7/30/2019 is.2470.2.1985.pdf

1/24

Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to

information for citizens to secure access to information under the control of public authorities,in order to promote transparency and accountability in the working of every public authority,

and whereas the attached publication of the Bureau of Indian Standards is of particular interest

to the public, particularly disadvantaged communities and those engaged in the pursuit of

education and knowledge, the attached public safety standard is made available to promote the

timely dissemination of this information in an accurate manner to the public.

! $ ' +-Satyanarayan Gangaram Pitroda

Invent a New India Using Knowledge

01 ' 5 Jawaharlal Nehru

Step Out From the Old to the New

1+, 1+Mazdoor Kisan Shakti Sangathan

The Right to Information, The Right to Live

! > 0 B BharthariNtiatakam

Knowledge is such a treasure which cannot be stolen

IS 2470 (Part 2) (1985, Reaffirmed 2001): Code of Practice

for Installation of Septic Tanks, Part 2: Secondary

Treatment and Disposal of Septic Tank Effluent (Second

Revision). UDC 628.352 : 006.76

7/30/2019 is.2470.2.1985.pdf

2/24

7/30/2019 is.2470.2.1985.pdf

3/24

Gr6

IS: 2470 ( Part 2) - 1985( Reaffirmed 2001 )

Indian StandardCODE OF PRACTICE FOR

INSTALLATION OF SEPTIC TANKSPART 2 SECONDARY TREATMENT AND DISPOSAL

OF SEPTIC TANK EFFLUENT( Second Revision)Second Reprint JANUARY 2003

UDC 628.352: 006.76

Copyright 1985BUREAU O F INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NE W DELHI 110002

December 1985

7/30/2019 is.2470.2.1985.pdf

4/24

IS : 2470 (Par t 2) 1985Indian Standard

CODE OF PRACTICE FORINSTALLATION OF SEPTIC TANKS

PART 2 SECONDARY TREATMENT AND DISPOSALOF SEPTIC TANK EFFLUENT

( Second Revision )Water Supply and Sanitation Sectional Committee, BDC 24

RepresentinghairmanSHm J. D' CRUZ "Vater Supply & Sewage Disposal Undertaking,New Delhi

MemblrsCHIEF E ~ G I N E E R ( CIVIL I ) (Alternate toShri J. D' Cruz)ADVISER ( PHE) Ministry of Works and HousingDEPUTY ADVISER ( PHE) (Alternate)SHRI M. S. ASNA:s"I . Public Works Department, Delhi Administration,. New Delhi ..SHRI P. C. SRIVASTAVA (Alternate) .SHRI N. S. BHAIRAVAN Public Health Engineering Department, Govern.ment of Keraia, TrivandrumSUPERINTENDING ENGINEER ( Attemate )SHIn I. CHANDRA Public Works Department (Public HealthBranch) Government of Haryana,ChandigarhSHRI K. K. GANDHI ( Altlrnate)CHIEF ENGINEER (CONSTRUCTION) Uttar PradeshJal Nigam, LucknowSUPERINTENDING ENGINEER (Alternate) .SHRI R. C. P. CHAUDHARY Engineers India Ltd, New Delhi .SHBI H. V. RAO (Alternate)SHRI S. K. DASGUPTA Calcutta Metropolitan Development Atlthority,. CalcuttaSHItI S. R. MUKHERJEE (Alternate) . .PROP J. M. J ) AVE Institution of Engineer. (India), CalcuttaSRKI S. G. DEOLALIKAR In personal capacity (Flat No. 1.03, S a ~ i t r i CinemaCommtrcial Complex, Greater Kailash II, NewDelhi)

( Continued on page 2 )~ Copyright 1985

BUREAU OF INDIAN STANDARDSThia publication is protected under the .Indian Copyright Act (XlV of 1957) andreproduction in whole or in part by any means except with written permission of thepublisher shall be deemed to be an infringement of copyright under the said Act..

7/30/2019 is.2470.2.1985.pdf

5/24

IS : 2470 (Par t 2 ) - 1985( Continued from page 1 )

.'vIembtrsHYDRAULIC ENGINEER

CllIEF ENGINEER (SEWERAGEPROJEC'J:S ) (Alternate)SHRI R. A. KHAN::S-ASBl t I D. K. MITRA (Alternate I )SIIRI1. S. BAWF:JA (Alternate II )

RepresentingMunicipal Corporation ofBombay Greater Bombay,

Public Health Engineering Departnwllt,Government of Madhya Pradesh; BhopalSHU! P. K I ~ l s n A N A N Central Public Works Drpartmcnt, New DelhiSURVEYOR OF WORKS-I ( NDZ)( Alternate)SHBI S. R. KSIURFlAG.\R National Environmental Engineering ResearchInstitute ( CSIR ), NagpurDR P.V.R.C. P ' \ > i r C K j ~ R (Alternate)SHRl M. Y. MADAN The Hindustan Construction Co Ltd, BqmbaySHRI C. E. S. RAO (Alternate)SHRI S. L. MAINIMA:-:rAGlNG DmF:cToR

Punjab Public Works Department (Public HealthBranch), Government of Punjab, PatialaPunjab Water Supply & Sewerage Board,ChandigarhSHB! R. NATAHAJ AN Hindustan Dorr-Oliver Ltd, Bombay. SHRI SUBHASH VER)tA ( Alternate)SHRI K.J. NATR All India Institute of Hygiene & Public Health,SHHI D. GUIN (Alternate)SHRl A. P o : - : r N A ~ m A L A ~ 1

SHBI RANJIT SINGHDB A. V. R. RAOSHRI O. P. RATBA (Alternate)PROF Y. N. R A ~ A C R A N D B A RAOM u B. S. PARMAR (Alternate)SECRETARYSECRETAByGENERAL

CalcuttaTamil Nadu Water Supply & Drainage, Board,MadrasMinistry of RailwaysNational Buildings Organization, New DdhiEngineer-in-Chief's Branch tMirtistry of Defence ),New DelhiIndian Water Works Association, BombayInstitution of Public Health Engineers India,CalcuttaSHRl R. N. BANERJEE (Alternate)SHBI L. R. SEHGAL L. R. Sehgal & Co, New Delhi .SHBI S. K. SHABMA Central Building Research Institute (CSIR),RoorkeeSHRI B. N. THYAGABAJA Bangalore Water Supply & Sewerage Board,BangaloreSHRI H. S. PUTTAKEUPANNA (Alternate)SHBI V. VARADARAJAN Madras Metropolitan Water Supply & Sewerage

SHBI S. DAIVAMANI (Alternate) Board, MadrasSHBI G. RAMAN, Director General, lSI (Ex-officio Member)Director ( Civ Engg )Semtary

SHBI A. K. AVASTHYAssistant Director ( Civ Engg ), lS I

2( Continued on page 21 )

7/30/2019 is.2470.2.1985.pdf

6/24

IS : 2470 ( Paaot 2 ) - 198$Indian Standard

CODE OF PRACTICE FORINSTALLATION OF SEPTIC TANKSPART 2 SECONDARY TREATMENT AND DISPOSALOF SEPTIC TANK EFFLUENT

( Second Revision)o. FOR E W 0 R D

0.1 This Indian Standard ( Part 2) (Second Revision) was adopted bythe Indian Standards Institution on 28 February 1985, after the draftfinalized by the Water Supply and Sanitation Sectional Committee hadbeen approved by the Civil Engineering Divisicm Council.0.2 In a septic tank, even if of adequate design and capacity, only aportion of the suspended solids settle il'l the tank, the dissolved organicmatter and some of the suspended matter are discharged from the tankin the effluent and will cause a health hazard if the effluent is notadequately d!sposed of.0.3 The title .of the code which w a ~ orig.inally 'Code ofpractice for designand construction of septic tank: Part 1 Small installations, and Part 2Large installations', have also been amended to read 'Cocie of practicefor installation of septic tanks: Part 2 Secondary treatment and disposalof septic tank effluent'.0.4 This standard covers the recommended practice for the disposal ofeffluent from septic tanks only. The design and constrtlction of small aswell as large septic tanks (up to 300 persons) have been covered ihIS : 2470 (Part 1) 'Code of practice for installation of septic tank: Part 1Design criteria and construction'.0.5 Disposal of effluent from septic tank was originally given in IS : 2470(Part 1 )-1968 'Code of practice for design and . construction of septictanks: Part 1 Small installations (f irst relJisi(Jn)'. In this revision. thedisposal of septic tank effluent by biological filter have been covered indetails. Upftow anaerobic filters for the disposal of effluent from theseptic t a n ~ , which are preferred in rocky areas, are also covered indetail. .

3

7/30/2019 is.2470.2.1985.pdf

7/24

IS :2470 ( Par t 2 ) 19850.6 For the purpose of deciding whether a particular requirement ofthis standard is complied with, the final value, observed or -calculated,expressing the result of a test, shall be rounded off in accordance withIS : 2-1960 *. The number of significant places retained in the roundedoff value should be the same as that of the specified value in thisstandard.0.7 This Code of practice represents a standard of good practice andtherefore takes the form of recommendation.

1. SCOPE1.1 This code lays down recommendations for the methods of treatmentand disposal of effiuent from septic tanks.2. TERMINOLOGY2.0 For the purpose of this standard, the following definitions shall apply.2.1 -Biological Filter -:.... I t consists of a bed of gravel, broken stone,clinkers or such other material through which sewage flows. Theorganic matter present in the sewage gets partly removed and stabilizedby the biological slime on the surface of the media.2.2 Dispersion Trench - A -trench in which open jointed pipes arelaid and surrounded by coarse aggregate media and overlaid by fineaggregate. The effluent gets dispersed through the open joints and isabsorbed in the neighbouring soil.2.3 EfBuents

a) Tank Eifluent - The supernatant liquid discharge from a septictank. -b) Filter Eifluent - The liquid discharged from a biological filter.

2.4 Filter Media ---- Materials, such as clinker, broken stone and gravelthrough which sew-age flows and on the surface of which zoological filmsdevelop.2.5 Seepage Fit (Soakaway, Soak Pit) - A pit through whicheffluent is allowed to seep or leach into the surrounding soil.2.6 Sewage - The liquid waste of a household ot community includinghuman excreta. -

"Rules for rounding off numerical values ( revised).4

7/30/2019 is.2470.2.1985.pdf

8/24

IS : 2470 ( Par t 2) - 19852.7 Subsoil Water - Water occuring naturally below the surface ofthe ground.2.8 Surface Water - The run-off from precipitation and other waterthat flows over surface of the ground.3. PRELIMINARY DATAtFOR DESIGN3.1 In order to design secondary treatment works of the treatment ofeffluent from septic tanks, information on the following items should becollected.

a) Nature of soil and subsoil condition1) The fullest possible i n f ~ r m a t i o n on the nature of the soil andsubsoil conditions should be obtained, as weIlj as theapproximate water table and any available records of fioodlevels or information as to the variation, seasonal or otherwise,in the water table.2) The soil should be explored to a suff;cient depth to ascertainthe soils horizons and the soil types, grading, structure andpermeability. The external drainage factors, such as slopeof ground and position of surface water drains, if any, should

be ascertained. Exploration of the soil to a significant depthshould be made because casual or visual inspection may failto reveal unsuitable conditions, such as an impervious granitelayer under. sand, or on the other hand suitable conditions,such as permeable schist overlaid by clay.3) Soil Types - An approximate field identification of the soilsshould be made in accordance with the methods given inIS: 1498-1970*. Trial bores or boreholes should be sunk

along the line of the proposed filter and data there fromtabulated. In general, the information obtained from trialbores is more reliable than that from boreholes. Thepositions of trial bores or boreholes should be shown on theplans together with sections showing the strata found and thedates on which the water levels were recorded. Fullinformation should be given as to the structure, type, colour,permeability, depth and horizons of the soil, as well as anyimpedances to drainage such as rock bars.Classification and identification of soils for general engineeri1;lg .purpasl1 .,(jirstrevision ).

5

7/30/2019 is.2470.2.1985.pdf

9/24

IS : 2470 (Par t 2 ) - 1985-1) Percolation Test -- To decide on the details of a soil absorptionsystem a soil absorption test as given in Appendix A shallbe conducted. The percolation rate, that is time requiredin minutes for water to fall 25 mm in the test-hole shall be

determined. A test in trial pits at more than one place inthe area should be undertaken to permit deriving an averagefigure for percolation rate.b) Site plan showing the proposed or existing buildings as well asreduced ground levels over the site.c) Discharge from the septic tank.d) The position and nature of outfall ditches, wells, tanks or smallstreams in the vicinity, if any.

3.2 When assessing the feasibility of a proposed effluent disposal schemeinvolving absorption of effiuent in soil, consideration should be given tofactors such as:a) The area of land available for the absorption.b) The risk of prejudicing adjoining property, underground watersupplies, swimming and wading pools and the like, by seepagefrom the area.c) The permeability and depth of the soil on the proposed site forthe absorption area. Percolation tests are useful but the seasonof the year when the tests -are made and many other factorshave to be taken into account when assessing the results of thetests. Long-term efficiency of an absorption area can beadversely affected by high concentrations of chlorides andsulphides in the soil.d) Any seasonal changes in ground water level and absorptivecapacity, of the site.e) The climate and its effect on the evaporation from the site, forexample, distribution of rainfall, hours of sunshine, prevelanceof wind.f) The effect of seepage and surface water from surrounding areasat higher levels than the proposed absorption area.

3.3 Before any work is started, the approval from the AdministrativeAuthority should be obtained.6

7/30/2019 is.2470.2.1985.pdf

10/24

IS : 2470 ( Part 2) Q 19854. METHODS OF TREATMENT AND DISPOSAL OF EFFLUENT4.1 The following methods of disposal are described in this Code:

a) Soil absorption system,b) Biological filters, andc) Upflow anaerobic filters

4.2 Depending on the position of the subsoil water level, soil and subsoilconditions, the recommended method of disposal of the effluent is givenin Table 1.TABLE 1 RECOMMENDED METHOD OF DISPOSAL

FOR SEPTIC TANK EFFLUENT

POSITION'OF THESUBSOIL W A T E R

LEVEL FROMGROUND LEVEL

Within l'S m

Below I'S m

( Clauses 4,2, 6,0 and 7,0 )SOIL AN D SUBSOIL CONDI1.'lON

r - - - - - - - - . , - - - , . - . - - - - . A . . - - - - ~ - - - - - - - - - ~Porous Soil wi th Percolation Rate Dense and clays soil, -_______ A..________ , . .- - , with percolation rateNot exceeding Exceeding 30 min exceeding 60 min

SO min but not exceeding 60 minDispersion trenchlocated partly orfully aboveground level ina mound

Seepage pit ordispersion trench

Dispersion trenchlocated partly orf u l l v a b o v eground level ina mound

Dispersion trench

Biological filter partlyor fully above groundlevel with under-drainsor upflow anaerobicfilter and the effluentled into a surface drainor used for gardening

Subsurface biologicalfilter with underdrains or upflowanaerobic filter andthe effluent led into adrain or used forgardeningNOTE - Where the above mentioned methods are not feasible an d where theeffluent has to be discharged into open drain it should be disinfected,

5. SOIL ABSORPT ION SYSTEMS5.1 Design of Soil Absorption Systems-The ' allowable rate ofapplication of effluent per unit area of dispersion trench or seepage pit islimited by the percolation rate of the soil (determined in accordance

7

7/30/2019 is.2470.2.1985.pdf

11/24

IS : 2470 (Par t 2 ) - 1985with Appendix A) and the values obtainable from the gl'aph given inFig. 1 may be used for guidance; the allowable rate of effluentapplication for certain selected values of percolation rates are given inTable 2.

'I !I, I

oo

I I

Ii\I \'I ,I

II ! I ! ! 11 I I I II !! II !\ I II I III: I! Ii I I I ' "HI"I Ii l t t r l ~ "I II I: I ' ! i I , . I II ~ ~ L ~ i ~" I !..........

..... ... I !

: I10 20 30 40 50 60 70

S1ANDARD PERCOLATION RATE, MINUTES ( t)Q = 204, J t

FIG. 1 ALLOWABLE RATE OF EFFLUENT ApPLICATION FORSTANDARD PERCOLATION RATE

5.2 Construction of the Soil Absorption System. - Two types ofsoil absorption system have been covered:a) Seepage pit, andb) Dispersion trench.

5.2.1 Seepage Pit - The seepage pit may be of any suitable shape withthe least cross-sectional dimension of 0'90 m and not less than 1'0 m indepth below the invert level of the inlet pipe. The pit may be linedwith stone, brick or concrete blocks with dry open joints which shouldbe backed with at least 75 mm of clean coarse aggregate (see Fig .2A).The lining above the inlet level should be finished with mortar.. In thecase of pits of large dimensions, the top portion may be narrowed to8

7/30/2019 is.2470.2.1985.pdf

12/24

i s : 2470 ( Par t 2) - 1985reduce the size of the RCC cover slabs. Where no lining is used, specially,near trees, the entire pit should be filled with loose stones. A masonryring may be constructed at the top of the pi t to prevent damage byflooding of the pit by surface run-off (see Fig. 2B). The inlet pipe maybe taken down to a depth of 0'90 m from the top as an anti-mosquitemeasure. Illustrations of typical constructions of seepage pit are givenin Fig. 2

TABLE 2 ALLOWABLE RATE OF EFFLUENT APPLICATIONS TOSOIL ABSORPTION SYSTEM

P E l ~ C O r , A 1 ' I O N RA'l 'F.Min

1 or less23451015304560

( Clause 5.1 )MAXIMUM RATE or"

EJo'FLUENT ApPLICATIONl/m"/day204143118102906552373326

NOTE 1 - The absorption area for a dispersion trench is th e trench bottom area.N O T E 2 - Th e absorption area for seepage pits is the effective side wall area,effective depth being measured from 150 mm below invert level of inlet pipe to thebottom of the pit ( see-Fig. 2).N O T E 3 - I f the percolation rate exceeds 30 minutes, th e soil is unsuitable forsoakaways. I f the percolation rate exceeds 60 minutes, the soil is unsuitable for an ysoil absorption system.

5.2.2 Dispersion Trench - Dispersion trenches shall be 0'5 to 1'0 m deepand 0'3 to 1'0 m wide excavated to a slight gradient and shall beprovided with 150 to 250 mm of washed gravel or crushed stones. Openjointed pipes placed inside the trench shall be made of unglazedearthen-ware clay or concrete and shall have minimum internaldiameter of 75 to 100 mm. Each dispersion trench should not be longerthan 30 m and trenches should not be placed closer than 2'0 m.9

7/30/2019 is.2470.2.1985.pdf

13/24

IS : 2470 (Par t 2 ) -1985

1\ f ~ ::r .!: 0:l5E w '

C.:: N1NG ". ' ' 00" . ' t.. ' , 45,crn

C-t.M"NT < ,;, ~ . " i GLgO ~LASTER '"

BRICK, STONE' ORCONe B L O C ~ LINING.WiTH DRV ,;(',;NT5

u >o i=L l ~ _ ~ ~ 75 ern THiCK MINOUTER CASINGWITH COARSEA G G R ~ Gt.T E 52A EMPTY PIT WITH l.INlt.JG

28 PIT WITH FILLING WITHOUT LININGFIG.2 TYPICAL ILLUSTRATIONS OF SEEPAGE PITS

10'

7/30/2019 is.2470.2.1985.pdf

14/24

I , IS ; 2470 ( Par t 2 ) - 19855.2.2.1 The covering for the pipes on the top should be with coarseaggregate of uniform size to a depth of approximately 150 mm. Theaggregate above this level may be graded with aggregate 12 to J5 mmto prevent ingress of top soil while the free flow of water is in a way

retarded. The trench may be covered with about 300 mm of ordinarysoil to form a mound and turfed over. Dispersion trenches are notrecommended in areas where fibrous roots of trees or vegetation are likelyto penetrate the system and cause blockages. The finished top surfacemay be kept at least 150 mm a'ool:e ground level to prevent directflooding of the trench during rains. Illustration of a typical soilabsorption system through dispersion trenches is given in Fig. 3.5.3 Location of Subsurface Absorption System - A subsoildispersion system spall not be closer than 18 m from any source ofdrinking water, such as well, to mitigate the possibility of bacterialpollution of water supply. I t shall also be as far removed from thenearest habitable building as economically feasible but not closer than6 m, to avoid damage to the structures. The actual distance, however,shall be based on the solI conditions in. relation to both percolation andbearing capacity. Care should be taken that the ground below theadjacent building is not likely to be affected by the effluent seeping intothe soil. In lime stones or crevice rock formations, the soil absorptionsystem is not recommended as there may be channels in the formationwhich may carry contamination over a long distance, in such case, andgenerally where suitable conditions do not exist for adoption of soilabsorption systems, the effluent, where feasible should be treated in abiological filter or upflow anaerobic filters.

5.3.1 It is an advantage if the area. available for disposal of effiuentis large enough to permit relocation of absorption trenches whenreplacement of trenches becem e ne.cessary.6. BIOLOGICAL FILTERS6.0 Biological filters are suitable for treatment of septic tank efHuentwhere the soil is relatively impervious (see Table I ), water logged areasor where limited land area is available. In a biological filter, theeffluent from septic tank is brought into contact with a suitable medium,the surfaces of which become coated with an organic film. The filmassimilates and oxidizes much of the polluting matter through theagency of -micro-oganisms. The biological filter requires ampleventilation and an efficient system of underdrains leading to an outlet.6.1 Construction - The depth of medium should be 1400 mm butnever less than 900 mm. The medium should be retained in positionby walls of adequate trench. The filter should have a concrete floor,

11

7/30/2019 is.2470.2.1985.pdf

15/24

to

IOOmm'* PIPEFROMSEPTIC TANI>--.

_L ._.-Y-'C ~ - - " -# c= - = : : L - i ~. ' lOmNAX-DETAIL ATOPEN JOINT

TO 100 mm (J UNGLAZEDE A R T ~ E N W A R E PIPES

30cm

DISPERSION TReNCH ~ l ~ ~ D TURFEDORDINJ.RY OOll

't , ~ l : , t ~ 4 t : ; . ~ r "4 ~ ' } ' ' : : ' Y ; ' - f . , . ' 1 ' r ' ~ ' ' ' lL..8mMIN

\

, ~ ~ ~ : ~ { g : * ~ ~ j : iWELL G R A O E o - - I I i % ~ ~ : t f ~ l ~

.,,4" A.4: 4 1. . . . . . . .7 5 l 2 R ~ ~ O E ' : l ~ A ~ E U ~ ~ ~ ~ D ., '-';!f;IS TO em G R A V ~ L OR CRUSHED-

STONES OF UNIFORM SIZEENLARGED SEC rim! THROUGHfiLLED DISPERSION TRENCH

FlG. 3 TVPJCAL SOIL ABSORPTION SYSTEM WITll DISpERSION TRENCHES

o-cfI l...,

~"'-Io."III'"l......,

I....10=.n

7/30/2019 is.2470.2.1985.pdf

16/24

IS : 2470 ( Par t 2 ) - 1935laid to falls with a system of underdrains laid on it and consisting of fielddrains half channels laid" upside down and open jointed, or special t i l e ~discharging to the outlet.6.2 Distribution - The septic-tank effluent should be distributed evenlyover the surface of the biological filter through which it percolates tothe floor. Biological filters may be either rectangular ( see Fig. 4.-\') orcircular (see Fig. 4B) in shape and a series of fixed channels or rotatingarm distrib"utor may be used for distributing effluent on the medium.6.3 Filter Media - The filter sand and gravel shall conform toIS: 8419 (Part 1 )-1977*.6.4 Ventilation - Adequate ventilation of biological filter is essential.Air vents communicating with the floor level of the filter should be.provided. Where the filter is below ground level, the vent pipes fromthe ends of the underdrains should be carried to 150 mm above groundlevel outside the filter. Normally the filter should not be covered, butwire netting may be used to prevent falling of leaves fouling the surfaceof the filter or blocking the ends of the vent pipe. "6.5 Volume of Filter - It is essential that the volume of filter mediumprovided is sufficient to allow for sewage flow which occurs wifh smallinstallations, such variation being more pronounced it the smallernumber of persons are served. FOf populations of up to 10 persons thevolume should be 1 m 3 of medium per head, of resident population" forover 10 and up to 50 persons, 0'8 m3 and for over 50 and up to 300persons, 0'6 m3

I f pumping of the septic tank effluent forms part of scheme,recirculation of final effluent to dilute the septic tank effluent may beintroduced to reduce the volume of the filter.6.6 TreatInent of Filter EfHuent - The filter effluent is eitherdischarged into surface drain or evenly dist ributed over" a grass plotfrom the system of channels. "Where the effluent is likely to contaminatethe watercourse, the effluent should be adequately disinfected.7. UPFLOW AN AEROBIC FILTER7.0 Upflow type of filters (reverse filter) operating under submergedconditions is a method fOf'disposal of septic tank effluents in areas Wheredense soil condition (see Table I) , high water table and limited

a v ~ i l a b i l i t y of open land are factors to be considered for successful*Requirements for filtration equipment: Part 1 Filtration media sand and gravel.

13 "

7/30/2019 is.2470.2.1985.pdf

17/24

IS : 2470 (Par t 2 ) - 1985

SUPPORT

AIR VENT TOPTO BE 150 mmABOVE GROUND. LEVEL

. /.

t-APLAN

AIR VENT

1sDISTRIBUTION CHANNELWITH SERRATED SIDES

MEDIUM

\oUNOE RDRAINSSECTION A A

"..A"oh.MEDIUM

-,-1400

==0

iUNDERDRAINS-SECT/ON 88

All dimensions in millimetres.NOTE - Flexible joints may be required on inlet or outlet connections, whererigid pipes are used.

FIG.4A RECTANGULAR BIOLOGICAL FILTER14

7/30/2019 is.2470.2.1985.pdf

18/24

r -!5, FEED PIPE

IS : 2470 ( Part 2 ) 1985AIR \ lEN'i

PLAN

J.,R VENl 10 BE i50 mm.AFGvE GROUND LEVEL

DI S TRIBU TORM ~ O I U M t

11.00~ ~ ~ ~ ~ ~ - ~CENTRE PILLARIF REQUIRED

SECTION AAAll dimensions in millimetres.

NOTE - Flexible joints may be required on inlet or outlet connectiom . where.1:'igid pipes are used.FIG. 4B CIRCULAR BIOLOGICAL FILTER

15

7/30/2019 is.2470.2.1985.pdf

19/24

IS : 2-t70 ( Par t 2 ) 1985disposal of effluents by secondary treatment. The septic tank effluentis introduced from the bottom and the microbial growth is retained onthe stone media making possible higher loading rates and efficientdigestion. The capacity of the unit is 0'04 to 0'05 m 3 per capita or 1/3to 1/2 the liquid capacity of the septic tank it serves. BOD removals of70 percent can be expected and the effluent is Clear and free from odourand nuisance, The flow sheets of the filter system are shown in Fig. 5.7.1 Types - Upflow anaerobic filters are of the following types:

a) Single chambered rectangular type,b) Double chambered rectangular type, andc) Circular type.

7.2 Cons.truction Features - In an upflow filter, the tank effluententers at the bottom through a system of underdrains, flows upwardsthrough a layer of coarse material generally 0'6 to 1'2 m deep and isdischarged over a weir or trough at the top. The driving head in theiilter, that is, the difference between the water level and the filter may beas low as 25 to 150 mm during normal functioning.7.2.1 Single Chambered Rectangular Type - In this type (Fig. 6) anupflow filter with .a rectangular chamber is constructed to treat theeffluent from a normal domestic septic tank. The chamber is packedwith coarse material and the size of the packing media should be ~ O mm.

The medium rests on a perforated concrete false bottom slab. Theeffluent from septic tank enters the bottem of the filter chamber throughalSO mm pipe and is distributed upward through the media from aperforated slab at the bottom.The vertical inlet is fitted with a tee at the bottom, one branch ofwhich leads to the filter and the other branch is kept plugged while thefilter functions. The plug can be removed to facilitate emptying into anadjoining chamber and cleaning the filter where required. The effluentfrom the top of the bed is allowed to escape over a V-notch. The silllevel is kept 150 mm above the top of the medium.

7.2.2 Double Chambered Rectangular Type - The filter consists of twointerconnected compartments (Fig. 7). The first chamber is filled to adepth of 0'55 m with 20 mm coarse medium. The second chamber isfilled to a depth of 0'45 In with 20 mm size coarse aggregate. The septictank effluent falls through a perforated tray over the medium in the firstcompartment and enters the second compartment directly frolIl thebottom. The effluent passes up through the medium in the secondchamber and esc;apes over a V-notch placed 75 :mm above the top of the16

7/30/2019 is.2470.2.1985.pdf

20/24

....

.....

IWASTE w:':- SEPTIC TANK ANAEROBICFILTER~ ....-

(1 )

GAS ItWASTE WATER ANAEROBIC GRASSFILTER PLOT

(2)

WASTE WATER SEPTIC TANK ANAEROBIC~ FILTER. -.

(3)FIG. 5 ANAEROBIC FILTER SYSTEM

GRASSPLOT.

-

EFflUENTTODRAIN

EI=FLUENTTOORAIN

DISPOSAL BY ISOAKPIT OR ITILE FIELD

....rnt..:J..-..JQ

:;'......

~....~CDCoIl

7/30/2019 is.2470.2.1985.pdf

21/24

IS : 2470 (Part 2 ) - 1985medium. By this arrangement, the time of travel of the efIluent throughthe filter is lengthened. The two chambers are each fitted at the bottomwith a 15 mm galvanized iron pipe leading to an adjacent chamber. Avalve in these pipes allows the filters to be partly desludged into thecollecting chamber.

CLEANINGCHAMBERFLOOR CAN BELOWERED TOCOLLECT SLUDGEIN BUCKET

r REMOVABLE\ SLAB Fil l E R

CHAMBER

1000

200

GL

IRE MESH SUPPORT ORPERFORATED ~ O N C R E T E BLOCK

FIG. 6 UPFLOW ANAEROBIC FILTER (SINGLE CHAMBEREDRECTANGULAR T Y P E )

TIS50SEPTIC L-

lANK

REMOVABLESLAB

J..75

4SQ

G l.

FIG .7 UPFLOW ANAEROBIC FILTER (DOUBLE CHAMBEREDRECTANGULAR T Y P E )

7.2.3 Circular Filter - A circular filter Og m in dia may also beconstructed. Medium of aggregate of uniform size 20 mm should be18

7/30/2019 is.2470.2.1985.pdf

22/24

IS : 2470 ( Part 2 ) 1985packed to rest on a perforated concrete slab. The effluent may be madeto escape over the to.p of the medium through equaJly placed notchesalong the peripheryo f the filter. The sill level is usually 100 mm abovethe top of the medium.7.3 Filter Media"'- The filter media shall conform to IS: 8'!l9( Part I )-1977*.7.4 Treat:ment of Filter Effluent - The filtEr e:-rluent shall be treatedas given in 6.6 . .

APPENDIX A( Clause 5.1 )

DETERMINATION OF THE SOIL ABSORPTION CAPACITYA-I. PERCOLATION TESTA-I.I Percolation test should be conducted as described in A-I.2 to A-I.6to determine the permeability of the soii

7/30/2019 is.2470.2.1985.pdf

23/24

IS : 2470 ( Part 2) 1985Al.4 I f no water remains in the hole, water shall be added to bring thedepth of the water in the hole till it is 150 mm over the gravel. F rom afixed, reference point, the drop in water level shall be measuredat 30 minutes intervals for 4 hours, re-filling 150 mm over the gravelas necessary. The drop that Occurs during the final 30 minutes periodshall be used to calculate the percolation rate. The drops during priorperiods provide information for possible modification of the procedureto suit local circumstances.Al.5 In sandy soils or (lther porous soils in which the first 150 mm ofwater seeps away in less than 30 minutes after the overnight swellingperiod, the time interval between measurement shall be takenas 10 minutes and the test run for one hour. The drop that occursduring the final 10 minutes shall be used to calculate the percolationrate.Al.6 Porcolation Rate - Based on the final drop, the percolationrate, that is, the time inminutes required for wa,ter to fall 25 mm, shallbe calculated.

20

7/30/2019 is.2470.2.1985.pdf

24/24

IS 2470 (Part 2 ) 1985( Continued from page 2 )

Water Supply and Plumbing Subcommittee, nne 24 : 1MembersSR.RJ]. D' CruzSEm S. A. SWAMY (Alternate)SHI\! S. G. DW)J,AI,IRAR

Repres entin!!,Municipal Corporation of DelhiIn personal capacity ( 103, Savit,i Cinema CommerrialComplex, Greater Kailash II, New Delhi)SHm S. K. DJlOIU Delhi Fire Service, New DelhiSEm R. K. BHA1WWAJ (Alternate)SIcm DEVENDRA SINGH In personal capacity ( 16 A, Maya Mahal, 17th Road,

HYDRAULIC ENGIN.I!:ER Khar, Bombay)Municipal Corporation of Greater Bombay.,BombayCn rEF ENGINEER ( S l ~ W B R , \ ( ] g ) (Alternate)SHRT R. A. KHANNA Public Health Engineering Department,SlIm D. K. Ml'l'RA (Alternate I iSHRT 1. S. BA I ~ J . \ ( Alternate I I )

Government of Madhya Pradesh, BhopalSRm S. T. KITARE Public Health Engineering Department,SHRI A. S. KULKARNI

Slim V. B. NIKAM (Alternate)Government of Maharashtra, BombayMunicipal Corporation of G r < ~ a t e r Bombay(Bombay Fire Brigade), Bombay

DIt R. P. MATRlJ.It University of Roorkee, Roorkce,SIIm C. L. TOSRNI\VAT, (Al/c:rnate)SHRI K. GOVINDA MENON Tamil Nadu Water Supply & Drainage Board,MadrasSEm T. G. SRINIV,ISAN (Alternate)SHRI V. A. MHAIBALKAlt National Environmental Engineering ResearchSRR1 C. V. CRALPA'['lHAO ( Alternate) Institute (CSIR), NagpurS:rrRI K. GOVINDAN NAIR Public Health Engineering Department,Government of Kerala, TrivandrumSlIM N. S. BHAIRAY,IN (Alternate)SHm P. K. NAGARKAR Mnharashtra Engineering Research Institllte,NasikSHRI]. N. KARDILE (Alternate )PROF. Y. N; R A M A C R A ~ D R A RAO Engineer-in-Chief's Branch ( Ministry ofMAJ B. S. PARMAn ( Alternate)SERl O. P. RATRASnBI S. K. SHARMA

Defence), New DelhiNational Buildings Organization, New DelhiCentral Building Research Institute (CSIR).Roorkee