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CHAPTER 1.0
INTRODUCTION
1.1 General
Sewage is created by residential, institutional, and commercial and industrial establishments and
includes household waste liquid from toilets, baths, showers, kitchens, sinks and so forth that
is disposed of via sewers. In many areas, sewage also includes liquid waste from industry and
commercial establishments. The separation and draining of household waste into greywater
and blackwater is becoming more common in the developed world, with greywater being
permitted to be used for watering plants or recycled for flushing toilets. Most sewage also
includes some surface water from roofs or hard-standing areas and may include storm water
runoff.
Sewerage systems capable of handling storm water are known as combined systems or
combined sewers. Such systems are usually avoided since they complicate and thereby
reduce the efficiency of sewage treatment plants owing to their seasonality. The variability in
flows also leads to often larger than necessary, and subsequently more expensive, treatment
facilities. In addition, heavy storms that contribute more flows than the treatment plant may
overwhelm the sewage treatment system, causing a spill or overflow. Modern sewered
developments tend to be provided with separate storm drain systems for rainwater.
As rainfall travels over roofs and the ground, it may pick up various contaminants
including soil particles and other sediment, heavy metals, organic compounds, animal waste,
and oil and grease. Some jurisdictions require storm water to receive some level of treatment
before being discharged directly into waterways. Examples of treatment processes used for
storm water include retention basins, wetlands, and buried vaults with various kinds of media
filters, and vortex separators (to remove coarse solids). Sanitary sewers are typically much
smaller than storm sewers, and they are not designed to transport storm water. In areas with
basements, backups of raw sewage can occur if excessive storm water is allowed into a
sanitary sewer system.
Sewage treatment, or domestic wastewater treatment, is the process of removing
contaminants from wastewater and household sewage, both runoff (effluents) and domestic.
It includes physical, chemical, and biological processes to remove physical, chemical and
biological contaminants. Its objective is to produce a waste stream (or treated effluent) and a
1
solid waste or sludge suitable for discharge or reuse back into the environment. This material
is often inadvertently contaminated with many toxic organic and inorganic compounds.
1.2 Wastewater Treatment Plants
Wastewater Treatment Plants are engineered systems planned, designed and constructed
for management of wastewater (domestic, industrial or commercial wastewaters) with
application of principles Environmental Engineering to protect natural systems from
pollution. Sewage can be treated close to where it is created (in septic tanks, bio filters or
aerobic treatment systems), or collected and transported via a network of pipes and pump
stations to a municipal treatment plant. Sewage collection and treatment is typically subject to
local, state and federal regulations and standards. Industrial sources of wastewater often
require specialized treatment processes.
Many processes in a wastewater treatment plant are designed to mimic the natural
treatment processes that occur in the environment, whether that environment is a natural
water body or the ground. If not overloaded, bacteria in the environment will consume
organic contaminants, although this will reduce the levels of oxygen in the water and may
significantly change the overall ecology of the receiving water. Native bacterial populations
feed on the organic contaminants, and the numbers of disease-causing microorganisms are
reduced by natural environmental conditions such as predation or exposure to ultraviolet
radiation. Consequently, in cases where the receiving environment provides a high level of
dilution, a high degree of wastewater treatment may not be required. However, recent
evidence has demonstrated that very low levels of specific contaminants in wastewater,
including hormones (from animal husbandry and residue from human hormonal
contraception methods) and synthetic materials such as phthalates that mimic hormones in
their action, can have an unpredictable adverse impact on the natural biota and potentially on
humans if the water is re-used for drinking water. A significant threat in the coming decades
will be the increasing uncontrolled discharges of wastewater within rapidly developing
countries.
Methods of treatment in which the application of physical forces predominates are known
as unit operations and the removal of contaminants is brought by chemical or biological
reactions are known as unit processes. At present these two categories of treatment methods
are grouped together to provide what is known as primary, secondary, and tertiary treatment.
In primary treatment, physical operations such as screening and sedimentation are used to
2
remove the floating and settleable solids found in wastewater. In secondary treatment,
biological and chemical processes are used to remove most of the organic matter. The
additional combinations of unit operations and processes form tertiary treatment which are
used to remove other constituents, such as nitrogen and phosphorus, that are not reduces
significantly by secondary treatment.
1.3 About Bangalore Water Supply and Sewerage Board (BWSSB)
Bangalore is located on the watershed of two principal river basins, Arkavathi to the west
and South, Pennar to the East. The local topography is characterized by a series of well
defined valleys which radiate from a ridge of High Ground to the north of the city and fall in
a gradual manner towards wide belt of flat land extending beyond the limits of the
metropolitan area to the South.
The Three principal valleys are known as Vrishabhavathi, Koramangala and Challaghatta
and three valleys run generally in a north to the south direction and divide the greater part of
the metropolitan area which lies to the south of the ridge into three separate and distinct
drainage zones. A fourth valley system referred to as the Hebbal series forms drainage zone
to the north of the ridge and runs in north easterly direction.
Five minor valleys, the Kathriguppa and Tavarekere to the south, the Arkavathi and
Kethamaranahally to the north west and Marathhally to the east, lie outside the tributary area
of the major valleys and they drain independently to the fringe areas which form the
remainder of the metropolitan area.
The configurations of valleys in well graded side slopes of their tributary areas have
provided Bangalore with a natural system of drainage without recourse to pumping. Both
sewerage and storm water flow by gravity beyond the city.
The system of sewers for the conveyance of domestic and industrial waste water through
underground drainage system was introduced in the year 1922. The system introduced
initially was confined to heavily populated area in the heart of the city and although a gradual
extension took place then onwards it was not until 1950 that a major programme of sewer
construction was commenced. With the formation of the Board (BWSSB) in 1964, the
programme to provide Sewerage system in the unsewered areas was taken up in a phased
manner and the treatment of sewage before it is led into the natural valleys was also tackled.
3
At present, Bangalore city has a well designed and regularly maintained underground
sewerage system. Stoneware pipes are used up to 300 mm dia. Sizes and RCC hume pipes
varying in Dia. from 300 mm to 2000 mm for sub-mains/mains/outfall sewers.
In order to facilitate easy cleaning in sewer lines whenever blockage occurs in sewer line,
adequate numbers of manholes are provided at regular intervals’. Manholes with cast iron
frames and covers are provided in heavy traffic roads, on small lanes and cross roads with
less traffic with RCC frames and covers for the manholes.
This report discusses the training undergone during June-July ’10 as a part of the M.Tech
course work at 180 MLD Sewage Treatment Plant, Vrishabhavathi Valley maintained by
Bangalore Water Supply and Sewerage Board.
1.4 Objectives
The main aim of undergoing practical training, which is a part of our course, is to study
the processes adopted in the Sewage Treatment Plant. The specific objectives of this study
are:
To gain knowledge of the treatment processes adopted in the plant.
To study the Operation & Maintenance procedures of the plant in brief.
To analyse the performance criteria of the treatment units by conducting analyses at
plant laboratory.
4
CHAPTER 2.0
LITERATURE REVIEW
2.1 Sewage Treatment Facilities
There has been a change every now and then, since the concept of wastewater
management or treatment was started. The methods of treatment that were predominant in
late 1980’s and 1990’s are now seen as conventional or outdated at some places. Researchers
and Engineers have always found new ways to treat the polluted waters and curb pollution to
greater extent. These facilities or methods or processes what we use now are the greatest
contribution of those most dedicated and eminent people who have our lives so easy now. In
this section, the salient features of treatment facilities that are been adopted since decades
will be discussed in brief.
Wastewater treatment methods have been classified into well established categories
like physical unit operations, chemical unit processes and biological unit processes. The
objectives of these methods are briefed in section 1.2. The application of treatment methods
is the major part in designing any treatment facilities. Having known the treatment methods
available and the benefits of them, designing of treatment units does not become difficult
provided one has understood the objectives that has to be met. The principal methods now
used for wastewater treatment and sludge are identified here.
2.2 Wastewater Processing
As noted in chap. 1 that unit operations and processes are grouped together to provide
various levels of treatment. The term “preliminary” and/or “primary” referred to physical unit
operations; “secondary” referred to chemical and biological unit processes; and “tertiary” or
“advanced” referred to combinations of all three. The unit operations and processes necessary
to achieve that required level of treatment are grouped together on the basis of fundamental
considerations. Application of these operations, processes, and methods to perform specific
functions is described in the following sections.
2.2.1 Preliminary Wastewater Treatment
This is defined as the removal of wastewater constituents that may cause maintenance
or operational problems with the treatment operations, processes, and ancillary systems.
Examples of preliminary operations are screening and comminution for the removal of debris
5
and rags, grit removal for the elimination of coarse suspended matter that may cause wear or
clogging of the equipment, and floatation for the removal of large quantities of oil and grease.
2.2.2 Primary Wastewater Treatment
In primary treatment, a portion of the suspended solids and organic matter is removed
from the wastewater. This removal is usually accomplished with physical operations such as
screening and sedimentation. The effluent from primary treatment will ordinarily contain
considerable organic matter and will have a relatively high BOD. The principal function of
primary treatment will continue to be as a precursor to secondary treatment.
2.2.3 Conventional Secondary Wastewater Treatment
Secondary treatment is directed towards the removal of biodegradable organics and
suspended solids. Disinfection is included frequently in the definition of conventional
secondary treatment. This is defined as the combination of processes customarily used for the
removal of theses constituents and includes biological treatment by activated sludge, fixed-
film reactors, or lagoon systems and sedimentation.
2.2.4 Advanced Wastewater Treatment/Wastewater Reclamation
Advanced wastewater is defined as the level of treatment required beyond
conventional secondary treatment to remove constituents of concern including nutrients, toxic
compounds, and increased amounts of organic material and suspended solids. In addition to
the nutrient removal processes, unit operations or processes frequently employed in advanced
wastewater treatment are chemical coagulation, flocculation, and sedimentation followed by
filtration and activated carbon. These are used in variety of reuse applications where high
quality water is required.
2.2.5 Sludge Processing
Sludge processing and disposal methods play an important role in waste management
that arise from treatment plants itself. The sludge contains high concentrations of organic
matter and other trace pollutants which are of both highly beneficial and detrimental
characteristics. Sludge being liquid portion of the wastewater is easy to handle and process.
Unlike wastewater treatment sludge processing also has unit operations and processes for
final disposal of sludge. Examples of these include thickening, stabilization, conditioning,
dewatering, heat drying etc, and are employed to prepare sludge for final disposal.
6
2.3 Conventional Trickling Filters
Trickling filters are used for the biological treatment of domestic sewage and
industrial wastes which are amenable to aerobic biological processes. Trickling filters possess
a unique capacity to handle shock loads and provide dependable performance with a
minimum of supervision.
The trickling filter consists of a permeable bed of medium through the sewage or
liquid waste is allowed to percolate. The materials used as filter medium include crushed or
broken rock, gravel, blast furnace slag or inert synthetic materials such as plastics and
ceramics. Randomly packed solid media like rock, gravel and slag are characterised by lower
porosities (40-60%), lower specific surface areas (40-70 m2/m3) and lower depths of 0.9 to
2.5 m. Plastic media of various shapes possess very high porosities (94-97%) and higher
specific surface areas (80-200 m2/m3). While conventional filters usually employ rocks,
gravel and slag as filter medium, plastic media are generally used in super rate filters which
operate at much higher hydraulic and organic loading rates and are much deeper (up to 12 m)
compared to conventional filters. The deep filters containing plastic media are referred to as
biotowers and have been used for both domestic and strong industrial wastewaters. The
trickling filters may be generally circular but square or rectangular shapes may also be used.
The sewage is evenly distributed on the surface of filter medium and the treated effluent is
collected by the underdrains.
The trickling filter is preceeded by primary sedimentation so that the settleable solids
in the sewage may not clog the filter. The sedimentation tanks should have skimmers to
remove the scum. The filter is always followed by a final settling tank to remove from the
filter effluent the settleable organic solids produced in the filtration process. In some cases, it
may be advantageous to provide skimming devices for the final settling tanks also. The
trickling serves both to oxidise and bioflocculate the organic material in sewage and their
efficiency is assessed on the total reduction in BOD affected through the filter and the
subsequent settling tank, since the effluent quality is reckoned after the settlement of the
bioflocculated solids.
2.4 Tertiary Treatment Systems
Advanced wastewater treatment is defined as the additional treatment needed to
remove suspended, colloidal and dissolved constituents remaining after conventional second-
7
ary treatment. Dissolved constituents may range from relatively simple inorganic ions, such
as calcium, potassium; sulphate, nitrate, and phosphate, to an ever-increasing number of
highly complex synthetic organic compounds, in recent years, the effects of many of these
substances on the environment have become understood more clearly.
Research is ongoing to determine (1) the environmental effects of potential toxic and
biologically active substances found in wastewater and (2) how these substances can be
removed by both conventional and advanced wastewater-treatment processes. As a result,
wastewater-treatment requirements are becoming more stringent in terms of both limiting
concentrations of many of these substances in the treatment plant effluent and establishing
whole effluent toxicity limits. To meet these new requirements, many of the existing
secondary Treatment facilities will have to be retrofitted and new advanced wastewater
treatment facilities will have to be constructed.
The need for advanced wastewater treatment is based on a consideration of one or more
of the following factors.
1. The need to remove organic matter and total suspended solids beyond what can be
accomplished by conventional secondary treatment processes- to meet more stringent
discharge and reuse requirements.
2. The need to remove residual total suspended solids to condition the treated wastewater
for more effective disinfection.
3. The need to remove nutrients beyond what can be accomplished by conventional
secondary treatment processes to limit eutrophication of sensitive water bodies.
4. The need to remove specific inorganic (e.g., heavy metals) and organic constituents
(e.g., MBTF and MDMA) to meet more stringent discharge and reuse requirements for
both surface water and land-based effluent dispersal and for indirect potable reuse
applications (e.g., groundwater recharge).
5. The need to remove specific inorganic (e.g., heavy metals, silica) and organic
constituents for industrial reuse (e.g.. cooling water, process water, low-pressure boiler
makeup water, and high-pressure boiler water).
With increased scientific knowledge derived from laboratory studies and environmental
monitoring concerning the impacts of the residual constituents found in secondary effluent, it
is anticipated that many of the methods now classified as advanced will become conventional
within the next 5 to 10 years.
8
CHAPTER 3.0
PRACTICAL TRAINING
3.1 Vrishabhavathi Valley (V-Valley) 180 MLD Sewage Treatment Plant
The Vrishabhavathi valley STP treatment plant has been constructed to treat sewage
generated in the western part of the city. This plant is situated near Nayandahalli in
Bangalore-Mysore road. Capacity of the treatment plant is 180 MLD with Secondary
treatment facilities and 60 MLD of the treated sewage is sent for tertiary treatment.
Initially plant was designed for Primary treatment of 27 MGD (123 MLD) in the year
1974 for the same drainage area. Wastewater generated from 6 areas, Malleshwaram,
Vijayanagar, Attiguppe, Chamrajapete, Market, and Hanumanthnagar is collected and
transported to STP through well designed sewer system. Due to rapid increase in population
and industrial activities, the plant was expanded to treat 180 MLD & upgraded the treatment
upto secondary levels in the year 1999.
The existing secondary treatment plant was commissioned in year 1999 and is spread
over 93 acres next to the state highway connecting Bangalore & Mysore. The sewage from
drainage area of 9910 acres has been brought to the plant by an inlet pipe (outfall sewer) of
diameter 1800 mm. The plant was designed to treat sewage characteristics with BOD 350
mg/L and suspended solids 460 mg/L. The plant is expected to remove 60% solids and 65%
of BOD.
The treatment process adopted in this plant is “Conventional two stage trickling filter
(bio-filters) process” which consists of the following units. The general flow diagram of
units in STP is given in the Fig 3.1.
1. Primary Treatment Units:
a. Screening b. Grittingc. Primary clarifier d. Primary Bio-filters e. Recirculation pump housef. Sludge pumping
2. Secondary Treatment:
a. Secondary Bio-filtersb. Secondary clarifier
9
c. Sludge pumpingd. Sludge drying beds
10
30%
INLET
MS
CS
FS
GT3 GT 1 GT 2
PC 1 PC 2 PC 3
PBF 4PBF 1 PBF 2 PBF 3
SBF 1 SBF 2 SBF 3SBF 4
SC 1 SC 2 SC 3SC 4
OUT CHANNEL60 MLD TO TTP
PC 5PC 4
V. VALLEY
Fig 3.1: General flow diagram of 180 MLD STP at V-Valley
11
Manure WW to V.Valley
WW to Inlet
WET WELL
SD 1 SD 2 SD 3 SD 4 SD 5
Sludge from pc & SC
SDBS
Fig 3.2: Flow diagram for sludge handling in 180 MLD STP at V-Valley
Abbreviations of the Flow chart 3.1 & 3.2
CS- Coarse Screen SD- Sludge Digester
MS- Medium Screen DBS- Sludge Drying Beds
FS- Fine Screen Sludge flow
GT- Grit Chamber Supernated Liquid from Digester
PC- Primary Clarifier Flow of wastewater
SC- Secondary Clarifier
PBF- Primary Biofilter
SBF- Secondary Biofilter
SC- Secondary Clarifier
Flow of wastewater
Recirculation
12
3.2 Detailed Description of the Units
3.2.1 Screens
The main purpose of installation of screens is to remove the floating matter of
comparatively large size. This reduces the problem of choking of pumps and pipes by
removing floating materials which are usually wooden pieces, plants, dead animals, plastic
materials, etc which are hindrance to free flow in pipes. Screening is done in three stages i.e.,
Coarse screens, medium screens and fine screens. The specifications of these screens are
given below.
Existing Screens at V-Valley STP
Coarse Screens:
Number of screens : 1 Type : Bar Screen Dimensions : 2.65 m x 4.25 m Clear opening between bars : 75 mm Type of cleaning : Manual Inclination of screens : 45°
Medium Screens:
Number of screens : 2 Type : Bar Screen Dimensions : 1.8 m x 2.1 m Clear opening between bars : 40 mm Type of cleaning : Manual Inclination of screens : 45°
Fine Screens: Number of screens : 3 (2W+1S) Type : Bar Screen Dimensions : 1.8 m x 2.1 m Clear opening between bars : 20 mm Type of cleaning : Manual Inclination of screens : 60°
3.2.2 Grit Chambers
Grit chambers are designed to remove grit, consisting sand, gravel, cinders, or other
heavy solid materials that have subsiding velocities or specific gravities substantially greater
than those of the organic putrescible solids in wastewater. Girt chambers are most commonly
located after the bar racks and before the primary sedimentation tanks.
13
Grit chambers are provided to (1) protect moving mechanical equipment from
abrasion and accompanying abnormal wear; (2) reduce formation of heavy deposits in
pipelines, channels, and conduits; and (3) reduce the frequency of digester cleaning caused by
excessive accumulations of grit. The removal of grit is essential ahead of centrifuges, heat
exchangers, and high-pressure diaphragm pumps.
There are three general types of grit chambers: horizontal-flow, of either a rectangular
or a square configuration; or vortex type. The plant has horizontal-flow type grit chambers,
where flow passes through the channel in a horizontal direction and the straight line flow
velocity is controlled by the dimension of the unit, an influent distribution gates and a weir at
the effluent end.
Existing Grit Chambers at V-Valley STP
Grit chambers:
Type : Detritors with classifiers Number of Units : 3 (2+1)
a. 2 units with dimensions 11.80 m x 11.80 m x 2 m (SWD)b. 1 unit with dimension 7.50 m x 7.50 m x 0.75 m (SWD)
Number of classifier : 3 Over flow rate : 1090 m3/m2/d Detention time : 60-80 seconds
The grit is generally used to reclaim the low lying land. It can also be mixed with poor
soil to condition it. The soil mixed with grit works as good manure for the garden crops.
3.2.3 Primary Clarifiers & Secondary Clarifiers
Primary clarifiers are located just after the grit chambers and they are thus provided to
treat raw sewage. The main objective of providing primary clarifiers is to hold the sewage in
the tank for about 2.5 hours, which allow for about 65% or more, suspended solids to settle to
the bottom and removed by mechanical scraper as primary sludge. Here the Degritted sewage
is fed at the centre of the clarifier.
The wastewater from secondary trickling filters is pumped to secondary clarifier for
settling of organic matter and to oxidise it. After the settlement of organic matter the water is
pumped for tertiary treatment and remaining effluent is let in to the nearby valley.
14
Clarifier has various parts which perform specific functions. Scum baffles are
provided near the outlet channel to prevent the entry of floating substances in to the outlet
channel. Scum removal devices to collect all the scum that has been removed by scum baffles
and is further sent either for further treatment or for final disposal. Sludge accumulated at the
bottom of the tank should be removed periodically.
Existing Primary Clarifiers & Secondary Clarifiers at V-Valley STP
Primary Clarifiers:
Number of tanks : 5 Type : Circular Diameter
a. 1&2 units - 47.26 mb. 3, 4 & 5 - 52 m
Volumea. 1&2 units – 6665 m3
b. 3, 4 & 5 units – 10542 m3
Detention timea. 1&2 units – 2.6 hoursb. 3, 4 & 5 units – 3-5 hours
Side water deptha. 1&2 units – 3.80 mb. 3, 4 & 5 units – 3.99 m
Surface loading rate : 32 m3/m2-d Weir loading : 220 m3/m2-d Primary effluent quality : BOD – 200 mg/L & SS – 210 mg/L
Primary clarified water is sent to primary bio-filters for removal of organic matter.
There are 4 primary bio-filters in the plant, 3 working and 1 standby. The sludge from
clarifiers is removed hydraulically, every 2-3 hour and collected in wet wells for pumping it
to sludge drying beds.
Secondary Clarifiers:
Number of tanks : 4 Type : Circular Diameter : 59 m Volume : 5681 m3
Detention time : 4 hours Side water depth : 2.08 m Surface loading rate : 20 m3/m2-d
15
Weir loading : 160 m3/m2-d Final effluent quality : BOD – 20 mg/L & SS – 30 mg/L
Solids (sludge) produced is pumped to wet wells and then to sludge drying beds.
3.2.4 Primary and Secondary Bio-filters
The main objective of providing trickling filters is to reduce BOD content. By using
trickling filters 90% of the BOD will be reduced. Trickling filters contain permeable bed of
coarse filtering media through which the sewage or liquid waste is allowed to sprinkle or
trickle down through rotary distributors. The percolating sewage is collected at the bottom of
the tank through a well designed under drainage system. The purification of the sewage is
brought about mainly by the aerobic bacteria, which forms a bacterial film around particles of
the filtering media. In order to ensure the large-scale growth of the aerobic bacteria, sufficient
quantity of oxygen is supplied by providing suitable ventilation facilities in the body of the
filter, and also to some extent by the intermittent functioning of the filter.
Existing Primary Trickling filters & Secondary Trickling filters at V-Valley STP
Primary Trickling filters:
Number of filters : 4 Type : Circular Diameter : 61.8 m Depth : 1.67 m Hydraulic loading rate : 30 m3/m2-d Organic loading : 1.8 Kg BOD/ m3-d Recirculation ratio : 1.0 Filter media : Granite Filter media nominal size : 150-200 mm
The effluent from primary trickling filter is allowed in to secondary trickling filter.
Secondary Trickling filters:
Number of filters : 4 Type : Circular Diameter : 61.8 m Depth : 1.17 m Hydraulic loading rate : 30 m3/m2-d Organic loading : 1.8 Kg BOD/ m3-d Recirculation ratio : 1.0
16
Filter media : Granite Filter media nominal size : 150-200 mm
3.2.5 Sludge Pumping
The sludge withdrawn from the clarifiers is collected in sludge wet wells and pumped
to drying beds from there. Pumps with the help of float switches start automatically to pump
it to sludge drying beds. The existing sludge digesters are not in working condition hence the
sludge id pumped directly to drying beds. The sludge pumps are non-clog pumps type with a
pumping capacity of 900 lpm of raw sludge.
3.2.6 Sludge Drying Beds
The collected sludge from wet wells is pumped to drying beds. The deposition is done
evenly upon the beds of size 20 m x 30 m up to a depth of 20 cm. The dissolved gas tries to
come up and float leaving a clear liquid at the bottom, which drains through the sand rapidly.
The evaporation process takes place about 15-20 days. The liquid from under drains is
disposed of by discharging in to valley. The dries cake becomes compact, impervious and in
dark colour is removed by shovels and is used as fertilizer. The details of sludge, grit and
other wastes produced in STP are tabulated in the Table 3.1.
Table 3.1: Details of wastes produced and disposal of the wastes
Sl. No Unit Waste generated Quantity kg/day Disposal
1 Screen Screens 72 Open dumping
2 Grit chamber Grit 150 manure
3 Primary clarifier Sludge 150 manure after drying
4 Secondary clarifier Sludge 75 manure after drying
5 Clarifiers scum 50 Open dumping
Existing Sludge drying beds at V-Valley STP
Sludge Drying Beds:
Number of beds : 30
Length of the beds : 40.85 m
Width of beds : 11.40 m
17
Total area of drying beds : 466 m2
Depth of sludge to beds : 0.2 m
Time to dry sludge : 15 days
3.3 Observations and Data Collected with Interpretation
Observations made during period of training i.e., from 1st June –15th July and the
technical data collected with plots and tables are presented in this section. The detailed list of
working and standby units in STP is given in Table 3.2 below.
Table 3.2: Units in STP
Units No. of Units Unit No.
Total Working Standby Working Standby
Screens
a. Coarse
b. Medium
c. Fine
1 1 - 1 -
4 3 1 1, 2, 3 4
3 2 1 1 & 3 2
Grit chambers 3 2 1 2 & 3 1
Primary Clarifier 5 2 1 1, 2 & 3 4 & 5
Primary Bio-filter 4 1 3 1 2, 3 & 4
Secondary Clarifier 4 1 3 4 1, 2 & 3
Secondary bio-filter 4 2 2 2 & 3 1 & 4
The table above gives the details of units that were operated during the training
period. As the flow was less compared to designed value, only required units were in
operation keeping other units as standby. The flow details are given in the following section.
3.3.1 Flow Measurement
The daily flow patterns were measured every hour using graduated scale. The over
flow depth at the weirs of grit chambers 1, 2, & 3 are measured with the scale and the flow
(calculated using rectangular weir over flow) corresponding to the depth is noted. The details
of flow for the month June-July is given in the following Table 3.3.
18
The flow expected was less to the plant because of the dry season. The flow varied
from a minimum of 27 MLD to a maximum of 117 MLD.
Table 3.3: Flow in MLD corresponding to the depth noted at time of measurement
Sl. No Depth in cmGrit tank 1& 2 flow in MLD
Grit tank 3flow in MLD
1 1 1.03 1.47
2 2 2.93 3.99
3 3 5.39 7.34
4 4 8.3 11.13
5 5 11.6 15.19
6 6 15.26 20.76
7 7 19.23 26.16
8 8 23.49 31.96
9 9 28.04 38.14
10 10 32.84 44.67
11 11 37.88 51.53
12 12 43.17 58.72
13 13 48.67 66.21
14 14 54.4 74.6
15 15 60.33 82.06
16 16 66.46 90.41
17 17 72.79 99.01
18 18 79.3 111.53
19 19 86 114.05
20 20 92.88 117.07
21 21 99.84 125.14
19
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
0
20
40
60
80
100
120
140
Daily Flow Variation June 2010
Minimum Flow
maximum Flow
Average Flow
Days
Flo
w M
LD
Fig 3.3: Plot of daily flow variation for the month June 2010
1 2 3 4 5 6 7 8 9 10 11 120
20
40
60
80
100
120
140
Daily Flow Variation July 2010
Minimum Flow
maximum Flow
Average Flow
Days
Flo
w M
LD
Fig 3.4: Plot of daily flow variation for the month July 2010
3.3.2 Sampling
The laboratory facility at the STP was well equipped for the required analysis to be
carried out to determine the effluent quality before discharging into the valley. Sampling was
done every hour which formed the grab samples and mixed after 6 hours to make a composite
sample before analysis.
20
Sampling points
Sample point 1: Outlet of Grit chamber Sample point 2: Clarified water from primary clarifier Sample point 3: Clarified water from secondary clarifier
After mixing of samples at each point separately, samples were brought to the
laboratory for analysis. The parameters analyzed are given in the Table 3.4 with the methods
of determination. A log book is maintained to keep a record of analysis results and is dully
signed daily by the Assistant Executive Engineer of the plant.
Table 3.4 Parameters and methods used for the analysis of samples
Parameter Method
Temperature Direct measurement
pH Litmus colour comparison with standard pH scale
Dissolved Oxygen (DO) Modified Winkler’s method
Chemical oxygen demand (COD) Closed Reflux method
Bio-chemical oxygen demand (BOD) Modified Winkler’s method
Suspended solids ODYSSEY HACH, Spectrophotometry method
3.3.3 Analysis Data
The results of analyses for the month of June-July are given in the figures below. The
data tabulated is given in the Annexure-I.
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
0
5
10
15
20
25
30
35Temperature June - July 2010
InletIntermediateOutlet
Days
Tem
per
atu
re 0
C
Fig 3.5: Plot of Temperature for the month June-July 2010
21
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
6.4
6.6
6.8
7
7.2
7.4
7.6
7.8pH June - July 2010
Inlet
Intermediate
Outlet
Days
pH
Fig 3.6: Plot of pH for the month June-July 2010
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Dissolved Oxygen June- July 2010
Inlet
Days
DO
mg/
l
Fig 3.7: Plot of Dissolved Oxygen for the month June-July 2010
22
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
0
100
200
300
400
500
600
700
800
900
COD June- July 2010
Inlet
Intermediate
Outlet
Days
CO
D m
g/l
Fig 3.8: Plot of COD for the month June-July 2010
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
0
50
100
150
200
250
300
350
400
450
5 day BOD June - July 2010
Inlet
Intermediate
Outlet
Days
BO
D5
mg/
l
Fig 3.9: Plot of 5 Day BOD for the month June-July 2010
23
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
0
100
200
300
400
500
600
700
Suspended Solids June- July 2010
Inlet
Intermediate
Outlet
Days
SS
mg/
l
Fig 3.10: Plot of Suspended Solids for the month June-July 2010
1 2 3 4 5 6 7 8 9 1011121314151617181920212223242526272829300
10
20
30
40
50
60
70
80
90
Percentage reduction in COD @ STP June 2010
Days
% r
educ
tion
in C
OD
Fig 3.11: Plot of % reduction in COD
24
1 2 3 4 5 6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
0
10
20
30
40
50
60
70
80
90
100
Percentage BOD5 reduction @ STP June 2010
Days
% r
educ
tion
BO
D5
Fig 3.12: Plot of % reduction in BOD
1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293070
75
80
85
90
95Percentage SS reduction @ STP in June 2010
Days
% r
educ
tion
of S
S
Fig 3.13: Plot of % reduction in SS
25
3.4 Operation & Maintenance
Since STP units have various moving mechanical and electrical equipments and
machineries, problems are more often to occur. The problems that occurred in operation of
units in STP are given in the Table 3.5. An operation and maintenance log book is maintained
to record the problems that occur and maintenance measures taken.
Table 3.5: Operational Problems encountered in STP during June-July 2010
UnitUnit No Problems
Screen Screens No problem encountered
Grit Chamber Grit no 2 Breakage of chain due to heavy silt collection in the tank
Primary Clarifier PC 1 Stop due to wheel track problem
Stop due to chain problem
Stopped due to fuse failure & gear box problem
PC 2 Stop due to coupling rubber damage
PC 3 Stop due to wheel track problem
Primary Sludge Pump PSP 1 Stop due to fuse burnt
Stop due to motor problem not able to pump the sludge
PSP 2 Stopped due to electrical problem
Primary bio-filter PBF 1 Not rotating due to less flow
PBF 2 Not rotating due to less flow
PBF 4 Stop due to arm box problem
26
Recirculation pumps RCP Stop due to repair of non return valve
Secondary bio-filter SBF2 Stop due to tie rod problem
SBF3 Stop due to less flow
Secondary Clarifier SC3 Stop due to roller wheel rubber breakdown
Secondary Sludge pump SSP 1 Stop due to bearing problem
Stop due to gland cup problem
SSP 2 Stop due to impeller problem
Other maintenance measures in the plant are as follows:
During heavy rains the bypass gate is opened by closing the gate valves of grit
chamber, clarifier and the water is allowed to the valley.
The units are cleaned for 3 days once in a year followed by painting of all units.
Regular lubrication, valves rotation, moving mechanical parts are checked and
replacement of worn parts is done.
Grit chambers, Clarifiers are cleaned when the moving arms give jerk, the water
during cleaning is diverted to standby unit and complete cleaning is done.
Oil levels and alignment of moving parts are checked regularly.
The flow is regularly diverted to standby units to ensure frequent use so as to
minimise load on working units and corrosion of standby units.
Pumps and motors are run in rotation basis for efficient use and high performance.
Screenings are manual removed continuously from the screens to avoid clogging.
Once a problem is reported, concerned personnel are intimated and corrective
measures are taken immediately.
3.5 Vrishabhavathi Valley (V-Valley) 60 MLD Tertiary Treatment Plant (TTP)
3.5.1 Purpose of the plant
Bangalore Water Supply and Sewerage Board (BWSSB) are having an 180MLD
secondary sewage treatment plant at Vrishabhavathi Valley, Mysore road. Bangalore city is
located 100km away and 0.5km above its only dependable source of drinking water, River
Cauvery. With high energy cost involved in pumping of water coupled with extremely finite
27
source of raw water and facing ever growing needs of an increasing population, BWSSB was
prompted to conserve potable water and to take a serious look at ventures in recycling and
reuse of wastewater. Hence, BWSSB decided to build a 60MLD tertiary wastewater
treatment plant to meet the demands of the proposed new power generation plant at Bidadi by
M/s Karnataka Power Corporation Limited and other plants near Bangalore city. This would
save usage of potable water in these industries which is a depleting source.
This project was implemented under ‘Improvement of Water Supply and Sewerage
System in Bangalore’ under INDO-FRENCH Protocol. BWSSB awarded this project to
Degremont Consortium consisting ONDEO Degremont SA, France and ONDEO Degremont
Limited India.
SECONDARY TREATED SEWAGE
28
PUMPING STATION
REPARTITION
TRICKLING FILTER A TRICKLING FILTER B
COAGULANT
DENSADEG DENSADEGPOLYMER
BELT PRESS FILTRATE WATER
Fig 3.14: Flow diagram of 60MLD Tertiary Wastewater Treatment Plant
3.5.2 Treatment scheme
The design of the plant is based on the following principles:
1. Since the plant is getting the effluent from the existing 180MLD secondary sewage
treatment plant, the plant is assured of a constant flow of 60MLD.
2. For the optimization of the design, cost and operation & maintenance, the plant is
constructed in two modules of 30MLD each.
3.6 Detailed Description of units
3.6.1 Trickling Filter
The pumped secondary treated sewage from the inlet pump house is split into two
modules of 30MLD each in a repartition chamber. This chamber is built at a higher elevation
so that further flow could be a gravity flow.
From the repartition chamber, the sewage flows into a trickling filter unit. The
hydraulic head differences between the sewage level in the repartition chamber and the holes
in the sprinkler mechanism is sufficient enough to rotate the hydraulically. In the trickling
29
PRE-AERATION TANKDIRTY WASH
WATER TANK
FLOPACFLOPAC
FLOPAC FLOPAC
FILTERED WATER TANK TREATED WATER RESERVOIR
filter, the sewage trickles from the top to the bottom through a plastic media, wherein BOD
level of the inlet sewage is reduced. The sewage is collected in a common trickling filter
outlet channel and is fed into DENSADEG clarifier.
Existing Trickling Filters in V-Valley TTP
Repartition chamber
Construction : Concrete
Length : 6.2 m
Width : 3.2 m
Liquid depth : 1.22 m
Tank depth : 1.92 m
Trickling filters
Construction : Concrete with hollow block masonry
Nos : 2
Shape : Orthogonal
Diameter : 20.4 m
Height : 7.36m
Sprinkler mechanism
Nos : 2
Size : 20.4m
Type : Hydraulic sprinkler
Trickling filter media
Nos : 2
Volume : 1620 m³ for each TF
Type : Cross pack 22
Trickling filter outlet penstock
Nos : 1 Type : Manual Size : 750 mm x 750 mm
3.6.2 High Rate Clarifier
It is based on the following five principles:
30
1. Coagulation in a mixing chamber equipped with a flash mixer, where ferric
chloride is added.
2. Flocculation in a reactor equipped with a turbine type flocculator and a tube
intended for rapid dispersion of the injected polymer.
3. Slow velocity transfer from the reactor to the settling zone to preserve floc
cohesion.
4. External recirculation of sludge from the thickening zone to the reactor.
5. Optimized lamellar settling.
The Densadeg is complemented by two chemical units (ferric chloride and polymer)
and a sludge dewatering unit. There are two no’s of Densadeg clarifiers in this plant and each
consist of two flash mixers, one flocculator, and one clarification unit containing scum pipe
and scrapper mechanism.
Operating principle
Flash mixer: The flash mixer receives a dose of ferric chloride as determined by jar
test in order to provide pre-coagulation before the sewage enters the flocculator.
Turbine reactor: One of the original features of the process is the physico-chemical
reaction such as crystal flocculation or precipitation or any other specific precipitation
reaction takes place in the reactor. The reactor is made up of two-series reactor, an agitated
reactor which performs rapid flocculation, and a plug-flow reactor where slow flocculation
takes place.
Agitated reactor: The raw water, which has been pre-coagulated in the flash mixer,
flows into the centre and the base of the reactor. An axial-flow turbine inside the duct
performs homogenous stirring of the reactor, provides the necessary energy and ensures
mixing of the polymer. Inside the agitated reactor, suspended solids concentration levels (floc
or precipitate) are optimized for the type of treatment by external recirculation of the
concentrated sludge from the thickening zone.
Plug-flow reactor: The upflow reactor serves for slow flocculation producing
enlarged floc. The innovative design of this reactor delivers a particularly dense and
homogenous floc of considerable size. As a result of floc densification, the flow enters the
settling zone at far greater speeds than in earlier systems.
31
Existing High Rate Clarifier (DENSADEG) in V-Valley TTP
Flash mixer chamber
Construction : Concrete
Length : 1.4 m
Breadth : 1.4 m
Depth : 3.575 m
Nos : 2
Volume : 5.8 m³
Flocculator
Construction : Concrete
Length : 5.15 m
Breadth : 5.15 m
Depth : 6 m
Nos : 1
Volume : 151 m³
Lamellar modules
No of sheets : (DH 1500*1000) - 632 and (DH 500*1000) - 158
Material : High compact polystyrene food grade
Colour : White
Width (1module) : 1 m
Inclined length : 1.5 m
Thickness of sheet : 1 mm
3.6.3 FLOPAC
The trapped suspended solids gradually block the interstices between the consistent
elements of the filtering media. This phenomenon is known as ‘filter clogging’. As the
clogging increases, the head loss increases which affects the flow of water. When head loss
has reached a figure close to 1.5m of water column, the filter must be cleaned. The rate of
clogging depends on turbidity in the water, settling process, and grain size of the media. The
FLOPAC has four units:
1. Pre aeration tank
32
2. Filters
3. Filtered water tank
4. Dirty wash water tank
Pre aeration tank: Pre aeration tank is provided with an air pipe network with
VIBRAIRS GM type air diffusers for the aeration of water. The air diffuser network supplies
the required amount of air with the help of a set of air blowers. The air blowers are installed
inside FLOPAC blower room. The blower is operated in required speed depending on the
required dissolved oxygen level. Dissolved oxygen meter is installed at the outlet of pre
aeration tank which helps in measuring dissolved oxygen.
Whenever the inlet parameter exceeds the design parameter, a post coagulation
system is provided to improve the efficiency of filtration. Characteristics of the filter are
detailed below.
1. A filtration process involving a thick layer of sand.
2. A large water depth, which provides suitable positive pressure in all parts of the filter.
3. An equal distribution among the filters of the total water flow to be filtered.
4. A simultaneous air and water backwashing followed by water rising, without
expansion of the filter bed. Cross wash ensures the discharge of dirty water of all
impurities by eliminating any zero horizontal total velocity area in which the detached
particles might be allowed to settle again.
Filtration: Water flows equally into all chambers running along the whole length of
the chamber. After filtration, water will be collected under the false floor and then moves to
filtered water outlet channel which is below the filter feed channel.
Washing: A simultaneous scour air backflow and filtered water backflow is followed
by a rinsing stage with filtered water. During washing, the air is distributed by the long-stem
nozzles and water. The frequency of washing cycle depends on the characteristics of water.
Washing is done when the head loss reaches 1.5m. The various sequences of filtration and
washing are as follows:
1. Lowering the water level to the upper edges of the wastewater outlet by sloping the
filtration and opening the wastewater outlet.
Duration : 1 minute
Air flow rate : 60 m³/hr/m²
33
2. Injecting air and water
Duration : 10-15 minutes
Air flow rate : 60 m³/hr/m²
Water flow rate : 10 m³/hr/m²
3. Rinsing with water until the water is discharged into the sewer
Duration : 10 minutes
Water flow rate : 20m³/hr/m²
Existing FLOPAC Units in V-Valley TTP
Pre aeration tank
Construction : Concrete
Length : 7.5 m
Width : 5.5 m
Liquid depth : 6.46 m
Tank depth : 7 m
Pre aeration blowers
Nos : 2
Capacity : 750/375 Nm³/hr
Pressure : 0.8 bar
FLOPAC filter design
Nominal input : 2500-2740 m³/hr
No of filters : 4
Length : 7.95 m
Width : 9.08 m
Unit filter bed area : 72 m²
Media depth : 1.5 m
Media type : Biolite
Wash water rate : 10 m³/m²/hr
Air scour rate : 60 m³/m²/hr
Backwash air blower
Nos : 2
Capacity : 5000Nm³/hr
34
Discharge pressure : 0.6bar
Dirty water tank
Construction : Concrete
Length : 27.16 m Width : 9.8 m Liquid depth : 3.69 m Tank depth : 4.19 m
Filtered water tank
Construction : Concrete
Length : 7.5 m
Width : 5.5 m
Liquid depth : 3.2 m
Tank Depth : 7.64 m
3.6.4 Sludge Treatment
The sludge extracted from the DENSADEG is stored in a sludge storage tank and then
sent by sludge feed pumps to the dewatering machine, Superpress after addition of an organic
polymer.
The polymer is prepared in the poly preparation tank and is feed into the flocculator
of Superpress through poly dosing pumps. The dewatered sludge is transported through
conveyor belts to the sludge lime mixer and the filtrate is collected into a filtrate sump and is
pumped to the flocculator of densadeg.
The superpress belts are washed with filtered water pumped from filtered water tank
through belt wash pumps at a pressure of about 8bars after passing through on-line strainer to
remove any particles, if any.
In the sludge lime mixer, the dewatered sludge is conditioned with quick lime for
increasing the pH up to 12 for stability over extended storage and dryness up to 25%.
SUPERPRESS Principle
The superpress is designed for the removal of most of the water contained in sludge
by continuous filtration, under pressure, of a layer of sludge placed between two filter belts
35
after appropriate chemical conditioning that promotes the formation of a bulky floc well
separated from the water. However, the principle of continuous pressure filtration has its
limits; in particular there is a risk of side flow of sludge under the effect of the pressure
applied.
Sludge flow as a function of:
Its rheological characteristics
The water content in the sludge at the inlet of the pressing zone.
Therefore, it is necessary to remove a great part of the water contained in the sludge
before applying the dewatering pressure.
The preliminary drainage phase is essential as it makes it possible to quickly obtain
thicker and much denser sludge than originally present thus increasing the pressing capacity.
The sludge should be evenly distributed over the entire width of the belt to optimize the
production capacity of the unit and the dry solids content of the cake produced.
SUPERPRESS Operation
The lower filter belt is defined as the one receiving the sludge from the flocculator
and the other filter belt is referred to as the upper belt. The sludge to which a polyelectrolyte
has been added is fed to a flocculator equipped with a vertical variable speed stirrer and flows
onto the first belt in the drainage zone. Here the sludge goes through two fences and is
distributed over the belt width by an equalizing roller. Sludge drainage is improved by the
furrowing effect of the fences and slight compacting by the roller help free drainage of the
sludge. After drainage, the sludge is squeezed between the two belts and undergoes
progressive compression in a wedge-shaped inlet and a large diameter perforated drainage
drum until it undergoes the final pressure determined by the degree of tensioning of the belts.
The two filter belts then run between a set of small-diameter return rollers that
increase the drainage pressure and at the same time exert shearing stress, which breaks up the
sludge structure, opens cake drainage grooves and improves final dewatering.
At the end of the line, the two belts part from one another after the drive roller and the
cake is removed by two scraper blades for discharge on the conveyor belt. Tracking of each
belt is automatically centred by a pneumatically controlled angular displacement roller. Both
36
belts are washed continuously by pressurized water sprayers in closed chambers. The filtrate
and wash water are discharged by gravity through launders.
Maximum performance of the filter for each type of sludge can be obtained through
simple settings:
Height of equalizing roller
Filter belt tensioning from pneumatic cylinders.
Belt drive speed adjustable through a manually controlled, mechanical, variable speed
drive.
Rotation speed of flocculator adjustable through a manually controlled, mechanical,
variable speed drive.
The fitter is fitted with fail-safe controls for immediate shutdown in the following cases:
Excessive belt over travel resulting from a malfunction in the tracking device.
Insufficient belt tensioning compressed air or wash water.
A manually operated emergency stop button.
Existing SUPERPRESS Units in V-Valley TTP
Sludge storage tank
Construction : Concrete
Length : 9 m
Width : 6.25 m
Depth : 4.06 m
No of tanks : 1
Volume : 200 m³
Sludge mixers : 2
Polymer dosing system
Construction : Concrete
Length : 1.95 m
Width : 1.7 m
Depth : 2.8 m
Volume : 8 m³
Polymer dose in tank : 1g/L
37
Dewatering machine
Nos : 2
Type : Twin belt pass filter
Width : 2 m
Supplier : Degremont
Belt conveyor
No : 1
Belt width : 0.5 m
Belt length :13.925 m
Speed : 0.5 m/s
Capacity : 1tonne/h
3.7 Plant Automation System
3.7.1 SCADA (Supervisory Control and Data Acquisitions)
The plant has been provided with Programmable Logic Controllers (PLC) based
control system for continuous operation and monitoring the plant. Operation of key unit
processes is totally automated like pulsators, filters, and sludge handling system. Plant can be
operated with little manual intervention.
Automation system consists of various instruments like flow measuring, level sensing,
Dissolved oxygen analysers, pressure sensing etc. There are three PLCs as mentioned above.
These PLCs are connected through three different networks that are as follows:
1. ETHWAY
2. FIPWAY
3. MODBUS
One number panel view operator station is installed at all control panels and filter
desks (LCPs). Telemechanique controllers at each location have been envisaged. The panel
view provides operator interface capabilities in saving space and flat panel designs. The
38
input/output modules are mounted in the I/O racks. The modular family of PLC and rack
based I/O consists of processor, I/Os and peripheral devices. This processor family delivers
power and flexibility with a wide range of communication configurations, features and
memory option. The inputs and outputs for the control system is handled by the following I/O
modules:
32-channel 24V Digital Input module
32-channel 24V DC Digital Output modules
8-channel Analog Input module
8-channel Analog Output Modules
The processor and I/O modules have LED type diagnostics indicating numbers.
3.7.2 Supervision system located in the Main Control Room (SCADA)
Operation
Start/stop from SCADA when switch on MCC is in ‘Auto’ mode indication
Indication on the screen ‘ON/TRIP’ for drives
All process events (levels, pressure, flow meter)
In case of the failure of supervision or the communication network, each PLC cabinet
continue to work with the last data transmitted. The operator can modify data when needed
directly on the operator interface in front of PLC cabinet. Operator is also informed of all the
process events through this operator interface (level, pressure, flow etc).
3.8 Maintenance of the Tertiary Treatment Plant
3.8.1 Mechanical Task Schedule
FLOPAC
Daily maintenance:
Oil level, vibration and noise check for belt wash pump, pre aeration air blowers,
backwash air blowers and air compressor.
Weekly maintenance:
Cleaning of equipment, stainer, and lubrication for belt wash pump.
39
Cleaning of equipment and lubrication for pre-aeration air blower, backwash air
blower air compressor.
Cleaning of equipment, filter and lubrication for EOT crane.
Monthly maintenance:
Check the alignment, tightness of all nuts, bolts for belt wash pump, pre-aeration air
blower and backwash air blower.
Check the alignment, belt tension, tightness of all nuts, bolts etc for air compressor.
Check all nuts, bolts, wire rope condition, limit switches, lubrication if required.
DENSADEG Clarifier
Daily maintenance
Check oil level of gear box, vibration and noise for flash mixer, flocculator and
scrapper mechanism.
Weekly maintenance
Cleaning of equipment and lubrication for flash mixer, flocculator, and scrapper
mechanism.
Monthly maintenance:
Check the alignment, tightness of all nuts and bolts; lubricate all bearing for flash
mixer, flocculator and scrapper mechanism.
Dewatering building
Daily maintenance:
Check oil level, vibration and noise for air compressor.
Check oil level, vibration and noise, and belt condition for Super press.
Check oil level, vibration and noise for screw conveyor, belt conveyor, flocculator
and booster pump.
Weekly maintenance:
Cleaning of equipment, belt tension, and filter for air compressor.
Flushing and operation of limit switches for Super press.
Cleaning of equipment, and lubrication for screw conveyor, belt conveyor and
flocculator.
Cleaning of equipment and stainer for booster pump.
Check the smooth operation of EOT crane.
40
Monthly maintenance:
Check the alignment of belt and tightness of all nuts bolts for air compressor, super
press, screw conveyor, belt conveyor, and flocculator.
Pipeline maintenance, tightness of all nuts, bolts for booster pump.
Check all nuts, bolts, wire rope condition, limit switches, lubrication if required.
CHAPTER 4.0
DISCUSSIONS
4.1 Recommendations
The screenings of raw sewage mainly consist of plastic materials which are
not supposed to be coming in sewage. The reason for this may be present due
to open channels that carry sewage to STP. Measure has to be taken to prevent
entry of such things into sewer channels.
The influent characteristics of raw sewage flow to STP vary widely, which has
direct …….on the quality of treatment.
The screens provided are efficient and efforts can be made to make them
100% efficient with adopting mechanical cleaning devices. The disposal of
screenings has to be done in an environmental friendly manner.
The breakdown of supporting arms in assembly in Primary clarifiers 2s has to
be replaced completely which reduces frequent repair charges.
Care has to be taken to avoid entry of the airborne wastes into clarifier and
bio-filters. Open channels can be covered with mesh to avoid such entry into
treated waters.
41
Bio-filters have to be replaced with new sprinkler mechanism (Rotary Arms)
for uniform and efficient distribution of wastewater on media. Proper
ventilation has to be made sure to overcome operational problems which lead
to lower efficiency.
The clearance between filter media and rotary arm over it should be not less
than 15 cm as per CPHHEO guild lines and proper alignment of rotary arm
can make sure of this parameter.
Recirculation of treated wastewater completely back into STP units during the
periods of lean flow helps efficient use of units and reduces load on receiving
valley, it is important to decrease load on valley so as to reclaim its naturally
stream quality.
Extension of laboratory facilities with advanced and required instruments is
necessary for regular analysis to check the performance of STP.
180 MLD STP is very old and obsolete technology hence authorities can think
of alternative/advanced methods of wastewater treatment , as in coming days
the load on plants will increase enormously there is a need for new, modified
and advanced treatment technique so as to curb the increasing pollution in the
natural valley stream.
Water reclamation and reuse goals can improve the conditions of valley which
has been polluted even though presence of sufficient treatment plants.
Stringent regulations by the authorities have to be laid before industries
around, to control the pollution through illegal discharges.
Institutional people are academics can be encouraged to know the best
possible treatment methods through research and projects helpful for
authorities.
42
References
G. Tchobanglous, F. Burton, (1991). “Wastewater Engineering, Treatment, Disposal and Reuse, 3rd edition, McGraw Hill Publications.
Joseph A. Salvato, Nelson L. Nemerow, Franklin J. Agardy, (2003). “EnvironmentalEngineering”, fifth edition, Published by John Wiley & Sons, Inc., Hoboken, New Jersey.
The expert committee, (1993), “Manual on Sewerage and Sewage Treatment”, second edition, Ministry of Urban Development, New Delhi.
http://www.wikipedia.org/Sewage_treatment.html
43
COD mg/l
44
DateFlow MLD Temperature 0 C pH
DO mg/l
Inlet Intermediate Outlet Inlet Intermediate Outlet Inlet1/6/2010 61 28 24 24 7.7 7.2 7.3 0.62/6/2010 63 27 24 24 7 7.1 7.3 0.33/6/2010 69 28 24 24 7.2 7.3 7.4 0.74/6/2010 68 27 24 24 7.2 7.2 7.3 0.55/6/2010 61 28 25 24 6.9 7.1 7.3 0.36/6/2010 62 27 24 25 7 7.3 7.4 07/6/2010 77 28 24 24 7.1 7.1 7.2 08/6/2010 77 27 25 25 6.9 7.2 7.3 09/6/2010 77 28 24 23 7 7.1 7.2 0
10/6/2010 67 27 24 23 6.9 7.3 7.3 011/6/2010 64 28 24 23 7 7 7.2 012/6/2010 60 27 25 23 7.2 7.1 7.3 0.313/6/2010 54 28 24 24 7.1 7 7.4 0.614/6/2010 51 27 26 24 6.9 7.2 7.3 0.515/6/2010 54 27 25 24 7.1 7 7.3 0.916/6/2010 47 27 25 24 6.9 7.2 7.5 0.817/6/2010 74 28 24 23 7.1 7.1 7.4 0.318/6/2010 90 27 24 24 7.2 7.3 7.2 0.719/6/2010 71 28 25 25 7.1 7.3 7.3 0.320/6/2010 66 27 25 25 6.9 7.2 7.2 0.521/6/2010 66 29 26 24 7 7.1 7.4 0.622/6/2010 66 28 23 22 6.9 7.2 7.3 0.823/6/2010 66 27 24 24 7.1 7.1 7.4 0.224/6/2010 72 29 25 24 7 7.3 7.4 0.325/6/2010 83 28 25 24 7.1 7.2 7.4 0.526/6/2010 81 28 25 24 7.1 7.3 7.4 0.627/6/2010 75 27 24 24 7.2 7.3 7.4 0.728/6/2010 73 28 25 24 6.9 7.3 7.4 0.629/6/2010 78 27 24 23 7.1 7.1 7.3 0.830/6/2010 81 27 24 24 7 7.3 7.5 0.31/7/2010 66 27 24 24 6.9 7.2 7.3 0.72/7/2010 66 28 25 24 7 7 7.2 0.33/7/2010 66 27 26 24 6.9 7.1 7.3 0.54/7/2010 72 28 26 24 7 7 7.3 0.65/7/2010 83 27 26 25 7.2 7.2 7.4 0.86/7/2010 81 29 25 25 7.1 7.3 7.6 07/7/2010 75 28 24 24 6.9 7.2 7.4 08/7/2010 73 27 24 23 7.1 7.1 7.3 0.19/7/2010 78 29 24 24 6.9 7.3 7.5 0
10/7/2010 90 28 24 24 7.1 7.3 7.4 0.211/7/2010 72 27 24 24 7.2 7.3 7.5 0.312/7/2010 83 27 25 25 7.1 7.2 7.4 0.5
Date
Inlet Intermediate Reduction % OutletReduction %
1/6/2010 738 286 61 176 762/6/2010 628 248 61 148 763/6/2010 714 239 67 168 774/6/2010 688 214 69 137 805/6/2010 714 258 64 181 756/6/2010 781 286 63 266 657/6/2010 681 246 64 210 698/6/2010 721 278 61 236 679/6/2010 664 241 63 173 74
10/6/2010 778 287 63 189 7611/6/2010 681 237 65 108 8412/6/2010 704 256 64 126 8213/6/2010 653 194 70 106 8414/6/2010 578 186 68 91 8415/6/2010 667 249 63 140 7916/6/2010 714 263 63 161 7717/6/2010 768 281 63 172 7518/6/2010 781 276 65 168 7819/6/2010 678 238 64 141 7920/6/2010 738 256 65 176 7621/6/2010 761 281 63 189 7522/6/2010 681 244 64 138 8023/6/2010 721 230 68 161 7824/6/2010 814 281 65 190 7725/6/2010 781 273 65 181 7626/6/2010 714 241 66 148 7927/6/2010 781 286 65 168 7928/6/2010 681 246 64 138 8029/6/2010 721 278 65 161 6730/6/2010 664 241 63 173 741/7/2010 778 287 64 189 762/7/2010 681 238 64 108 843/7/2010 704 256 68 126 824/7/2010 653 281 65 106 845/7/2010 578 244 65 91 846/7/2010 667 230 63 176 857/7/2010 768 281 63 176 758/7/2010 781 286 65 181 789/7/2010 678 246 64 141 79
10/7/2010 714 230 66 148 7911/7/2010 721 278 68 161 7812/7/2010 664 241 63 173 79
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Date SS mg/l Inlet Intermediate Reduction % Outlet Reduction %
1/6/2010 608 121 80 58 902/6/2010 437 107 76 49 893/6/2010 481 108 78 52 894/6/2010 518 119 77 58 885/6/2010 524 120 77 62 886/6/2010 558 116 79 110 807/6/2010 574 121 79 126 788/6/2010 536 110 79 116 789/6/2010 428 95 78 96 7810/6/201
0 573 113 75 74 8711/6/201
0 431 109 75 53 8812/6/201
0 478 98 79 59 8813/6/201
0 502 102 80 60 8914/6/201
0 436 92 79 47 8915/6/201
0 482 108 78 47 8916/6/201
0 510 104 80 51 8917/6/201
0 568 118 79 54 8918/6/201
0 537 107 80 58 9019/6/201
0 487 98 79 53 9020/6/201
0 581 108 81 54 9021/6/201
0 610 136 78 63 8922/6/201
0 571 116 80 58 8923/6/201
0 538 108 80 56 9024/6/201
0 622 123 80 62 9025/6/201
0 639 118 81 67 8926/6/201
0 571 108 81 52 9127/6/201
0 621 102 83 60 9028/6/201
0 600 98 84 50 92
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29/6/2010 510 112 78 48 91
30/6/2010 438 96 78 44 90
1/7/2010 589 100 83 46 922/7/2010 639 134 79 65 903/7/2010 571 115 80 60 894/7/2010 449 108 76 59 875/7/2010 426 103 76 55 876/7/2010 538 111 79 50 917/7/2010 539 99 82 47 918/7/2010 555 98 82 52 919/7/2010 488 91 81 69 8610/7/201
0 512 112 78 50 9011/7/201
0 469 111 76 49 9012/7/201
0 499 110 78 56 89
Date BOD3 mg/l
Inlet IntermediateReduction % Outlet Reduction %
1/6/2010 389 124 68 49 872/6/2010 362 109 70 47 883/6/2010 338 107 68 42 854/6/2010 372 118 68 57 865/6/2010 336 106 68 48 846/6/2010 356 141 60 54 707/6/2010 341 179 48 102 638/6/2010 378 188 50 139 699/6/2010 310 160 48 97 76
10/6/2010 336 106 68 79 8511/6/2010 326 94 48 48 8512/6/2010 342 106 50 52 8713/6/2010 321 93 48 46 8614/6/2010 310 98 68 42 8615/6/2010 339 106 71 47 8616/6/2010 356 119 68 55 8417/6/2010 379 128 71 62 8418/6/2010 346 110 68 58 8319/6/2010 321 106 69 51 8420/6/2010 371 118 68 56 8521/6/2010 410 127 69 63 8522/6/2010 341 118 65 54 8423/6/2010 381 113 70 51 87
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24/6/2010 357 109 69 46 8725/6/2010 389 121 69 62 8426/6/2010 378 103 73 48 8727/6/2010 356 128 64 49 8628/6/2010 341 108 68 55 8429/6/2010 321 106 67 53 8330/6/2010 312 101 68 68 781/7/2010 356 109 69 41 882/7/2010 399 122 69 43 893/7/2010 356 119 67 59 834/7/2010 358 110 69 47 875/7/2010 346 109 68 42 886/7/2010 325 107 67 57 827/7/2010 390 140 64 102 748/7/2010 366 123 66 49 879/7/2010 348 110 68 62 82
10/7/2010 331 105 68 51 8511/7/2010 369 141 62 102 7212/7/2010 356 107 70 51 86
The analysis results and flow data collected from the plant for the month June-July is presented in the tables above.
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