507 cas conventional activated sludge b eaas extended

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Unformatted text preview: ative pond (FP) hours m hÀ1 d 150–300 15–45 6–9 0.5–0.7 CAS – Conventional activated sludge. b EAAS – Extended aeration activated sludge. c AT – Aeration tank. d SC – Secondary clarifier. Source: Adapted from Arceivala (1981), WEF & ASCE (1992), Orhon & Artan (1994), Metcalf & Eddy (2003) and von Sperling & Chernicharo (2005). Table 2 | Operational parameters used to evaluate the WWTP performance Table 3 | Typical monitoring frequency in the 166 WWTP investigated Monitoring frequency Number of WWTP % of WWTP Influent flow range Monitoring index MI Technologies (m3day–1) (samples/year) FP Group 1: ≤217 m3/d; Group 2: .217 m3/d Group 1: ≤2.3; Group 2: .2.3 Twice per week AP þ FP Group 1: ≤549 m3/d; Group 2: .549 m3/d Group 1: ≤3.0; Group 2: .3.0 Weekly Twice per month 10 6.0 AS Group 1: ≤3099 m3/d; Group 2: .3099 m3/d Group 1: ≤25; Group 2: .25 Monthly 13 7.8 Quarterly 15 9.0 Group 1: ≤780 m /d; Group 2: .780 m3/d Group 1: ≤253; Group 2: .25 Once per four months 3 Daily 0 0.0 2 1.2 10 6.0 0 0.0 Undefined 116 69.9 Total UASB 166 100.0 parameters. However, the majority of treatment plants had no clearly identifiable monitoring frequency (undefined) mean concentration higher than that usually reported in and the number of parameters monitored in each WWTP the literature for prevailingly domestic wastewater (Arcei- also varied substantially – from 4 constituents in some treat- vala ; Qasim ; Metcalf & Eddy ; von Sperling ment plants, up to more than 30 parameters in others. & Chernicharo ). The simpler treatment systems, that The number of evaluated systems, the average influent is, ST þ AF, FP and AP þ FP, showed systematically much flow, the mean concentrations of raw and treated waste- higher concentrations for all constituents, except faecal water and the mean removal efficiencies associated with (thermotolerant) coliforms. Possible explanations that the six treatment technologies are presented in Table 4. It could justify the high concentrations of raw wastewater trea- was observed that the influent wastewater presented a ted by these processes could be: unreported industrial 40 S. C. Oliveira & M. von Sperling Table 4 | | Performance of wastewater treatment technologies Journal of Water, Sanitation and Hygiene for Development | 01.1 | 2011 Mean concentrations and mean removal efficiencies, according to the six treatment technologies Technologies ST þ AF AP þ FP FP ASa UASB UASB þ POSTb Parameter Number of WWTP evaluated Average flow (m3 dÀ1) 19 205 73 400 43 1628 13 64,484 10 3038 8 253 BOD Influent (raw) (mg LÀ1) Effluent (treated) (mg LÀ1) Removal efficiency (%) 665 292 59 553 136 75 510 89 82 315 35 85 371 98 72 362 42 88 COD Influent (mg LÀ1) Effluent (mg LÀ1) Removal efficiency (%) 1398 730 51 1187 525 55 1095 309 71 575 92 81 715 251 59 713 141 77 TSS Influent (mg LÀ1) Effluent (mg LÀ1) Removal efficiency (%) 479 165 66 430 216 48 411 153 62 252 57 76 289 85 67 334 51 82 TN c Influent (mg LÀ1) Effluent (mg LÀ1) Removal efficiency (%) 78 61 24 69 38 44 78 45 39 47 22 50 43 48 –13 – – – TP Influent (mg LÀ1) Effluent (mg LÀ1) Removal efficiency (%) 9 7 30 9 4 46...
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