• Document: EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT
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10th Specialized Conference on Small Water and Wastewater Treatment Systems Venice, 18-22 April 2011 EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT Marcos von Sperling Federal University of Minas Gerais Brazil EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT • Cover only wastewater treatment • Reflect more the experience at warm-climate regions, particularly Brazil • Express some personal opinions • Photos: not only small systems PRESENTATION OUTLINE • Stabilization ponds • Constructed wetlands • UASB reactors + post-treatment FEDERAL UNIVERSITY OF MINAS GERAIS - BRAZIL Centre for Research and Training in Sanitation UFMG - COPASA IWA SPECIALIST GROUPS WITH GREATER INTERFACE WITH EXTENSIVE AND NATURAL SYSTEMS • Anaerobic digestion • Resources Oriented Sanitation (EcoSan) • Sanitation and Water Management in Developing Countries • Small Water and Wastewater Systems • Use of Macrophytes in Water Pollution Control • Waste Stabilisation Ponds WASTE STABILIZATION PONDS IWA Specialist Group on Waste Stabilization Ponds 8 international conferences (next one: Adelaide, Australia, 1-4 August 2011) IWA Specialist Group on Waste Stabilization Ponds Books published by IWA on stabilization ponds STABILIZATION PONDS Facultative Brazil STABILIZATION PONDS Anaerobic pond – Facultative pond Brazil STABILIZATION PONDS Aerated lagoon South of France – Aerators on during wine production periods STABILIZATION PONDS Anaerobic – facultative - maturation ponds Northeast Brazil - 1 Anaer. pond + 1 Facult. pond + 3 Matur. ponds (100 ha) UASB – POLISHING PONDS Experimental WWTP UFMG/COPASA - 250 inhab REMOVAL OF ORGANIC MATTER FACULTATIVE PONDS FACULTATIVE PONDS Design criteria • Surface organic loading rate • Depth • Hydraulic retention time • Geometry (length / breadth ratio) FACULTATIVE PONDS Design criteria Surface organic loading rate - Ls Mara: Ls = 350 x (1.107 – 0.002.T) (T-25) (T = mean air temperature in coldest month) Surface loading rate as a function of temperature 400 Ls (kgBOD/ha.d) 300 200 100 0 10 12 14 16 18 20 22 24 26 28 30 Ls 100 124 152 183 217 253 291 331 350 350 350 T (oC) FACULTATIVE PONDS Effluent BOD Total BOD = Soluble BOD + Particulate BOD FACULTATIVE PONDS Hydraulic models Plug flow Completely mixed S = S 0 e -K.t S0 S= 1 + K.t Cells in series Dispersed flow S0 4ae1/2d S= S = S0 . t n (1 + a) 2 e a/2d − (1 − a) 2 e −a/2d (1 + K ) n a = 1 + 4K.t.d FACULTATIVE PONDS Effluent soluble BOD concentration Completely mixed: • Primary ponds: K = 0.30 to 0.40 d-1 • Secondary ponds: K = 0.25 to 0.32 d-1 FACULTATIVE PONDS Hydraulic models Relationship between reaction coefficients (K) FACULTATIVE PONDS Hydraulic models Tracer studies CFD modelling 25 (long time for field trials) 20 15 10 5 5 10 15 20 25 30 35 40 45 50 55 (e.g. studies on the influence of baffles) FACULTATIVE PONDS Effluent particulate BOD concentration No adequate models for predicting effluent BOD and SS 1 mgSS/L = 0.3 to 0.4 mgBOD5/L 1 mgSS/L = 1.0 to 2.0 mgCOD/L Pond effluents: 60 to 100 mgSS/L (for design) FACULTATIVE PONDS Effluent polishing (algae removal) Coarse rock filter: Experiments UFMG: Stones: 3 to 8 cm H = 0.40 m HLR: 0.5 to 1.5 m3/m3.d FACULTATIVE PONDS Effluent polishing (algae removal) Floating macrophytes – duckweed (Lemna) Experimental WWTP UFMG/Copasa PRIMARY FACULTATIVE PONDS Sand accumulation Brazil Prior grit removal is recommended FACULTATIVE PONDS Sludge accumulation Colombia F

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