SBR
Designed to Operate in Non steady Condition
1. Op Opera erates tes In In Batch Batch Mode Mode 2. Equalization Aeration & settlement of solid both occur in a sinle tan! usin a timed controlled sequence thus no need of clarifier and thus reduce the area.
". #apable of bearin pea!$shoc! pea!$shoc! loads as it also ser%ed ser%ed as equalization equalization tan! 4. he operatin c'cle of SBR is characterized b' fi%e periods( )1* fill (3) react, (4) settle, (5) decant and (6) idle. 5. SBRs operate operate in time time rather rather than in in space and the the number number of cycles cycles per day can can be varied to control desired effluent limits, offerin additional fle!ibility "ith an SBR 6. #n SBR can be set up to sim simula ulate te any conventi conventiona onall act activa ivated ted slude slude process process,, includin includin B$R systems.
7. %ith SBRs there is no need for return activated slude (R#S) pumps and primary slude (&S) pumps li'e those associated "ith conventional activated slude systems.
Can be designed to handle a wide range of volume unlike the conventional !" #continuous type$ designed to work under fi%ed flow. In an SBR, there are no influent or effluent currents to interfere with the settling process as in a conventional activated sludge system
&ses fine bubble' coarse bubble or (et aeration system Floating decanter is one of the most efficient, contains spring loaded plug valve.
et aeration system can mi! the content "ithout aeratin therefore it is used in both aeration and ano!ic periods.
SBR is uniquel' uniquel'
efficientt for lo+ or intermittent flo+. SBRs are typically used at efficien flo" rates of 5 *+ or less (appro!. -./ 0+* he more sophisticated operation required at larer SBR plants tends to discourae the use of these plants for lare flo+ rates.
Source: Parsons Engineering Science, !!!.
" modified version of the SBR is the 1ntermittent 2ycle !tended #eration System (12#S) . In the I#E"S system, influent wastewater flows into the reactor on a continuous $asis. "s such, this is not a true $atch reactor, as is the conventional SBR. " $affle wall may $e used in the I#E"S to $uffer this continuous inflow. %he design configurations of the I#E"S and the SBR are otherwise very similar
#fter the SBR, the batch of "aste"ater may flo" to an eualiation basin "here the "aste"ater flo"rate to additional unit processed can be controlled at a determined rate "n SBR serves as an e&uali'ation $asin when the vessel is filling with wastewater, ena$ling the system to tolerate pea( flows or pea( loads in the influent and to e&uali'e them in the $atch reactor. E&uali'ation may $e re&uired after the SBR, depending on the downstream process. If e&ua li'ation is not used prior to filtration, the filters need to $e si'ed in order to receive the $atch of wastewater from the SBR, resulting in a large surface area re&uired for filtration. Si'ing filters to accept these )$atch) flows is usually not feasi$le, "hich is "hy eualiation is used bet"een an SBR and do"nstream filtration. Separate e&uali'ation following the $iological system is generally not re&uired for most conventional activated sludge systems, $ecause the flow is on a continuous and more constant $asis. In most conventional activated sludge wastewater treatment plants, primary clarifiers are used prior to the $iological system. 7o"ever, primary clarifiers may be recommended by the SBR manufacturer if the total suspended solids (8SS) or biochemical o!yen demand (B9+) are reater than 4:: to 5:: m;0.SBR never reuire secondary clarifier.
2an be desined to handle a "ide rane of volume unli'e the conventional #S& (continuous type) desined to "or' under fi!ed flo". 1n an SBR, there are no influent or effluent currents to interfere "ith the settlin process as in a conventional activated slude system loatin decanter is one of the most efficient, contains sprin loaded plu valve. et aeration system can mi! the content "ithout aeratin therefore it is used in both aeration and ano!ic periods..
+isadvantaes... *+ " higher level of sophistication is re&uired *compared to conventional systems+, especially for larger systems, of timing units and controls. *+ -igher level of maintenance *compared to conventional systems+ associated with more sophisticated controls, automated switches, and automated valves. *+ Potential of discharging floating or settled sludge during the /R"0 or decant phase with some SBR configurations. *1+ Potential plugging of aeration devices during selected operating cycles, depending on the aeration system used $y the manufacturer. *2+ Potential re&uirement for e&uali'ation after the SBR, depending on the downstream processes.
1nfluent parameters typically include design flow, ma3imum daily flow B4/2 , %SS,%/S, p-, al(alinity, wastewater temperature, total 56eldahl nitrogen *%57+, ammonia8nitrogen *7- 8 7+, and total phosphorus *%P+ and total coliform. >or industrial "aste"ater applications, treatability studies are typically reuired to determine the optimum operatin seuence. For most municipal wastewater treatment plants, treata$ility studies are not re&uired to determine the operating se&uence $ecause municipal wastewater flowrates and characteristic variations are usually predicta$le and most municipal designers will follow conservative design approaches. +esin &arameter
unicipal
1ndustrial
:.5 ? :.4:
:.5 ? :.6:
4
@4
8ypically lo" "ater level 0SS ( m ; 0 )
@,::: ? @,5::
@,::: ? 4,:::
7ydraulic retention time ( hr )
4
Aaries
> ; ( ' B9+ ; ' 0SS . day ) 8reatment cycle duration ( hr )
Source: "&uaSBR /esign 9anual, !!2.
Table 1. Design parameters for IF-type SBR treatment systems Parameter
SBR systems
Pretreatment
Septic tank or equivalent
Mixed liquor suspended solids (mg/L)
2,000 - ,!00
"/M load (l# $%&/d/ML 'SS)
00 - 020
*+draulic retention time ()
- .0
otal c+cle times ()a
- 2
Solids retention time (da+s)
20 - 0
&ecanter over1lo ratea (gpm/1t2) Sludge asting
300 4s needed to maintain per1ormance
5+cle times sould #e tuned to e11luent qualit+ requirements, asteater 1lo, and oter site constraints
4nce the (ey design parameters are determined, the number of cycles per day, number of basins, decant volume, reactor sie, and detention times can $e calculated. "dditionally, the aeration euipment, decanter, and associated pipin can then be sied. 4ther site specific information is needed to si'e the aeration e&uipment, such as site elevation above mean sea level, "aste"ater temperature, and total dissolved solids (8+S) concentration
8he fill step is of three types . S tatic, @.mi!ed and 3. #erated Static: influent wastewater is added to the SBR partially filled with $iomass. In this condition Fm ratio is high thus sludge with high settling characteristic is produced. 9i3ed: influent is added to the SBR mi3ing the wastewater with $iomass already present in the SBR. %hus creating ano3ic condition *denitrification+
#no!ic condition a$sence of atmospheric o3ygen and microorganism utili'e the sulphates as electron acceptor to decompose the organic matter producing -S #naerobic condition a$sence of atmospheric o3ygen and microorganism utili'e the nitratesnitrites as electron acceptor to decompose the organic matter producing 7 gas *denitrification+ 9rder microorganisms first utili'e the nitrates and then sulfates.
2onstruction...
Reactors >lo" ( *+ )
>lo" ( 0+ )
$o
Sie ( ft )
Blo"ers Aolume ( * )
$o
Sie ( 7& )
:.:
:.:45
- ! @
:.:@
5
:.:
:.3/
@
@4 ! @4
:.:6/
3
.5
.@:
4.54@
@
-: ! -:
:./:-
3
@5
.::
3.-5
@
5- ! 5-
:.4/
3
4:
.4:
5.@//
@
6/ ! 6/
:.6-
3
6:
.46
5.5@6
@
- ! -
:./
4
4:
@.::
.5:
@
:./5-
3
5
4.@5
6.:-6
4
-@ ! -@ :4 ! -:
.556
5
@::
5.@:
/.6-@
4
- ! -
.35/
5
@5
7ote: %hese case studies and si'ing estimates were provided $y "&ua8"ero$ic Systems, Inc. and are site specific to individual treatment systems.
>or Bioloical $utrient Removal (B$R) plants, an SBR eliminates the need for return activated slude (R#S) pumps and pipes. It may also eliminate the need for internal 9i3ed ;i&uor Suspended Solid *9;SS+ recirculation, if this is $eing used in a conventional B7R system to return nitrate8nitrogen. %he control system of an SBR operation is more comple3 than a conventional activated sludge system and includes automatic switches, automatic valves, and instrumentation. %hese controls are very sophisticated in larger systems.
8he SBR manufacturers indicate that most SBR installations in the
2ontrol system in SBR may $e of two types . Floating < timer $ased system with P;# " P;# is an industrial grade microcomputer primarily designed to su$stitute relay logic. P;#s have an inputoutput *I4+ su$system that easily adapts to most of the water treatment plant process re&uirements. Instruments and sensors are easily connected in order to gather information for inputs to the P;#, these inputs are processed within the P;# and outputs are
generated. *I.e. an upper level sensor sends an input signal to the P;#, the information is processed according to the program and the P;# turns the system off+. For a small water treatment plant, one medium si'e P;# is enough, however, for a large water treatment plant, it may $e necessary to use several interconnected P;#s. %he P;# program automatically ad6usts the num$er of cycles $ased on the flow rate through the plant. %he num$er of cycles is varia$le *typically ranging from 1 to = cycles per day per SBR %an(+, and as the num$er of cycles increases, the duration of the react stage decreases. %he program is written in standard ladder logic and controls the plant e&uipment *actuated valves, $lowers and pumps+ $ased on input signals from field instruments such as float switches, tan( levels, current draws, alarms, hour meters readings, pump and $lower running status, and actuated valve status. 5ey process controls are ad6usta$le $y the plant operator through the P;# interface to allow changes to process and alarm set point values.
.
P# $ased S#"/" system " supervisionary control and data ac&uisition system *S#"/"+ often represents the human machine interface in a water treatment controly system. 0hile a P;# effectively provides an effective control of a process they are oftenly scattered around the water treatment plant. %he S#"/" is installed in order to collect and analy'e input from all these P;#s and to provide an interface for the plant operator to interact with the control system. " S#"/" system gather the information as hard points *raw data from the P;# or other device+ and soft points *processed data from hard points+ and store them in a data $ase, therefore reports and other supervisionary information is easily created and accesed $y the operators. "ccess to the control system is typically through a graphical computer interface Supervisory #ontrol "nd /ata "c&uisition *S#"/"+ interface, such as >isual %ag System *>%S %9+ operator interface, running on a dedicated P# computer. %his ena$les process ad6ustments and logging datatrends of levels and alarms. 4perator ad6usta$le process varia$les are accessi$le through the computer interface. %he interface also ena$les access to logged information on float switch positions, tan( levels, alarms, hour meters readings, pump and $lower running status, etc. %he levels in the reactors are monitored $y pressure transducers mounted in each reactor tan(. %he >%S provides accurate metering of the flow through the plant eliminating the need for a plant flow meter. %he control system can $e accessed from virtually anywhere in the world using a computer, software, modem lin( and telephone access. By this method the operator and support personnel can remotely chec( plant status and operational trends. %his is particularly useful for alarm )call outs) so the operator can chec( the priority of the call and determine $efore leaving home *or a remote office+ the type of response re&uired. "lso if the operator is away for a period of time, the operator can chec( the plant status $y a modem lin( from anywhere in the world. %he data ac&uisition is particularly useful for trou$le shooting the plant. %he system will incorporate a dialer for alarms.
8an': . for municipal wastewater ? concrete tan( . For industrial wastewater: steel with inside ru$$er liner i!in C #eration System .@et aeration systemA allow mi3ing either with or without aeration, .fine . < coarse $u$$le aeration system
Blowers: positive displacement type /ecanter: . floating typefloating type, offer the operating fle3i$ility to vary fill8and8draw volumes. . Fi3ed type
&erformance... %he performance of SBRs is typically compara$le to conventional activated sludge systems and depends on system design and site specific criteria. /epending on their mode of operation, SBRs can achieve good B4/ and nutrient removal. For SBRs, the B9+ removal efficiency is enerally -5 to /5 percent . SBR manufacturers "ill typically provide a process uarantee to produce an effluent of less thanD *+ mg ; B4/, *+ mg ; %SS, *+ 2 8 = mg ; %7 and *1+ 8 mg ; %P
9peration and aintenance... Since the heart of the SBR system is the controls, automatic valves, and automatic switches, these systems may re&uire more maintenance than a conventional activated sludge system. "n increased level of sophistication usually e&uates to more items that can fail or re&uire maintenance. 8he level of sophistication may be very advanced in larer SBR "aste"ater treatment plants reuirin a hiher level of maintenance on the automatic valves and s"itches. Significant operating fle3i$ility is associated with SBR systems. #n SBR can be set up to simulate any conventional activated slude process, includin B$R systems. For e3ample, holding times in the "erated React mode of an SBR can $e varied to achieve simulation of a contact sta$ili'ation system with a typical hydraulic retention time *-R%+ of .2 to C hours or, on the other end of the spectrum, an e3tended aeration treatment system with a typical -R% of = to D hours. >or a B$R plant, the aerated react mode (o!ic conditions) and the mi!ed react modes (ano!ic conditions) can be alternated to achieve nitrification and denitrification. %he mi3ed fill mode and mi3ed react mode can $e used to achieve denitrification using ano3ic conditions. 1n addition, these modes can ultimately be used to achieve an anaerobic condition "here phosphorus removal can occur . #onventional activated sludge systems typically re&uire additional tan( volume to achieve such fle3i$ility. SBRs operate in time rather than in space and the number of cycles per day can be varied to control desired effluent limits, offerin additional fle!ibility "ith an SBR.
>or B$R first aerobic then ano!ic condition alternately >or B&R only anaerobic condition Table 2. Suggested maintenance for seuencing batc! reactor pac"age plants Systems component
Suggested maintenance tas"s
6eaction tank
5eck 1or 1oaming and uneven air distri#ution7 ceck 1or 1loating scum7 ceck decanter operation and ad8ust as required7 ad8ust c+cle time sequences as required to acieve e11luent target concentrations7 ceck settled sludge volume and ad8ust aste pumping to maintain target ML'SS levels
4eration s+stemdi11used air
5eck air 1ilters, seals, oil level, and #ackpressure7 per1orm manu1acturer9s required maintenance
4eration s+stemmecanical
5eck 1or vi#rations and overeating7 ceck oil level, and seals7 per1orm manu1acturer9s required maintenance
Septic tank (primar+ clari1ier)
5eck 1or accumulated solids and order pumping i1 required
5ontrols
5eck 1unctions o1 all controls and alarms7 ceck electrical control #ox
Sludge asting
Pump aste solids as required to maintain target ML'SS range (t+picall+ !00 to ,000 mg/L)
4nal+tical
Measure aeration tank gra# sample 1or ML'SS, p*, and settlea#ilit+7 collect 1inal e11luent decant composite sample and anal+:e 1or ater qualit+ parameters as required ($%&, SS, p*, ;, P, etc)
2osts...
+esin flo"rate ( *+ )
uipment costs (
:.5 ? .:
./6 ? 5.::
. ? .5
.-3 ? @.6/
.5 ? @.:
.65 ? 3.@/
7ote: Installed cost estimates o$tained from "&ua8"ero$ics Systems, Inc., "ugust !!=.
