly of proteins, carbohydrates and fats, their amount is measured indirectly through the lack of oxygen Organic matter in the water. When discharged into the natural environment, the biodegradation of organic matter can lead to local oxygen depletion and the formation of anaerobic conditions. Pathogenic Contagious and potentially fatal diseases for humans and animals can be transmitted by pathogenic microorganisms microorganisms present in water. Both nitrogen and phosphorus, together with carbon, are essential elements for natural development. When discharged Nutrients uncontrollably into the aquatic environment, they can lead to excessive algae formation (eutrophication). They can also cause groundwater pollution. Priority Potentially carcinogenic, mutagenic, teratogenic or highly toxic compounds present in wastewater, contact with which pollutants may cause serious problems for human health. Persistent These components tend to resist conventional treatment processes, so they require special attention. These are organic usually surfactants (substances that influence the contact surface between two liquids), phenols and agricultural pollutants pesticides. They are usually added to urban wastewater by industries or commercial activities and have to be removed from the Heavy metals water whenever there is reuse. Dissolved Inorganic constituents such as calcium, sodium and sulfates are added to water by virtue of its use in regular human inorganic activities and must be removed when the water is intended for reuse. constituents TRD 2024/25 Typical WW treatment scheme https://www.youtube.com/watch?v=FvPakzqM3h8 TRD 2024/25 The average annual daily flow of domestic wastewater (Q) is : Q = f x Pop. x Capitation Being f the factor of inflow to the network and capitation the consumption of drinking water per inhabitant. For sizing purposes, whenever the average annual daily flow is used, it is necessary to consider the increase corresponding to the entry of rainwater (undue inflows), since they are not included in this equation. The instant flow (QP) tributary to the WWTP is given by the following equation: QP = FP x Q + Qinf + Qesp Being: ▪ FP the peak-hour factor which, in the absence of local records can be estimated on the 60 basis of the regulation Portuguese in force: FP = 1,5 + 𝑃 with P equal to the population to serve; ▪ Q the average annual daily flow of domestic waste water; ▪ Qinf the infiltration flow rate; ▪ Qesp flow resulting from special installations (e.g. large industrial units). TRD 2024/25 TRD 2024/25 Typical WW treatment scheme Preliminary treatment TRD 2024/25 Headworks: Storm chambers Objective: to minimize the occurrence of flow peaks from very intense rainfall, which can wreak the treatment on downstream treatment NOTE: Excess flows are discharged into the receiving water environment with low concentrations of pollutants. TRD 2024/25 Storm chambers Objective: to minimize the occurrence of flow peaks from very intense rainfall, which can wreak the treatment on downstream treatment  TRD 2024/25 Parshall channel Dimension-specific structure that allows instantaneous measurement of flows through an ultrasonic meter associated with a free surface flow normalized by the channel cross-section. ETAR Areinho (Nov19) It is also often used at the end of the treatment line to quantify the water discharged into the receiving medium and used for rapid mixing of chemicals. Depending on the flow rate to be measured, they can be manufactured on site, in reinforced concrete or prefabricated in FRP (fiberglass reinforced polyester), and it is convenient to install duly certified models.  TRD 2024/25 Parshall channel ▪ Converging Section- Reduces flow velocity at the inlet, decreasing the possibility of turbulence and increasing the accuracy capability of the measuring equipment. ▪ Throttling Section(Throat) - Second section of the equipment, where the water is subjected to a concentration produced by the narrowing of the sides and/or by the elevation of the bottom of the channel. ▪ Enlargement Section - Positioned at the end of the equipment, after its narrowing of the channel, it aims to provide the normalization of the flow in the channel. Fonte: www.contimetra.com TRD 2024/25 Parshall channel The flow measurement follows the readings of the installed level meter and the application of the flow law indicated by the manufacturer, which is usually of the type: Q = C x han Where Q is the flow (m3/s), ha the height of water upstream of the throttled section (m) and C and n the coefficients relative to the shape of the channel: CANAL W (mm) C n 1” 25 0,338 1,555 2” 51 0,676 1,555 3” 76 0,992 1,55 6” 152 2,060 1,58 9” 228 3,070 1,53 2” 305 3,950 1,55 TRD 2024/25 https://www.youtube.com/watch?v=bxHagMo6nm0 TRD 2024/25 Equalization tank Goal: to regulate the influent flow peaks to the WWTP. Sizing: balance between the daily volume of affluent and effluent, and the effluent flow is the average daily flow that reaches the WWTP. The regularization capacity is the biggest difference between the two accumulated flow curves.  TRD 2024/25 Excel Equalization tank Example: It is estimated that a certain WWTP presents the following variation in the tributary flows. What is the volume of the equalization tank to be installed? fh V (afl) H QMDA (m3/d) hora Dom Hotéis Com Escolas Infiltr m3/h ano H 1 0,00 0,00 0,04 0,02 0,04 41,5 2 0,00 0,00 0,03 0,02 0,04 42,5 Doméstico 1934,5 3 0,00 0,00 0,04 0,02 0,04 65,7 Hotéis 514,0 4 0,00 0,02 0,05 0,02 0,04 45,2 Comércio 117,3 5 0,00 0,03 0,04 0,02 0,04 49,5 Escolas 155,9 6 0,01 0,03 0,03 0,02 0,04 73,7 Infiltr 816,5 7 0,07 0,10 0,02 0,02 0,04 219,1 8 0,13 0,10 0,01 0,02 0,04 346,2 9 0,08 0,10 0,02 0,04 0,04 245,5 Variação horária estimada 10 0,05 0,05 0,03 0,06 0,04 171,3 11 0,05 0,03 0,03 0,07 0,04 157,0 400,0 12 0,04 0,02 0,03 0,09 0,04 130,6 350,0 13 0,05 0,01 0,05 0,07 0,04 147,5 14 0,07 0,02 0,05 0,07 0,04 184,6 300,0 15 0,03 0,03 0,05 0,06 0,04 122,2 250,0 16 0,02 0,03 0,07 0,09 0,04 103,2 17 0,03 0,03 0,07 0,08 0,04 109,3 200,0 18 0,04 0,03 0,06 0,05 0,04 129,4 150,0 19 0,07 0,20 0,05 0,05 0,04 270,8 20 0,08 0,08 0,04 0,03 0,04 234,1 100,0 21 0,10 0,02 0,04 0,03 0,04 234,1 50,0 22 0,05 0,04 0,04 0,03 0,04 157,3 0,0 23 0,03 0,04 0,04 0,03 0,04 116,7 0 5 10 15 20 24 0,01 0,00 0,05 0,03 0,04 62,5 TRD 2024/25 Pumping station Goal: ensure sufficient hydraulic load for the entire downstream process to occur gravitationally. Arquimedes screw: ETAR Espinho (Mai13) TRD 2024/25 Pumping station Goal: ensure sufficient hydraulic load for the entire downstream process to occur gravitationally. Arquimedes screw : ETAR Ave (Mai21) TRD 2024/25 Pumping station Goal: ensure sufficient hydraulic load for the entire downstream process to occur gravitationally. Arquimedes screw : https://www.youtube.com/watch?v=6mBcanTCVLY TRD 2024/25 Pumping station: Submersible Pumps Pdf Dwg TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Pdf Dwg Example: TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Ave (Mai21) TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Freixo (Out21) TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. www.youtube.com/wat ch?v=ps0hkOy3Ctk TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Ave (Mai21) TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Ave (Mai21) TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Freixo (Sett21) TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Ave (Mai21) TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. ETAR Freixo (Set21) http://wamgroup.com.br/pt-BR/WAMBR/Product/GRITSEP%20FGC/Classificador-de-Areia-da-Dinamica-de-fluidos TRD 2024/25 Preliminary treatment Goal: removal of suspended solids and attribute to the wastewater characteristics that enable its discharge in the downstream treatment process. Harrowing or screening; Tamisation; Sand and oils/fats removal. TRD 2024/25 WASTEWATER TREATMENT 2. Primary treatment TRD 2024/25 Primary treatment TRD 2024/25 Typical WW treatment scheme Primary settling TRD 2024/25 Primary treatment Marecos do Monte, H., & Albuquerque, A. (2013). Reutilização de Águas Residuais. Série Guias Técnicos - ISEL e ERSAR. TRD 2024/25 Primary treatment Initially the only type of treatment when the first sanitation infrastructures began to appear in urban areas. Nowadays, this stage alone does not meet the legal requirements for water quality, so additional downstream treatment processes are always required. TRD 2024/25 Primary treatment Initially the only type of treatment when the first sanitation infrastructures began to appear in urban areas. Nowadays, this stage alone does not meet the legal requirements for water quality, so additional downstream treatment processes are always required. TRD 2024/25 Primary treatment In the primary decanter, the solids present in the wastewater that were not removed in the preliminary stage are separated, namely suspended solids, sedimentable solids, dissolved solids and colloidal solids. At the bottom of this decanter, primary sludge is produced, which must be frequently removed to avoid the formation of anaerobic conditions in this location. A more clarified effluent with less organic matter passes downstream, since, under normal conditions, these decanters can remove between 20 and 60% of TSS and 33 to 38% of BOD. TRD 2024/25 Primary treatment Pdf Dwg TRD 2024/25 Primary treatment TRD 2024/25 Primary treatment https://www.youtube.com/watch?v=a1D0fv4zDh4 WASTEWATER TREATMENT 3. Secondary treatment TRD 2024/25 Fonte: Águas Públicas do Alentejo TRD 2024/25 SECONDARY TREATMENT: Goals: 1. Transforming biodegradable organic matter into easy-to-manage products; 2. Remove and aggregate non-sedimentable suspended solids into flakes or biofilms; 3. Transform or remove nutrients (nitrogen and phosphorus). TRD 2024/25 SECONDARY TREATMENT: Types: 1. physicochemical processes (coagulation/flocculation + decantation) 2. Biological processes (followed also by decanting). Biologics are more common because they have lower costs with reagents, and treatment by chemical means also has the disadvantage of generating chemical by-products in the treated water TRD 2024/25 SECONDARY TREATMENT : Types: 1. physicochemical processes (coagulation/flocculation + decantation) 2. Biological processes (followed also by decanting). Reduction of organic matter is done by the action of microorganisms (bacteria) Biologics are more common because they have lower costs with that digest organic matter in the presence of oxygen and nutrients (nitrogen and reagents, and treatment by chemical means also has the phosphorus) and thus produce biomass, carbon dioxide, water and other disadvantage of generating chemical by-products in the products: treated water COHNS (substâncias orgânicas biodegradáveis) + O2 + bactérias → CO2 + H2O + NH3 + outros produtos (sais) + energia TRD 2024/25 BIOLOGICAL PROCESSESS TRD 2024/25 ACTIVATED SLUDGE TRD 2024/25 ACTIVATED SLUDGE TRD 2024/25 ACTIVATED SLUDGE Sizing: Prolonged Parameter Conventional aeration Hydraulic retention time [h] 6 a 12 18 a 30 Sludge concentration in the aeration 1500 a 2500 3000 a 5000 tank [mg MLSS/L] (1) Mass organic load [kg CBO/kg MLSS/d] 0,1 a 0,3 0,05 a 0,1 Ratio MLVSS/MLSS 0,89 a 0,90 0,75 a 0,80 Age of the sludge [d] 4a7 12 a 20 TRD 2024/25 ACTIVATED SLUDGE Sizing: The oxygen requirement in the water to be treated is the sum of the oxygen required for each of the following processes: BOD removal; Oxidation of ammonia nitrogen; Endogenous respiration. TRD 2024/25 ACTIVATED SLUDGE Recirculation flow: Qr = QX / (Xr – X) TRD 2024/25 ACTIVATED SLUDGE IMP: Being a natural process, local temperature conditions (preferably between 10 and 30 ºC) and pH (6.5 to 8.5) or the appearance of inhibiting substances can make treatment unfeasible, which often leads to problems with sludge decantation in the SD. TRD 2024/25 ACTIVATED SLUDGE https://www.youtube.com/watch?v=ciPFC3Y2rkg&t=235 s TRD 2024/25 ACTIVATED SLUDGE In the SBR process, the aeration and sludge decantation are carried out in the same tank in a cyclical manner. This system does not need recirculation of biological sludge, as there is no loss of biomass in the aeration zone. It has great flexibility and capacity to absorb load fluctuations, ensuring high removal efficiencies. ETAR de Paço de Sousa, Penafiel. TRD 2024/25 SBR (SEQUENCING BATCH REACTOR): https://www.youtube.com/watch?v=amCWFbPiZSs &t=92s TRD 2024/25 WASTEWATER TREATMENT 4. Natural treatment systems TRD 2024/25 Natural wastewater treatment systems Lagoon system Systems consisting of ponds in which wastewater is treated by entirely natural methods with the intervention of algae and bacteria. Low degree of oxidation of this water (compared to traditional processes where aeration is controlled), thereby: high HRT! The composition of the biological community in a wastewater treatment pond is determined by the applied organic load, the weather conditions and the hydraulic retention time. TRD 2024/25 Natural wastewater treatment systems Lagoon system Taking into account the influence of the climatic conditions of the places where they are built and the low mechanization of the treatment, it is not possible to define universal criteria for sizing and operation for these ponds. The specialist literature presents recommended ranges, and is unanimous in the need to include a high degree of preliminary treatment (removal of sand, grease and suspended solids), as well as versatile hydraulic circuits for flexible operation. TRD 2024/25 Natural wastewater treatment systems Lagoon system https://www.youtube.com/watch?v=Mh6wJa8kc7I TRD 2024/25 Natural wastewater treatment systems Lagoon system Typical Lagoon system: Anaerobic lagoons + Organic matter and TSS removal Facultative lagoons + Maturation lagoons Microorganisms removal TRD 2024/25 Natural wastewater treatment systems Lagoon system Typical Lagoon system: Anaerobic lagoons + Facultative lagoons + São do tipo fotossintético Maturation lagoons TRD 2024/25 Natural wastewater treatment systems Lagoon system Very efficient process, which allows a removal of more than 90% of TSS, BOD and ammonia. It is also efficient in eliminating pathogenic organisms, unlike conventional treatments that require a specific disinfection step to do so. TRD 2024/25 Natural wastewater treatment systems Lagoon system Deodorization: well-dimensioned systems with good operation and maintenance, do not have a significant release of bad odors. The large areas required for the lagoons and the contact with atmospheric air end up creating a significant dispersion effect. The control of the effluent flows and the minimization of the risk of overloading the system are essential for the release of odors to remain at satisfactory levels. TRD 2024/25 Natural wastewater treatment systems Lagoon system Effluent quality: discharge with high concentration of BOD and TSS mainly due to the algae that are in the process. NOTE: In a typical BOD laboratory analysis, the algae end up consuming much of the oxygen, since incubation takes place in a dark environment, without sunlight. But... The presence of algae has a beneficial effect if used for agricultural irrigation (algae are natural fertilizers that increase the organic content of soils and help with their water retention capacity). TRD 2024/25 Natural wastewater treatment systems Lagoon system In addition to the typical system built by the 3 ponds, there are also the so- called aerated ponds: Secondary treatment systems for activated sludge but without sludge recirculation, with a hydraulic retention time ranging from 2 to 6 days. They are equipped with mechanical aerators or diffusers, which guarantee the oxygenation of the water so that the process of degradation of organic matter can be processed more quickly. www.fuchswater.com TRD 2024/25 Natural wastewater treatment systems Lagoon system In addition to the typical system built by the 3 ponds, there are also the so- called aerated ponds: They can treat wastewater after preliminary treatment, or waters subject to primary treatment (anaerobic ponds, for example). Their concentration of activated sludge is lower than typical systems and they do not have the capacity to remove microorganisms, so in this case they must have a tertiary disinfection treatment. TRD 2024/25 Natural wastewater treatment systems Lagoon system TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) TRD 2024/25 Natural wastewater treatment systems Lagoon system – 1. Anaerobic lagoons TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag)  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 1. Anaerobic lagoons They are 2 to 5 m deep and receive such a high organic load (>100 g BOD/m3 day) that they contain no dissolved oxygen or algae, although occasionally a thin layer of Chlamydomonas may appear on the surface. TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag)  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 1. Anaerobic lagoons Its function is similar to that of septic fosses, with the main objective being the removal of BOD, obtained through the sedimentation of decantable solids and the consequent anaerobic digestion of these sludges. Anaerobic microorganisms convert organic matter into stable substances such as carbon dioxide and methane (CO2 and CH4, respectively). TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag)  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 1. Anaerobic lagoons The microorganisms that act in this lagoon are the same as those of a typical treatment by activated sludge in a conventional WWTP, therefore, they are subject to the same constraints (especially the pH, which cannot be lower than 6.2). TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) TRD 2024/25 Natural wastewater treatment systems Lagoon system – 1. Anaerobic lagoons The performance of Anaerobic lagoons increases significantly with temperature: TRD 2024/25 Natural wastewater treatment systems Lagoon system – 1. Anaerobic lagoons BOD reduction is important to determine the organic load affluent to the next process (facultative lagoon). The temperature to be considered in the design must correspond to the most unfavorable situation, and it is common to admit the average temperature of the coldest month in the place. This is a conservative consideration, since the water temperature is usually 1 to 2ºC above the air temperature, in the coldest month. The gradual accumulation of digested solids at the bottom of Anaerobic lagoons requires collection with a recommended frequency of 1 to 3 days. TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag)  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons Facultative lagoons can receive wastewater after preliminary treatment and water from Anaerobic lagoons. Its main function is, as mentioned, the removal of BOD from the wastewater to be treated, but through a lower surface load (100 to 400 kg/ha/d) when compared to anaerobic water. TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag)  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons This reduced surface load will allow the development of algae that will be the main agents of the treatment that takes place in them. The hydraulic retention time is around 20 days, and can reach 180 days in cold climates. TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag)  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons As a result of the photosynthetic activity of the algae, there is a daily variation in the concentration of dissolved oxygen:  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons As a result of the photosynthetic activity of the algae, there is a daily variation in the concentration of dissolved oxygen: From sunrise, the concentration of dissolved oxygen gradually rises due to the photosynthetic activity of the algae reaching its maximum level in the middle of the afternoon.  TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons As a result of the photosynthetic activity of the algae, there is a daily variation in the concentration of dissolved oxygen: From there, it drops to a minimum recorded throughout the night, when photosynthesis ends and the bacteria's respiratory activity ends up consuming much of the oxygen. TRD 2024/25 Natural wastewater treatment systems Lagoon system – 2. Facultative lagoons https://www.youtube.com/watch?v=fx0GMhIMIy0 TRD 2024/25 Natural wastewater treatment systems Lagoon system – 3. Maturation lagoons TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) TRD 2024/25 Natural wastewater treatment systems Lagoon system – 3. Maturation lagoons The main purpose of a maturation pond is to eliminate pathogenic microorganisms, such as fecal coliforms and viruses that may be present in the wastewater discharged by facultative lagoons. TRD 2024/25 Natural wastewater treatment systems Lagoon system – 3. Maturation lagoons These ponds remain fully aerobic due to the low influent organic load and the shallow depth of water (< 1 m). As in the facultative lagoons, the microbiological activity of the maturation lagoons, It is based on the symbiosis between algae and bacteria. TRD 2024/25 Natural wastewater treatment systems Lagoon system – 3. Maturation lagoons Despite their high efficiency, they have the disadvantage of occupying a large area (they can occupy twice the surface area of an facultative pond). TRD 2024/25 Natural wastewater treatment systems Lagoon system – 3. Maturation lagoons TRD 2024/25 Natural wastewater treatment systems MACROPHYTE SYSTEMS ETAR de Vila Fernando (Elvas) TRD 2024/25 Natural wastewater treatment systems MACROPHYTE SYSTEMS - Macrophyte beds (designated in international literature by constructed wetlands) are nature-based systems that mimic and enhance the action of swampy areas in the purification of the water that flows into them. These beds are secondary treatment units that must contemplate an upstream primary treatment stage (septic tank or anaerobic lagoon) to retain solids that would otherwise end up filling the bed and making treatment unfeasible. TRD 2024/25 Natural wastewater treatment systems MACROPHYTE SYSTEMS These beds can be of different types. Floating aquatic plant systems are not common, not least because of their difficult maintenance, taking into account that the type of plants characteristic of these systems (such as water hyacinth, duckweed, among others) have a very intense proliferation. TRD 2024/25 Natural wastewater treatment systems Macrophyte beds – Floating aquatic plant systems They can be found in WWTP by Lagoon system (a consequence of this type of treatment) or in polluted water lines. WWTP of this type are not common. TRD 2024/25 Natural wastewater treatment systems Macrophyte beds The macrophyte beds of: submerged aquatic plants (or free-flowing); horizontal subsurface flow; or Vertical subsurface runoff … have plants of different species, which can be installed in soil or in a layer of gravel. TRD 2024/25 https://www.youtube.com/watch?v=Draeex1eOnE TRD 2024/25 Natural wastewater treatment systems Macrophyte beds – Rooted aquatic plants  TRD 2024/25 Natural wastewater treatment systems Macrophyte beds – Rooted aquatic plants The element that contributes most to the purification of influent waste water is: soil or the layer of gravel where the plants are rooted. (the action of plants is, however, fundamental for the removal of nutrients, especially Nitrogen). TSS present in wastewater are retained in the support medium (soil or gravel) or deposited by settling. Ammonia is removed by several factors, including nitrification (and subsequent denitrification), absorption by plants and the accumulation of organic nitrogen in the decanted sediments. Almost total microbiological removal efficacy is also reported, especially for helminth eggs.  TRD 2024/25 Natural wastewater treatment systems Macrophyte beds – Plantas aq. enraizadas Rectangular basins or shallow trenches, filled with growth medium and support for plants (usually soil with a high portion of sand) and the bottoms waterproofed by plastic screens similar to those used for the same purpose in the previously mentioned ponds. In order to facilitate the maintenance operation, the beds are multicellular equipped with effluent distribution and effluent collection structures. From an engineering point of view, the macrophyte bed is a treatment process governed by natural conditions that has very little leeway in relation to its treatment effectiveness. Consequently, macrophyte bed system design, like other natural treatment systems, must have considerations directed at maximum removal of suspended solids from the influent (preliminary and primary treatment) and versatile hydraulic operation (recirculation). TRD 2024/25 https://www.youtube.com/watch?v=arVtT-RCc7k TRD 2024/25 Natural wastewater treatment systems Macrophyte beds – Preliminary treatment TRD 2024/25