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Tratamiento Fisico-Quimico

CEPT Schematic

Source: Prof. Harleman, MIT

Bench-Scale CEPT

Source: Prof. Harleman, MIT

CEPT: TSS vs OFR

Source: Prof. Harleman, MIT

CEPT: BOD vs OFR

Source: Prof. Harleman, MIT

CEPT Sludge

Source: Prof. Harleman, MIT

Sludge Reuse Example

1. Sludge removal is ~10% more than solids removed (1/3 in form of ferric phosphate precipitate, and 2/3 in form of ferric hydroxide precipitate)

2. CEPT sludge has a 4~6% solids content3. Lime stabilization/disinfection (2 hours contact

time at a pH>12)4. Gravity thickening5. Sludge drying beds6. Agricultural application Source: Prof. Harleman, MIT

Secondary Treatment Equivalent Quality Effluent by Physico-Chemical Treatment

Preliminary Treatment byRotating Screens and Vortex Grit Chamber

Preliminary Treatment byRotating Screens and Vortex Grit Chamber

Chemically EnhancedPrimary Treatment

(CEPT)

Rapid Sand Filtration or

Membrane Microfiltration

UV Disinfection

Effluent of Secondary Level Quality Without Biological Treatment

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Rotating Screens Treatment withRotating Screens Treatment withOrganic Coagulants

Sea- and River Outfall

•0.2 mm mesh sieve with organic coagulants may achieve reduction of more than 75% of total COD

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Results of HRS, 0.2 mm Screensof HRS, 0.2 mm Screens

Sea- and River Outfall

•Reduction of 50% of particular COD

•Reduction of of 30% of total COD

•With organic coagulants: Reduction of more than 75% of total COD

A process Worth Investigating

Preliminary Treatment byRotating Screens and Vortex Grit Chamber

Preliminary Treatment byRotating Screens and Vortex Grit Chamber

Rapid Sand Filtration or

Membrane Microfiltration

UV Disinfection

Effluent of Secondary Level Quality Without Biological Treatment

Organic Coagulants

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Comparison of Costs Preliminary Treatment to that of Activated Sludge(Ratio of Cost in Relation to Activated Sludge)

0.11.0O&M

0.11.0Investment

Preliminary Treatment

Activated Sludge

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Comparison of Costs of Various Types of Physico-Chemical Treatment(Ratio of Cost in Relation to Activated Sludge)

0.50.50.50.51.0O&M

0.40.180.50.251.0Investment

CERFS+Filtration+Disinfection

CERFSCEPT+Filtration+Disinfection

CEPTActivated Sludge

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Conclusiones: Tratamiento de Aguas Residuales en Paises en Via de Desarrollo

The Strategy in Developing Countries should be to adopt reasonable standards for effluent quality, which are flexible in terms of quality and timing, i.e., which permits development in stages and which take into account the assimilation capacity of the receiving bodies. Relaxed Standards and development in stagesDeveloping countries should use appropriate technology for wastewater treatment, based on simplified processes which are less costly than conventional processes in terms of investment as well as operation and maintenance, simple to operate and have the capacity of yielding the required effluent quality. Appropriate TechnologyIn view of population growth forecasts in Developing Countries and scarcity of financial resources, wastewater treatment has a chance only if innovative, affordable (low investment and O&M costs) and easy to operate processes will be developedSuch types of processes are mainly preliminary treatment (when that level of treatment is sufficient) and physicochemical treatment

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Conclusiones: Tratamiento Previo a la Descarga de aguas Residuales al Mar por Medio de Emisarios Submarinos

La amplia experiencia acumulada en el mundo y las nuevas guias de la OMS indican que, al utilizar un emisario efectivo, tratamiento preliminar antes de la descarga del efluente al mar es un nivel de tratamiento suficiente La nueva tendencia en plantas de tatamiento preliminar es el uso de desarenadores tipo vortex y militamices giratorios inovativosSi las normas especificas del pais requieren un nivel de tratamiento mas alto del preliminar, se debe construir el sistema en etapas, siendo la primera etapa el tratamiento preliminar seguido por un emisario efectivoLas siguinetes etapas de tratamiento deben consistir

de tratamiento Fisico-Quimico, y no biologico areobio

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Conclusions (Cont.)Opposition in developing countries to wastewater disposal through a submarine outfall following preliminary treatment will often prevent any progress towards improving wastewater disposal. This is because treatment above and beyond preliminary would render most projects financially non-viableAvoidance of actions towards solving wastewater disposal problems is the worst option of all, and usually leaves the most vulnerable population (mostly the poor) under the worst conditions

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Significance of Outfalls for Coastal Cities in Developing Countries

Submarine Outfalls for wastewater discharge provide an excellent and affordable solution for coastal cities in developing countriesOnly preliminary treatment needs to be provided (with an outfall design compatible with such treatment) and monitoring needs to be undertakenA more elevated treatment level should be provided only if monitoring results indicate that such treatment is necessary