Comparison among the most frequently used systems for wastewater treatment in developing countries

8)

Pergamon

Copynght

PH: S0273-1223(96)OO301-0

Wal. Sci. Tech. Vol. 33, No.3, pp. 59-72.1996. 1996 IAWQ. Pubhshed by ElsevIer Science Ltd Printed In Grea' Britain. AU rights reserved. U273-1223/96 $15'00 + 0·00

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COMPARISON AMONG THE MOST FREQUENTLY USED SYSTEMS FOR WASTEWATER TREATMENT IN DEVELOPING COUNTRIES Marcos von Sperling Department of Sanitary and Environmental Engineering, F~deral Univ~rsity of Minas Gerais. Av. Contorno 842 - 7" andar, 30110-060 Belo Homonte. BraZil

ABSTRACT

The paper presents a series of tables, figures and charts which can be used for the preliminary selection of wastewater treatment systems, specially in developing countries. The systems analysed are: stabilization ponds, activated sludge, trickling filters, anaerobic systems and land disposal. Within each system, the main process variants are covered. A main summary table for quantitative analysis is presented, including easily usable information based on per capita values (USSlcap, W/cap, m2 area/cap, m3 sludge/cap). Other tables for qualitative comparison among systems are also included, one based on a one-to-five-star scoring and the other on a balance between advantages and disadvantages of the main treatment processes. The sludge treatment and disposal is also covered, including a comparative analysis based on a scoring system. Copyright © 1996 IAWQ. Published by Elsevier Science Ltd. KEYWORDS

Appropriate technology, developing countries, process selection, sludge handling, wastewater treatment. INTRODUCfION

Nowadays there is a wide variety of systems which can be applied for wastewater treatment. While in industrialised countries the number of alternatives may be somewhat more limited due to the more stringent efIluent quality standards usually applicable, in developing countries as a whole the breadth of choices to be analysed may be higher. This fact stems from the diversity of effluent standards encountered throughout these countries, ranging from very conservative to very relaxed criteria. Additionally, the cost component and the operational requirements, while important in the industrialised countries, play a much more decisive role in the developing countries. A further aspect in the developing countries is the high contrast usually observable between urban areas - periphery - rural areas. All these points make the preliminary selection of the more appropriate systems for the intended application a critical step, many times overlooked in less careful designs. Figure 1 presents a comparison of important aspects in the selection of wastewater treatment systems, analysed in terms of developed and developing countries. The comparison is forcibly very general, due to the specificity's of each country and the high contrasts usually observable within the developing countries. The items are organised in a decreasing order of importance in the developed countries, according to the author's perception. In these countries, critical items are: efficiency, reliability, sludge disposal aspects and land 59

M. VON SPERLING

60

requirements. In developing countries, these first items are organised in a similar way of decreasing importance, but have a smaller magnitude, compared to developed countries. The major difference lies in what can be considered to be the critical items for developing countries: construction costs, sustainability, simplicity and operational costs. These items are important for developed countries, but cannot be considered to be critical.

IMFOIlTANT ASfIC1S IN lHE SEIiC1ION Of WASlEWAlER 1REAlMENT SmEMS DE\e.QA;O COUNlRlES

EtlWonmentol ~

rnportant

~t

Fig. I. Important aspects in the selection of wastewater treatment systems. A comparison between developed and developing countries. The objective of the paper is to present elements for a preliminary comparison among the systems most frequently used for the secondary treatment of domestic wastewater, with a particular view to developing countries, under tropical or sub-tropical conditions. The items analysed should help the consultant or even members of the organised community to make a first evaluation and preliminary selection of the treatment systems which could present a higher potential applicability for each case under consideration. The information is presented as a series of tables, which make up for most of the paper. TREATMENT SYSTEMS ANALYSED The main systems and the variants analysed are:

• stabilization pond systems (facultative, anaerobic - facultative, facultative aerated, completely mixed aerated· sedimentation)

• • • •

activated sludge systems (conventional, extended aeration, sequencing batch reactors) trickJingjilter systems (low rate, high rate) anaerobic systems (upflow anaerobic sludge blanket reactor, anaerobic filter) /and application systems (slow rate, high rate, subsurface infiltration, overland flow)

Figure 2.a to 2.e presents the flowsheets of the liquid phase (wastewater) of the variants analysed. The list of treatment systems included is by no means exhaustive. Other systems currently applied also deserve a substantial merit. Among those can be mentioned simple natural systems such as constructed wetlands and even more sophisticated compact systems such as rotating biological contaetors and aerated biofilters.

Wastewater treatment in developing countries COMPARISON AMONG THE TREATMENT SYSTEMS

The comparative analysis among the various systems and their variants is presented in a series of tables, described below:

• Quantitative comparison (Table 1). Summary table, including information presented in a simplified way, such as %, US$lp.e., W/p.e., m2 area/p.e., m3 sludge/p.e. etc (p.e. - population equivalents). • Qualitative comparison (Table 2). Comparison on a one-to-five-star system of relevant aspects in the evaluation oftreatment systems, including efficiency, economy, process and environmental problems. • Schematic comparison (Figure 3). Visual comparison, based on bar charts. In the charts, variants of the same system (e.g. the various pond systems) are concentrated in the same bar. The main objective is only a general view ofthe various systems, without taking into consideration the specificities of each variant. • Advantages and disadvantages (Table 3). The analysis is oriented mainly for the comparison of variants from the same system, even though it allows some comparison among different systems. Obviously this type of general approach is forcibly superficial. The intention is not to present values and criteria which cover all the possibilities and local aspects of the various countries. Given their ample regional diversity, there will naturally be designed or operating treatment systems which present distinct characteristics from those covered in the paper. This divergence, instead of representing a conflict, should be faced as an incentive to the widening of the data presented, reinforcing once again the relevance which needs to be attributed to the local conditions. SLUDGE TREATMENT AND DISPOSAL

The analysis of the very important stage of sludge (solid phase) treatment and disposal is also presented as tables, which are described below.

• Sludge processing (Table 4). Sludge handling requirements in the various wastewater treatment systems. • Qualitative comparison (Table 5). Comparison on a one-to-five-star system of relevant aspects in the evaluation oftreatment systems, including efficiency, economy, process and environmental problems. FINAL REMARKS

The overall analysis of the various wastewater treatment processes leads to the conclusion that there is no ideal system applicable to all conditions. Each situation must be analysed individually, with the constant concern of incorporating the local specificities in the stage of investigation and decision. In sewage treatment, the adoption of standard solutions and designs is very difficult. If: on one hand, this could appear as a complicating factor, on the other hand it should be realized that this is one of the aspects which make wastewater treatment so fascinating. Only through the opening of multiple avenues one can really reach an efficient, economical and adequate solution, not only in the design stage, but mainly throughout the operational life ofthe treatment plant (von Sperling, 1994). REFERENCES

ARCEIVALA, S..1. (1981). Wastewater treatment and disposal. Marcel Dekker, New York, 892 pp. METCALF &. EDDY (1991). Wastewater engineering: treatment, disposal and reuse. Metcalf &. Eddy, Inc. 3 rd ed, 1334 pp. PRIOL!, P.S.; NETO, l.A.; NETTO, M.1. (1993). Curvas de custo de esta~lles de tratamento de esgotos para estimativas de investimento. In: J 70 Congresso Brasileiro de Engenharia Sanitaria e Ambiental, Natal·RN, 19-23/09/93, p 641-656 (in Portuguese).

61

M. VON SPERLING

62

QASIM, S. R. (1985). Wastewater treatment plants. Planning, design and operation. Holt, Rinehart & Winston, 726 pp. USEPA - United States Environmental Protection Agency (1979). Environmental pollution control alternatives: municipal wastewater. Technology Transfer, 79 pp. USEPA - United States Environmental Protection Agency (198 I). Process design manualfor land treatment ofmunicipal wastewater. Technology Transfer. USEPA - United States Environmental Protection Agency (1992). Manual. Wastewater treatment/disposal for small communities. Technology Transfer, 110 pp. VIEIRA, S.M.M. (1993). Tratamento de esgotos domesticos em reator UASB. Curso Sistemas de Esgotos. M6dulo ill: Tratamento. COPASA-MG (in Portuguese) VON SPERLING, M. (J 994). Criterios e dados para uma seletrao preliminar de sistemas de tratamento de esgotos. Bio. Engenharia Sanitaria e Ambiental, 3 (1), Jan-Apr 1994, pp. 7-21 (in Portuguese).

WASTE STABIUZAll0N FOND S~1EMS

-.i. •• . .-

•,• •

~

--

---..,.,.

I

FACULTAlN( POND

FACULTAlN( A1iRAlED LAGOON

I Fig. 2.1. F10wsheets ofwaste stabilization pond systems

W1L~tcwater

63

treatment in developing wUniries

ACTlVAlED SLUDGE S'tSTEMS CON\fNl1ONAI. AC1lVAn;D SWDGE

(ConInuoua 'low)

OlClNNli

WA1ER1OCW

·····································fi. .

-

,-

EXlENDED AERAlION (Conltnuouo now)

- -•

+

L

Q.

, SEQUENCING IAlCH REAClORS Ont_ent now)

-• --

Fig. 2.b. Flowsheets of activated sludge systems

M. VON SPERLING

64

lRlCKUNG RLlER SVSlEMS LOW RAlE IlICICIING IlllER

HIGH RAlE 1RIClCUNG IlllER

'"""""'" -"""

Fig. 2.e. Flowsheets oftriekling filter systems

ANAEROBIC SVSlEMS

Pt!rl

UFROW ANAIiROllC SlUDGE IlANKET IlEAC10II

~

--•

-y

~

~ .:=:~

~

y

(~

-

SEI'IC TANK· ANAIiROaIC 11l1ER

-""'"

,-= y

y

~

Fig. 2.d. F10wsheets ofanaerobie systems

W'L~t.:wat.:r

tr.:atm.:nt in d.:vdoping countrks

LAND DISPC>SAL S'iSlEMS LOW·RAtE IN"LIlA1ION

.-y-.

---' -• (CJNodV ~ heme

I~

laa...,.,V*l

IlN'ID INIlLlRAnON

SU8SURfACE INIlLlRA1lON

. r
•-=-'---';'::~L-.-i'I-;.?:;;IiiiiiP.~ ....~

Fig. 2.e. Flowsheets of land disposal systems

65

~

Table I, Typical characteristics ofthe main wastewater treatment systems TREATMENT SYSTEMS

'RELIMINARY TREATMENT PRJM.4RY TREATMENT Ii'ACULTATIVE POND WAEROBIC POND· FACULTATIVE POND iIo'ACULTATIVE AERATED UGOON rrOMPLET.MlXEDAERAT. -SEDIMENT POND. ~NTIONALACTIVATEDSLUOOE

NDED AERATION (CONTINUOUS noW) EOUENCING BATCH REACTOR ~WRATE TRICKliNG FILTER 'HIGH RATE TRlCKUNG F7LTER iUPnow ANAEROBIC SLUOOE BUNKET Is'EPTIC TANK - ANAEROBIC FILTER ~WW JUTE INFILTRATION ~ID lNFILTRATION lvUBSURFACE lNFILTRATION

bJIERUND now

REMOVAL EFFICIENcY

REQUIREMENTS

W.)

BOD

N

0-5 35-40 75 - 85 75-90 75-90 75 -90 85 -93 93 -98 85 -95 85 - 93 80-90 60-80 70·90 94-99 86·98 90- 98 85 - 95

10-25 30·50 30-50 30-50 30-50 30-40 (a) 15 - 30 (a) 30-40(a) 30 -40 (a> 30.40(a\ 10-25 10-25 65-95 10-80 10-40 10·80

~

P ~

10-20 20-60 20-60 20·60 20-60 30-45 (a) 10 - 20 (a) 30-4S(a1 30 -45 (a> 30-45(a\ 10-20 10-20 75 -99 30-99 85-95 20 ·50

COU· FORMS ~

30-40 60-99 60- 99,9 60-96 60-99 60-90 65-90 60-90 60·90 60·90 60-90 60·90 > 99 >99 >99 90->99

LAND

(m 2/1nhab\ <0,001 0,03 -0,05 2,0 - 5,0 1.5 - 3.5 0,25 - 0.5 0,2 -0,5 0,2·0.3 0,25 -0.35 0,2 -0,3 0.5 - 0,7 0,3 -0,45 0.05 -0.10 0,2 -0.4 10· 50 1·6 1·5 1-6

!cONSTRUCT. COSTS (USSIInh.b)

POWER fWllnh.b) ~ ~ ~ ~

1,0· 1.7 1.0- 1,7 1.5·2.8 2,5.4,0 1,5 -4,0 0,2 - 0,6 0,5·1,0 ~

~ ~

~ ~ ~

2-8 20-30 10- 30 10-25 10 -25 10·25 60· 120 40-80 SO - 80 50·90 40-70 20-40 30-80 10·20 5 -IS 5 ·15 5 - 15

References: An:eivala (1981), Metcalf'" Eddy (1991). Prioli etal (1993), Qasim(1985), USEPA (1979.1981,1992), Vieira (1993), von Sperling (1994). infonnatiOll from ochcn and author·. experience

Nota: NA: DOl applicable Enern' requirements do not include the eventual ow -se pumping (a> An additional nutrient removal can be obtained through modifications in the process

TOTAL QUAN11TYOF HYDRAULIC IsLunGE TO B DETENTION HANDLED TIME (days)

-

0,1 -0,5 15 - 30 12-24 3-9 4·9 0.4 -0.6 0,8.1,2 0,4-1,2

NA NA

0.3 -0.5 1,0·2,0

NA NA NA NA

(mJ/lnhab.year)

-

0,6 -1,3

·-

-

1.1·1.5

0,7·1,2 0,7-1,5 0,4.0.6 1,1 -1,5 0,07-0,1 0.07-0,1

·-

·

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<:

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Wastewater treatment in developing countries

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67

M. VON SPERLING

68

COMPARISON AMONG THE TREATMENT SYSTEMS EFFICIENCY E"ICIENCY IN coa.WOltIlil NrMOVAL 1"1

InICIENCY iii 8:)0 "IEMO't'Al ('J.)

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E

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COSTS CONI'ftUCTtON COITIIUSSihab)

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100

69

Wastewater treatment in developing countries

Table 3. Advantajtes and di5ldvanlajte5

WASTE STABIUZATION POND SYSTEMS ADVANTA<:ES

SYSTEM

FACULTATIVE POND

ANAEROBIC POND· FACULTAT1VE POND

FACULTAT1VE AERATEDUGOON

COMPlETELY UIXEDAERATED UGOON. SEDJUENTATJON UGOON

• SalWo<:Iary dfociency ..

BOD '""""'" • Eftieienl in p&Ihop rwnoval • Simpl<~--"""ond.....-..... • Low 0llIIIlnIc:lica ond - - " " " _ • No IIlOChanicaI oquipmenll • AImoIt no enercY nquiranen&a • SoWfo<:lary _ to Iood varialiono • Siudoe mnoval ......icallv ... neceosIIV • Same .......IlaIi....... • I...owa' land nquircmcnb cornpare4 10 sinal_ fM:uh.l&iw

.....

• RcIati..I Y l i m p l e _ - - u o a a n d _ • l.owa' Iond roqu_ cornpare4lO ......1laIi....... and _ i..fllCUllaIi....... • Orcalcr indcpendcnco &am oIimalic condllionl cornpare4 to .................. and ...-obio-fllCU............ • Sliahtly 1....« effice-=y in BOD nrrICJWl cornpare4 to fllCUllaIlVO ..... • Saliafadol')' resastanee to load variallOlll • Low llOIIibolitv of odour oroblems • Same .. fllCUllaIlVO MraIed ........ • l.owa' Iond roquiremcnls compondlo all pond iyUlM

ond ndialion)

• P_ibl< ..... . • Same ....................

• Pc.ibII odour ... iancI in .-.obic paM • ......... DOOdol~in&linoIoftI_.. _ " ' _

• Jlrr-.::e .lqUlpmenl • 5h.............. tophiolic:olioa ..... • Lond nquu.n- iblllU",

• Rdali..ly"'... onercYroqu......

......-)

• Same ........ lIoIivo _ _ ........ (_Iond

• FOIl filli.Soldle~ _ _ with lIu.... (2 10 , yo.o)

• Need or _i""out or periodic (2 10 , yean)llud8<_1

ACTIVATED SLlIDGE SYSTEMS ADVA'ITAGES

DISADVANTAGES

• Hlp, cffiatney 11'I BOD removal

•

• ro.ibilit)' of'biolopl N • P removal

• Hi'" -sr--.pllOll • Nood 01 oop/uolicoIod - ' ' " ' • Hip mochInisalioo .....

• NilriJicaliOll ....lly adUcvod (tropical-.lrioo) • 0pcn&MJn0l fleXlbihty

rct1ft"""orujlow)

• Opcn&MJnol_licily .... brin& ""lloot"_ • r-ibieDOOdIO_al..... oIII_to-.ply_ 1Uinpnl• Pod......... dependenl,", oIimo1ic~~

adoun

• Low land reqUlfementl

EXTENDED AERATION

DiSADVANTAGES

• HI...... r-qu...... • DdflCUhy in -.pi...... with IUinpnl eIII_ _

• Noodolilorgedi_toneuby""'-

SYSTEM

CONVENTIONAL ACTIYATEDSLUDGE r.....-jIow)

or the main wastewater treatment systems

• Reliable, provided llIlOUp IUporviIion is ai• Low DOSJibilities of odours. insects and worms • Same u oonvenhonallClivaaed sludac • SyNm wrth htgher efficiency io BOD mnovaI

• ConIisIent mtnficalion • Simp'- 1IIan COll-...OllaI ....voted lIudp • t- t1udae produced c:omparod 10 COllvenlional .......... oJud.. • Slucfce ••bdizabOft in 1he rac:&or itMlf (.,.,..ae di. . . . DOl

Hlp CDnIInIe:tIOII and operation com

• Relaaiwl)' -.itt", 10 IoXic bldI

• Nood oloomp.... 11""'""",- ond diapoul • P-ib.. environmcnlal oroblems wilh ooisa and ...-1 • H,p _ a n d - - " " , , _ • 5)'1lel1l ...IhIU.... -zr ...............

• Hip mochInisalioo IovaI (aIIhou'" r - ..... ---.... ....voted lIudp) • Notdoltl.d.. _anddiapoul(al"-p ....l _

• "'-r)

--r)

• Hip Na.unc:e &0 variabc:n an load and 10 toxic:: IOIdI • SattJfactorv indmendence fioom cltmalic eondftlON

SEQUENCJN(J BATCH REACTORS (I""",,llNrrtjlow)

• HI'" lIffiClency UI BOD removal • SalWo<:Iary N and _ibly P mnovaI • Low lond roquirtmonla • 5impl.. _

.... '"""' ...._

II""" iyUlM

• t- oqui..,- _ die oIhor ...._ lIud.. iyUlM • OponIiOllal nexibility (variOliOll of eye"') • Secondarv _I., and recycle PU"'f'lIlOC - . r y

w"'u.d _ _

ar--

• Hip OOftIINdJcm and openbOIl COllI • Hi.... oIhor ...._ 1I..... • ---""or Nood 01 lIudp _ __l and diapoul (varitble wilh _

• UouaIIy .............. i1i.. for Il'IIaIlor popu~

M. VON SPERLING

70

SYSTEM WWRATE

T7l1CXlJHG FlLTER

HIGH RATE

T7l1CXlJHG F1LTER

Ifo_.

• H'....

• c:ono-

TRICKUI\IG fILTER SYSTEMS DISADVAI\ITACE.~ ADVAI'ITACES • I.-~ lIc"JI'd..,._ ....'*'
nilnfocation (Irop>caI .........)

• LAnd rcquit_ rcla1ovcly ...11

• Hi.... 1aIld rcqu~ -.pamI1O h;p .... fo.....

• • • •

• Ic1aliwlyleNitiwlolDDc'" • N.... .tllud... . - and di....-J (aIIllou"'llIbilizallco.

• ldaliw cIcpaIdon
S~ Ih...."i'*'
.....

loIed>uliso1ion IcwI rcIlliwly ....1 S....1c 1DOdluucaI ....; _ SIude< IlabIhzalion .. IN fill. . . .1f

•

Goodelf~

,..filkn)

.. BOO""""(_p _

..... Iow

• lAw IaIld rcquw-

• SOnplw"" Kti...... oNdp

• H;.... lIcxibililylhcnlow .... fohcn • H;.... _lOloodvuialionc_low_rdlen • Lowoossibtlit.ea afodoun

• Reuonable.tliaeney '" 800 removal • Very low lend rcqu.......... • Low oonstrudKln and operation ClOlIU • L.ow IftCIl:.Y COI1IUmplIOII

• No padc.1I'I1 media

• Sunplc ClanIlI'uClioa. cpenlion ud malnIenInCI • Verycmalillud&.~. • Sludge -.bihzallM ~ Iht tudor ilIc:lt • Sludp hondbn& rcquno ooIy oIi....-J

ANAEROBIC F1LTER

• 0pcnI00n 1l1....1y ...... ~_Iow.... fihcn • HI.~oc.u • acloliwclcpaldon
• Ncodoi_...... . . . , . . _ ............ • H;............

AI\IAEROBIC SYSTEMS ADVAI'ITAGES

SYSTEM

UPFWW ANAEROBIC SLUDGE BUNKEr REACTOR

-"')

• •.-ibIc probIcmo wilh nioo • H;oh_'"

-

• Fast ratart after "1'I'T\IIXe.t OMntion • s.mc .. _pIlow ........... Ilud&cblank.(....,_oi pocIun& _a) • Good......-lOdtlfmnllypoc .... - . . . . . . o t • 000cS rai:Itancc &0 vanIliona illoM

DISADVAI'ITACES

• DtffiQlhy .. oompl)'ll'l wIIh • .£f/1ucnl"",

1Inn,- effluent . . . . .

_ i..llyplcuant

• u.-wcdafyN a ' ........ • ....bihty 01 cxIoun • Slow pr~ lIIft....p • Relalivcly""";", 10 Iood vcriIlionI • May NqUiri poIl-tn:almcnl

f

, • Ildf.... ky .. """'l'lYon& WI\h IOn".... _ _

• Eftlucnl ... _ocaJly pleuull

• Uaoauclcdafy Na , ........ • ....bilityoi....... • Ricka 01 cIouin& • Hi... _ o t - . - . . w ...idI ...... aIII_ • RlWiclaollO _ _ oronn..... wilh low _ _ ool... COftClentr1It<...

SYSTEM $WWRATE

1NF1LT1lATTON

_on.--"""

• 1Aw~.-dopentioaWIII

• Good IWIIIUClIIO VIriationI in IoId • No ....... I0 ... _

• Soil far\ilica1icoa .... _itioninl

•

'~oi

_ _ ""&Ilionoi..,;...llwral_

• Oroundw_ rccharp

RAPID lNFlLT1lATTON

SUBSURFACE 1NF1LT1lATJON

OVElUANDFWW

-

LAND DISPOSAL SYSTEMS DISADVAI'ITAGES ADVANTAGES • Veryblpluld ......_ _ • Vry Au"'" afflCMnCY 1ft BOD and oohfonn nmovaI • ._bdotyot......... • SIlicCaonodO*hod .... _endfonaJdJIJlCIUI • RclaIJvcly dcpcndcftt. _ and IlUlricot rcqu_ • Somplo end....m.-

• s.mc .. Ilow .... w.iVI&,. (a/Ihoup cffiacncy .. po1hoccn ramoval ic 1_) I..-Iend roqul_ -.pared 10 .Iow .... inIi\lralion l A w " ' " OIl .-.t 1l0p0 """"...'on""""u.;..1ho ..... SIInt u rapid infihralion wilh ~ linoo • No ...... ,.....I.... • • • •

.........

• Dependenl on toil c:hIndInItia

• ot_Uodappl_ a.- ot-....incboft 01""""" 10"''''''''''' in .... • .....,.liIy 01................ or ap;e..hurol_.. (willi -y)

• '-,bili'y 01 dlcnu<:aJ elf_ on coil. vcplabl
-

· ,..oblc_

u rapid •• Same Ncodor_ _uJiltrlllon _ lOoJ_ _ oiappl_(_

• Abow.-.t- ....... _ .. pub

• w&Cf 1yIlaIM'-......-bIe coile 10 ............

• N o " ' " OIl climalic _ _ • No";"'lcmowilhWftUhl.end_.. -...inalion • s.mc. rapt4 inIi\lralion (bul- ~ oIroul ~"'wilh . . . . . ... .c . OIlo ..............1 . I_ _ _hi. .......il_(_ 1hc ...... di_r....;",,\

Uld_)

.....

a _

am-.c.--_.. . . .

.. rapt4on1i_

• 0n0Iar cIcpaIdon
• OonanI_oir...

71

Wastewater treatment in developing countries

Table 4. Siudee handline in the main wastewater treatment systems WASTEWATER TREATMENT SYSTEMS

'RlMAIly TREAnfEIVT "ACULTATlVE POND iJ.NAEROBIC POND - FACULTATIVE POND fACULTATIVE AERATED LAGOON OMPlEr. MIXED AERAT. - SED/MEIVT. POND. ONVENTIONAL ACTIVATED SLUCXJE /ixTENDED AERATION (COIVTINVOUS FLOW) EOUENClNG BATCH REACTOR /-OW RATE TR/CXUNG F7LTER IGH RATE TRICKLING F7LTER JPFLOW ANAEROBIC SLUCXJE BLANKET EPTIC TANK • ANAEROBIC F7LTER WW RATE INFILTRATION WID 1NF1LTRAT/ON UBSURFACE INF7LTRAT/ON OVERLAND FLOW

USUAL SLUDGE IlANDUNG DIGESTION DEWATERING

REMOVAL FRWUENCY

THICKENING

variable ea > 20 yean >20 yean - 10 yean < S yean - continuous

x

x

x

x

•

•x

- continuous

- continuous - continuous - continuous variable variable

-

x

x x x

•

FINAL DISPOSAL

x

x

x x x x

•x

x x x

x x

(a) Removal some times per day in conventional prinwy settlen and once every 6-12 months in ""Ptic tanks

x

....

'"

Table 5. Relative comparison amone the sludge treatment systems \II
OrDATIOI'lI r1tOCUS

RJOUCT1ON DnCIDICY

SLUDGE

VOLVNI

ORGANIC MATTlJIIN

1C0llOMYIN RIQIJIRDID/TS

lAND

I

ENERGY CONSTRUC noN

06101

RnlsTANClCAl'ACITY

nnw

VARIATIONS

INTWENT

QUAUTY

QIlA. BlUTY

IIMPU· CITY

I

INDlI'lN. , LOWER OUICION roSSIBI·

CLlMATit

UTY OF

ODOURS

TOXICS

VAlUATIONS

Gravity

++

0

+++

.+••

+......

.... ++

+++

++++

++++

++++

++-++

.. +

++

F1<>fotiOlt

++

0

+++

+++

+++

++

+++

++++

++++

++++

++

+++++

+++++

SLUDGE nuCXEHlNG

ECONOMY IN COSTS

Mecltoltk:ol

+++

0

++++

++

+++

++

+++

+++.

•• ++

++++

+++

+++++

... ++

'ABIUZATJON

I

A_Ie

+

++••

++

+

+H

++

++••

++++

++

++++

+++

+++

.-+.. ++

AnMroo/e

+

++~

++

++++

++

++++

+++

+++

++

++++

++

++

+++

WATERING

I

DryI"I bods Shtdg. kgOOfts Mecltolfical

! CI>

0

I

+++

I

""H/+-++...

0 0

Nolc: .... 1C
~

<: 0 Z

+: last favourable

++++, +++. ++: intermediate, in decreasing order

0: null effect

+ I +++++: variable with the process. equipment or desien