ASSESSMENT OF DECENTRALIZED WASTEWATER TREATMENT SYSTEMS IN THE RURAL AREA OF CUENCA, ECUADOR.

Transcription

1 ASSESSMENT OF DECENTRALIZED WASTEWATER TREATMENT SYSTEMS IN THE RURAL AREA OF CUENCA, ECUADOR. Andres Alvarado Martinez Departamento de Recursos Hídricos y Ciencias Ambientales idrhica FACULTAD DE INGENIERÍA UNIVERSIDAD DE CUENCA

2 content Introduction Cuenca and the rural systems Long term objectives Problem Statement / Objectives Methods Information analysis Characterization Results / discussion Conclusions / perspectives

3 introduction objective methods results conclusions CUENCA ECUADOR 0.5 million inhabitants, third largest city of Ecuador Ecuadorian leader in sanitation services: 95% sewerage; 90% wastewater treatment (WSP)

4 introduction objective methods results conclusions Ucubamba WSP, The biggest WWTP in ECUADOR DBO=85%, sólidos=95%, Patógenos= log7 log4 Remoción en línea de lodos (203)

5 introduction objective methods results conclusions The Decentralized Systems 32 systems. Constructed in the last 20 years. Located in rural areas Serving around inhabitants

6 introduction objective methods results conclusions The Decentralized Systems Problem statements: The systems are progressively abandoned There were inconsistencies in the efficiencies reported A preliminary inspection showed collapsed systems and very low biological activity in others Objective: a real assessment of the systems as baseline for taking decisions about the sanitation of the rapid urbanization in the surroundings of Cuenca Methods: analysis of the information supplied by the agency, inspections and characterization

7 introduction objective methods results conclusions Analysis of the information of the agency: Systems deteriorated or with very low biological activity reported very good efficiencies efficiency 00 $$$ 50 Only physical removal of particulate organics Physical and biochemical stabilization of organics Rebuilding filters month

8 Nº Access Roads Served Area Altitude T ha m.a.s.l C O&M Plan Preliminary Treatment Primary Treatment Secondary Treatment By-Pass Screen Grit Cham ber Type Chamber L;W;D [m] Typenumber Filter Media L;W;D [m] Sludge drying bed Final Disposal OS --- ST 2 N/D FWSW N/D Stream 4 N/D OS ST 2 N/D FWSW N/D TL OS --- ST 2 N/D FWSW N/D TL OS --- ST 2 N/D FWSW- --- N/D Infil OS --- ST 2 N/D HF/AF Gravel --- TL 8 N/D OS --- ST 2 N/D FWSW- --- N/D Stream N/D ST 2 N/D VF/AF Gravel Stream N/D N/D ST N/D HF/AF N/D N/D N/D ST N/D HF/AF N/D N/D OS ST 2 N/D Stream N/D ST N/D AF/-- N/D N/D ST 2,9;3,4;2,5 FWSW ,5;20,2;,8 Stream OS ST 2 N/D VF/AF Brick --- Stream ST 2 N/D VF/AF Gravel --- Stream OS --- UASB 3 N/D HF/AF Gravel --- Stream N/D OS --- ST 3 7,3;3,0;2,9 FWSW ,7;8,7;2,5 Stream ST 2 N/D VF/AF Brick Stream OS --- ST 2 N/D VF/AF Brick --- Stream ST 2 N/D VF/AF Brick Stream OS ST 2 9,4;3,;,5 VF/AF Brick --- Stream OS --- ST 2 9,4;3,0;,5 VF/AF Gravel Stream OS --- ST 2,;4,3;2,7 VF/AF Brick 2,5 Di 3,3 D Stream OS ST 2 9,4;3,;,5 VF/AF Brick --- Stream ST 2 N/D HF/AF Gravel Stream ST 2 7,6;2,9;2,9 HF/AF Gravel 7,6;2,9;2,9 --- Stream ST 2 N/D VF/AF Gravel --- Stream N/D ST 4 4,8;4,7;, Stream OS --- ST 2,0;3,9;2,8 FWSW N/D N/D OS --- ST 4 N/D VF/AF Brick --- Stream ST N/D HF/AF Gravel --- Stream

9 ST + VF / AF ST + HF / AF monoblock ST + FWSW

10 ST + VF / AF

11 Discharge BOD 5 COD TKN TP TSS TS ph Nº Date m 3 /day mg / L - Inf Rem Inf Rem Inf Rem Inf Rem Inf Rem Inf Rem Inf Feb, % % 3.5 N/D 5.7 N/D 222 N/D 82 N/D Sep, % 24 -% N/D N/D 23 35% 54 2% June, % 74 59% %.4 22% 74 88% % 6.7 Feb, % % % % % % Feb, % % 83 54% 4.6 3% % % Dec, % 279 6% 53 4% % 56 85% 58 37% 7.2 May, % 28 64% 23 35%.8 6% 4 95% 506 6% June, % 49 77% 3 32%.5 64% 53 45% 62 44% % 3 53% N/D % 2 48% 69 8% --- Apr, % % 44 49% % % % Oct, % % 34 4% % 34 47% 7.3 Feb, % 43 5% 5-67% % 557-2% June, % % % N/D 229 9% % Dec, % % 22 23%.9 23% 6 70% 85 37% 7.4 May, % 88 77% 74 34% 7.0 4% 20 86% % Oct, % % 53 72% 3. 58% 72 93% % 7. Mar, % 42 68% 26 5% % 69 88% % Jan, % 32-28%.3-22% N/D 43 23% % 7.0 Feb, % 47 66% 26-5% % 344 9% % 42-29% % 62-85% 60-36% Sep, % 33 70% N/D % 95 80% % 7.3 May, % 84 70% % % % % Mar, % % % % % % %

12 introduction objective methods results conclusions Technology # of systems Removal min; mean; max recurrent problems observed ST + HF/AF 7 ST + VF/AF 2 ST + FWSW 8 COD: 6; 75; 85% (2); TC: <0; <; 2 log (2) COD: -8; 54; 97% (7); TC: <0; <; 5 log (7) COD:59; 73; 85% (3); TC: <0; <; log (3) Clogging of ST and AFs Clogging of ST and AFs; organic overload; Clogging of ST; Clogging of ST; short circuiting in FWSW ST + FWSW + Infil - - UASB + HF/AF Only ST 2 COD: 62% (); TC: < log () COD: -28% (); TC: < log () Organic overload; clogging of AFs Clogging of ST COD: Chemical Oxygen demand; TC: Total coliforms; (N) Number of systems characterised; ST: Septic Tank; AF: Anaerobic Filter; HF: Horizontal Flow; VF: Vertical Flow; FWSW: Free Water Surface Wetland; Infil: Soil Infiltration; UASB: Upflow anaerobic sludge blanket; OUT: Currently out of operation.

13 introduction objective methods results conclusions Some systems present design and construction failures There is organic overload in many systems, mainly due to rapid increase of new connections to the sewerage network The preliminary structures are too small to retain the particulate material during rainfall events Very low and even null biological activity was observed in the majority of the systems in operation due to the erroneous starting up and maintenance of the systems Despite of some organic matter removal, the systems are not eliminating pathogens Many similarities between systems were found, which could suggest the application of design guidelines some decades ago Access roads and fences are urgently needed in many systems Perspectives: pilot scale systems will be implemented soon

14 Thank you for your kind attention Acknowledgements: Empresa Pública Municipal de Telecomunicaciones, Agua Potable, Alcantarillado y Saneamiento de Cuenca, Ecuador