8 th IWA Specialist Group Conference on Waste Stabilization Ponds . 2 nd Latin-American Conference on Waste Stabilization Ponds Round Table Integration of ponds with other systems Belo Horizonte, April 2009 Carlos Augusto de Lemos Chernícharo Department of Sanitary and Environmental Engineering Federal University of Minas Gerais – Belo Horizonte - Brazil
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8th IWA Specialist Group Conference on Waste Stabilization Ponds
.
2nd Latin-American Conference on Waste Stabilization Ponds
Round TableIntegration of ponds with other systems
Belo Horizonte, April 2009
Carlos Augusto de Lemos ChernícharoDepartment of Sanitary and Environmental Engineering
Federal University of Minas Gerais – Belo Horizonte - Brazil
Brazilian and developing countries:
• Large pieces of flat land are not always available
• Enormous sanitation deficit
• Shortage of financial resources
• Lack of qualified operational personal
• Need of low cost, sustainable and simplified wastewater treatment systems
• Soil characteristics many times inappropriate for large natural systems, such as ponds and constructed wetlands
• Reuse still in early stages
Based on that scenario:
• Two process combinations have very interesting features:
• Quality of treated effluent is mainly regulated considering discharge and receiving body standards
• Compact anaerobic treatment systems can play a major role:
UASB + Polishing Ponds (PP)
UASB + Trickling Filters (TF)
UASB reactor is a very good alternative
Brief background on UASB reactors
Drawbacks and possible improvements
Examples of full-scale applications
Summary
Integration with Polishing Ponds
Integration with Trickling Filters
Final remarks
Brief background on UASB reactors
Main characteristics Advantages Applicability
Large urban areas
Small decentralized
systems
Small communities
No oxygen consumption
Low sludge production
Sludge is more concentrated and easy to dewater
Biogas production
Simple to operate
Lower O&M costs
Lower construction costs
Possibility of energy recovery
Anaerobic systems: general aspects
Brief background on UASB reactors
UASB Reactor
• The system is self-mixed by the upflow movement of biogas bubbles and by the liquid through the reactor, allowing the contact between the organic matter and the biomass. As a result, biogas is formed.
Brief background on UASB reactors
UASB Reactor
• The 3-phase separator is located in the upper part of the reactor, allowing the separation of gas, liquid and solids
Brief background on UASB reactors
UASB Reactor
• The settling zone allows the exit of the clarified effluent and the return of solids (biomass) to the digestion zone, in lower part of the reactor
Brief background on UASB reactors
UASB Reactor
• The UASB reactor functions, simultaneously, as a primary settler, as a biological reactor, as secondary clarifier and as sludge digester
• UASB reactor: main unit responsible for organic matter removal
• TF: complementary BOD and SS removal
• TF: poor coliform removal
• TF: good ammonia removal can be accomplished, but surface area and depth should be increased
Final remarks
Critical and important aspects in the selection of alternatives for wastewater treatment in developed and developing regions
Selection criteria for developed and developing countries
Developed countries Developing countriesEfficiencyReliabilitySludge disposalLand requirementsEnvironmental impactsOperational costsConstruction costsSustainabilitySimplicity
critical Important Important criticaladapted from von Sperling, 1996
Relative comparison of UASB/PP and UASB/TF treatment methods
Treatment system
EconomySustainability
Simplicity in O&M
Removal efficiencyReli-ability
Lower possibility of environmental problems
Requirements CostsBOD Nutrients Coliforms Bad
odours Noise Aerosol Insects wormsLand Energy Constr. O & M
+++++: most favourable +: least favourable ++++, +++, ++: intermediate grades, in decreasing order + / +++++: variable with land and soil characteristics
Both alternatives are very attractive for treating domestic wastewater in developing countries
Thanks for your attention
Scum accumulation on settling compartment
Scum accumulation inside the 3-phase separator
Waste gas
Biogas
FunBi
ogas
: micr
o-ae
ratio
n Biogas treatent
Heat
Electricity
Cogeneration of heat and electricity
Biofiltro
H2S and CH4 control in large WWTP
Biofilter
COD balance in UASB reactors treating domestic wastewater
Best situation
Conversion to CH4 and
recovery as biogas64%
Conversion to CH4 and loss with the liquid
phase8%
Losses with the gaseous
phase5%
Used for sulfate
reduction4%
Conversion to biomass
21%
Conversion to CH4 and
recovery as biogas23%
Conversion to CH4 and loss with the liquid
phase36%
Losses with the gaseous
phase5%
Used for sulfate
reduction16%
Conversion to biomass
21%
COD balance in UASB reactors treating domestic wastewater