RAHUL PROJECT

Performance Evaluation of WTP at Gadchiroli

INTRODUCTION

1.1 General Safe drinking water is a basic need of all humans. To protect the human health, community water supply must be reliable, adequate of assured quality and readily accessible to all segments of the consumers. In India as well as in many countries, the expected level of progress in providing one of the most basic services to the people viz. safe and affordable drinking water and sanitation have not yet been achieved. The current practices of water purification are seldom adequate to produce secured water supply. It is essential to develop various tools to improve water purification and distribution system to achieve the goal of providing safe drinking water. A very large demand of civic amenities which have to keep with increasing demand of rising population. Therefore, identification of source of water supply its conservation and optimum utilization is of almost importance. Even the present scale of water supply to urban and rural population is grossly inadequate and not all communities are provided with safe water supply. In old day, population was very thin and also in the absence of industrial and agricultural development, a little amount of waste used to be disposed in water bodies. Water resources have maintained quality of natural self-cleaning mechanism. Today the human activity causes pollution and contamination of river and lake water, sea water, ground water and even treated piped drinking water, which is challengeable. The objective of present study was to evaluate the performance of the water treatment Plant at Gadchiroli District to focus the attention operation and maintenance agency of plant on gaps and deficiencies in operation and maintenance, if any and to suggest practical measure for possible improvement. To implement performance assessment, it is necessary to develop adequate and representative performance indicators. Good performance indicators can specify the measurable evidence that is necessary to document the achievement of a goal. To provide the higher quality and stable water to the customers, the water utilities themselves should establish the proper maintenance and management programs to enhance the availability of plant facilities and equipments in the water treatment plant. The aim of this research work is to set up the performance evaluation system for the Gadchiroli water treatment plant.

Performance Evaluation of WTP at Gadchiroli

1.2 Water Supply Development in India The development of public water supply in India actually belongs to the postindependence era prior to independence, the progress in the fields of urban and rural water supply was sporadic and slow and depended on the needs and priorites of the alien rulers. After independence, an extensive programme was embarked upon to meet the necessity of providing the bare requirements water in the rural areas. The Environmental Hygience Committee appointed by the Union Govt. providing water supply and sanitation facilities for 90 percent of our population within a span of 40 years. The National Water Supply and Sanitation Programme was formally launched by the Govt. in 1954. Under the programme, long-term interest loans for Urban Water Supply Schemes were sanctioned. For rural schemes Central and state Governments grant-in-aid was made upto 75 percent of the cost of schemes, the balance to be made by beneficiaries. Inverstments in public water supply and sewerage schemes have steadily increased with each plan period. Beginning with the First Five Year Plan (1951-56), when a total provision of Rs. 12 crores for outlay in the Fourth Plan (1969-70) increased to Rs. 409 crores of which Rs. 125 crores were earmarked for rural water supply schemes alone. However, it has to be pointed out that in spite of the increasing rate of provisions on the national urban and rural water supply and sanitation programmers, we have up till now been able to provide safe water supply to 5 percent of our villages and water supply with water-borne sewerage system to 30 percent of urban population. This shows that the quantum of efforts and investments made on these programmers are inadequate and we need to considerably accelerate the pace of the development of our public health engineering programmers in order to provide the entire community with means of protected or safe water supply and sanitation.

1.3 Status of Water treatment plants in India India accounts for 2.45% of land area and 4% of water resources of the world but represents 16% of the world population. With the present population growth-rate (1.9 per cent per year), the population is expected to cross the 1.5 billion mark by 2050. The Planning Commission, Government of India has estimated the water demand increase from 710 BCM (Billion Cubic Meters) in 2010 to almost 1180 BCM in 2050 with domestic and industrial water consumption expected to increase almost 2.5 times. The trend of urbanization in India is exerting stress on civic authorities to provide basic requirement such as safe drinking water, sanitation and infrastructure.

Performance Evaluation of WTP at Gadchiroli The rapid growth of population has exerted the portable water demand, which requires exploration of raw water sources, developing treatment and distribution systems. The raw water quality available in India varies significantly, resulting in modifications to the conventional water

treatment

scheme

consisting of

aeration,

chemical

coagulation,

flocculation,

sedimentation, filtration and disinfection. The backwash water and sludge generation from water treatment plants are of environment concern in terms of disposal. Therefore, optimization of chemical dosing and filter runs carries importance to reduce the rejects from the water treatment plants. Also there is a need to study the water treatment plants for their operational status and to explore the best feasible mechanism to ensure proper drinking water production with least possible rejects and its management. With this backdrop, the Central Pollution Control Board (CPCB), studied water treatment plants located across the country, for prevailing raw water quality, water treatment technologies, operational practices, chemical consumption and rejects management. The collected information was processed & broad observations on various treatment plants are as follows. 

At many water treatment plants, the raw water is very clean having turbidity less than 10

NTU during non-monsoon period. Whenever the turbidity is so low, alum or Poly Aluminium Chloride (PAC) is not added, although the water passes through all the units such as flocculators and settling tanks before passing through rapid sand filters. 

Alum is being added as coagulant in almost all Water Treatment Plants, however,

recently water treatment plant at Nasik and Pune have started using PAC instead of alum, which is in liquid form. The water treatment plant personal appeared to prefer PAC as no solution is to be prepared, as in case of alum. Bhandup water treatment complex, Mumbai is using aluminium ferric sulphate, which is one of the biggest water treatment plant in India. 

In few plants, non mechanical devices such as hydraulic jumps are being used for mixing

of chemicals. Also, paddles of flash mixer were non functional in some water treatment plants. 

Some of the water treatment plants are using bleaching powder for chlorination, while

majority are using liquid chlorine. The operation and maintenance of chlorinator was far from satisfactory and chlorine dosing is often on approximation. Instrumentation part in terms of chemical addition and chlorination appeared to be imperfect in most of the plants. 

Some water treatment plants were using alum bricks directly instead of making alum

solution before addition.

Performance Evaluation of WTP at Gadchiroli •

In few plants, tapered flocculation units with flocculator of varying speeds are in use. In

this case the settling tanks are rectangular with hopper bottom. These tanks do not have mechanical scraping arrangement and are cleaned during the period of filter backwash. •

Pre-chlorination dose, in case of Agra water treatment plant was reported to be high as 60

mg/l, which is a matter of great concern for water treatment plant authorities. This is because raw water BOD is very high due to discharge of industrial effluents on the upstream side of water treatment plant intake. •

All the water treatment plants (except defluoridation plants) have rapid sand filters. In

addition to rapid sand filters, slow sand filters were in operation at Aish Bagh, Lucknow and Dhalli, Shimla. At Nasik, water treatment plant had dual media filter using coconut shell as second medium, which is being replaced by sand. •

Filter runs are generally longer about 36 to 48 Hrs. during non-monsoon period except

Sikandara WTP, Agra where filter runs are shorter during this period due to algae problem all though rapid sand filters are located in a filter house. This is due to high pollution (BOD) of raw water. Normally, wherever rapid sand filters are located in filter house, algae problem is not encountered. Some of water treatment plants, where rapid sand filters are in open, algae problem is overcome by regular cleaning of filter walls or pre-chlorination. •

Mostly, filter backwash waters & sludge from water treatment plants are being

discharged into nearby drains, which ultimately meet the water source on downstream side of intake. However, exception is at Sikandara water treatment plants, Agra, where sludge and filter back wash waters are discharged on upstream side of water intake in Yamuna River. •

In some of the water treatment plants, clarifiers are cleaned once in a year and the sludge

are disposed off on nearby open lands. AT Haiderpur Water Works in Delhi, reuse of sludge and filter back wash water is under consideration. In case of Dew Dharam water treatment plant at Indore and Narayangiri water treatment plant at Bhopal, the backwash water is being sused for gardening, while at Balaganj water treatment plant, Lucknow, filter backwash water is recycled by way of sedimentation and feeding them at inlet of water treatment plant. •

In many cases, details of water treatment plant units such as their sizes, specifications,

layout etc are not available. This is possibly because of water treatment plant executing agency and water supply system operation & maintenance agency are different. Water treatment plant operation manual were also not available at many plants.

Performance Evaluation of WTP at Gadchiroli •

In most of the cases, adequacy of water treatment from health point of view is ensured by

maintaining residual chlorine of 0.2 to 0.1 mg/l at the farthest point of distribution system. Very few water treatment plants have facilities for MPN testing. •

Water treatment plants are either operated or maintained by Public Health Engineering

Departments or local municipal corporations. At Shimla, water treatment plant is under Irrigation and Public Health (IPH) of the Himachal State Government, whereas water distribution is looked after by Shimla Municipal Corporation. •

Operation and maintenance of Sikandara, Agra Red Hills, Chennai, Peddapur,

Hyderabad, Kotarpur, Ahmedabad etc. water treatment plants have been assigned to the private organizations. In Uttar Pradesh, execution of water treatment plant is carried out by UP Jal Nigam and operation & maintenance is carried out by UP Jal Sansthan, not by local municipalities. •

Okhla water works, Delhi gets raw water from rainy well and is subjected to ozonation

and denitrification. Operation and maintenance of ozonators and denitrification plant is being looked after by a private organization. It has been learned that ozonation is being carried out principally for iron removal and not for disinfection. •

Typical problem of excess manganese is faced at Kolar water treatment plant, Bhopal

during May to October. This problem is being tackled by adding KMNO4 and lime at the inlet. In Surat, at Katargam water works, raw water is coloured. The treatment plant is having proper O & M, could remove colour. 

Mundali water treatment plant at Bhubaneswar has a capacity to treat 115 MLD, but in

practical operated for 1 shift to treat 40 MLD water. Whereas, Palasuni water works at Bhubaneshwar is having capacity of 81.8 MLD, but plants are overloaded to a total of 106.5 MLD. •

Kotarpur water treatment plant located at Ahmedabad has a capacity of 600 MLD, but

treating only 300 MLD, due to shortage of raw water. •

State of art water treatment plant exists at T.K. Halli, Bangalore, which has all the

operation computerized. This plant has pulsator type clarifiers and plant authorities appeared to be worried about excess chemical consumption and dilute sludge from these clarifiers. At this plant, clarifier sludge is being conditioned with polyelectrolyte and dewatered by vacuum filters.

Performance Evaluation of WTP at Gadchiroli Filter backwash waters are discharged into the nearby drain. The distance of Water treatment plant is more than 80 kms from Bangalore city. Looking at the distance, it may be appropriate to have chlorination facility near to the city and near the point from where distribution starts.

1.4 Status of Water Supply in Maharashtra State As per the constitution of India, taking care of the water supply and sanitation needs of the citizens is a responsibility of State Governments and its of governance such as the Zilla Parishad, Urban Local bodies and to some extent the Gram Panchayats also. In Maharashtra, the Ministry of Water Supply and Sanitation along with the department of Water Supply and Sanitation was created in 1996 to exclusively concentrate on the poor coverage and access to these essential services in both urban and rural areas. The Ministry is responsible for setting the policies for the State in this sector and coordinate with the Central Government and other key institutions. The Ministry is headed by the Minister of Water Supply and Sanitation and is supported by the State Minister for Water Supply and Sanitation. The Secretary heads the Water Supply and Sanitation Department (WSSD). It is planned to allocate funding of Rs. 438 Crore to be spend in next four years to achieve goals related to providing safe drinking water to the community. The rural water supply scheme in the state has been planned considering growth of about 2.5% in state population. (Present population of Maharashtra in about 9.6 crore) The Minister of Urban Affairs of the Government of India, formed in 1985, was set up to review State development plans, and influences the policies and practices of the Urban Water Supply and sewarege Sector. The Planning Commission also has a special cell that advises on the sector policy. Central water Commission conducts hydrological observations in Wainganga basin at 21 Stations. These sites are maintained under Key Hydrological Stations. Out of these 21 sites, water quality is monitored at 9 sites. Central Water Commission has been monitoring the water quality of Wainganga river for more than 30 years. The various water quality parameters such as Physical, Chemical, Bacteriological, Trace & Toxic metals and Pesticides are observed at these sites. The data for core parameters viz. pH, Electrical Conductivity (EC), Biochemical Oxygen -

-

Demand (BOD), Dissolve oxygen (DO), Nitrate (NO3 ), Nitrite (NO2 ), Total Coliform (Tcol) and Faecal Coliform (Fcol) are considered for the year 2005-06 to 2009-10 at these nine locations in the basin to study the water quality board.

Performance Evaluation of WTP at Gadchiroli

1.5 WATER TREATMENT TECHNOLOGIES Three basic purpose of Water Treatment Plant are as follows I.

To produce water that is safe for human consumption

II. To produce water that is appealing to the consumer III. To produce water - using facilities which can be constructed and operated at a reasonable cost. Production of biologically and chemically safe water is the primary goal in the design of water treatment plants; anything less is unacceptable. A properly designed plant is not only a requirement to guarantee safe drinking water, but also skillful and alert plant operation and attention to the sanitary requirements of the source of supply and the distribution system are equally important. The second basic objective of water treatment is the production of water that is appealing to the consumer. Ideally, appealing water is one that is clear and colorless, pleasant to the taste, odorless, and cool. It is none staining, neither corrosive nor scale forming, and reasonably soft. The consumer is principally interested in the quality of water delivered at the tap, not the quality at the treatment plant. Therefore, water utility operations should be such that quality is not impaired during transmission, storage and distribution to the consumer. Storage and distribution system should be designed and operated to prevent biological growths, corrosion, and contamination by cross-connections. In the design and operation of both treatment plant and distribution system, the control point for the determination of water quality should be the customer’s tap. The third basic objective of water treatment is that water treatment may be accomplished using facilities with reasonable capital and operating costs. Various alternatives in plant design should be evaluated for production of cost effective quality water. Alternative plant designs developed should be based upon sound engineering principles and flexible to future conditions, emergency situations, operating personnel capabilities and future expansion.

Performance Evaluation of WTP at Gadchiroli

1.6 Water treatment Plant at Gadchiroli The city of Gadchiroli located in the border of Maharastra & Chhattisgad State. Present population of Gadchiroli city is 53,800. Water supply to the city is being arranged from Wainganga river (Bormada Ghat). The capacity of Water treatment plant is 12.5 MLD, which is double to required for present population. The Water treatment plant scheme was sanctioned in 1996 to 1997. The water treatment plant was constructed in the year 10/8/2003. The source of water is Bormada Ghat of Wainganga river which is at 3 km from 0 mile stone of the Gadchiroli city. The Wainganga river is having 250 meter wide basin. All water supply to the Gadchiroli city is being catered by this plant. The plant is running for 8+8=16 Hours into two shifts. Though the plant is designed for 12.5 MLD but only 6 MLD of water is being treated & supplied to the city. The design and construction of the plant is conventional one the various units being aeration fountain, flash mixer, clariflucculators, rapid sand filters, chemical house, Clear water sump and pump house.

1.7 Scope of Work Performance of the water treatment plant is an essential parameter to be monitored and evaluated to better understanding of design and operating difficulties in water treatment plants. The conclusions of these evaluations may determine required recommendations and highlight modifications requirements for continuous design and operation scheme. It was decided to evaluate the performance of the plant at Gadchiroli . The work includes measurement of pH, Total Solids, Suspended Solids, Residual Chlorides, Turbidity, Flow, D.0 of water at various stages of treatment, such as inlet and outlet, of cascade aerator, filter and chlorinated water. The scope of work comprised mainly the following. 

Collection of engineering and design detail of the plant and discussion with plant staff.



Visit to the plant for sampling and analysis with a view to study the characteristics of raw and treated water and performance of treatment units at various stages of treatment.



Performance Evaluation with respect to operation and maintenance of the plant including plant safety.



Providing practical recommendation to improve the performance of the water plant.

Performance Evaluation of WTP at Gadchiroli

Fig. 1.1 Image of Gadchiroli water treatment plant

Performance Evaluation of WTP at Gadchiroli

LETERATURE REVIEW 2.1 General From the public health point of view, it is necessary that all water supplies must be invariably free from all types of impurities whether suspended or dissolved in water and no untoward risk should occur to the health of the public as a result of any water contamination. When the surface waters as from rivers or lakes were used, the method employed was to let such waters remain undisturbed or quiescent for some time till all the turbid suspended particles settled down and clear potable water drawn off from upper layers. This led to the construction of impounding reservoirs. The next development in the purification methods was through the process of Filtration i.e., allowing water to pass through beds of which could not be removed earlier were caused to be removed. It was found that the process of filtration was greatly accelerated if waters were pretreated with certain substances which when added formed large masses of precipitates or flocs out of the impurities present and which in the process settled down and were ultimately removed. The water pre-treatment process is now called Coagulation, but this process was equally known to the ancients who used solutions of certain vegetable called nirmali. Nowadays, alum is chiefly used for this purpose. The water having undergone through filtration was still found to contain minutely-sized living organisms as were apparently not visible to the naked eye. These were later found to be responsible for breeding germs causing diseases like cholera, typhoid, dysentery etc. In order, therefore, to thoroughly ensure protected supplies devoid of any health hazard, it was found necessary to remove these organisms by disinfecting water through the process of adding chlorine or chlorinous compounds to water i.e., chlorination. Other methods of disinfecting water viz., treatment through ozone or ultra-violet rays or excess-lime are also in use nowadays, but in the treatment of large public water supplies, we still stick to chlorination, being the most effective of all. Thus, it may be seen of what great importance, a public water supply or waterworks system has to be both from the point of view of providing an adequate and reliable supply of water catering to all the public needs and also ensuring that the supplies so made are not only potable but are fully protected against every infection which might otherwise pollute water and cause epidemics resulting in untold human sufferings and sufferings and loss.

Performance Evaluation of WTP at Gadchiroli The various physio-chemical and bacteriological parameters which concerns with healths are needed to study, so an effort is done by following studies. Baroniya Mamata, Baroniya Sanjay Singh, Jain Monica (2012) This paper highlights the Characteristics of raw water were obtained from BNP water treatment plant.In this the primary parameters concern with turbidity. The level of pollution is not too high that its use as raw water source is not a major issue of concern. The raw water quality at this location may be considered suitable in respect of ability of treatment plants to produce good quality treated water. The water treatment plant at BNP campus, Dewas, India revealed that a set pattern of operation and maintenance is being followed due to which it continues to fulfil the requirement of the people. The alum dose ranges from 30-80 mg/l and the dosing equipments were also found satisfactory. Algae growth was not significant in the filters. However, in open filters, frequent cleaning of filter bed walls is required. Use of ozone, potassium permanganate, copper sulphate etc., may be explored through research and development activity for algae problem or any other contamination of water source. Regular training to the plant operators for proper functioning of the system is suggested. Efficient MIS (Management information system) should also be developed to cater to all the activities of the plant.

M.A. EIDib, Mahmod A. AzeemEIDayoumy (2003) The findings of this research may be applicable for other WTP either under design or under operation. The finding of investing of the treatment plant in Dakahlia (Meet Fares). The research conducted in this topic was carried out by observing the engineering design to assure matching of standards and codes. The biological and bacteriological analysis was conducted to investigate water quality. The results drawn in this paper outlines comes with the importance of accurate engineering design and need for continuous and analysis of each unit performance regularly.

E.E. Chang , Chiang Peng-Chi, Huang Shu-Mei (2007) This paper highlights performance evaluation systems for the water production department in the Taipei Water treatment plant which were developed throughout this

Performance Evaluation of WTP at Gadchiroli investigation. To achieve high quality and stable water to customer, the water utility themselves should be establish the proper maintenance program, to enhance the availability of planned facilities and equipment. Water production cost and removal efficiency are developed and analyzed to draw out an implementation plan for optimizing the performance of the Taipei water treatment plant.

In

addition, establishing a regular performance evaluation system to identify

potential and existing problems so that correction action could be immediately taken, developing a sound database program, and cooperating with the stakeholders for source water protection are the major tasks that should be implemented to achieve the objectives of safe drinking water and clean water.

R. S. Dhaneshwar, V. P. Sharma, R. K. Gupta, P. S. Kelkar and R. Paramasivam (1991) The supply water work with single hand to enhance the problem of supplying adequate quantity of potable water to the public. This paper highlights the performance of various plant units, the status of operation and maintenance plant feature with laboratory facilities of overall management of water at Varanasi, Lucknow, Agra, Kanpur, and Nainital in Uttar Pradesh.

S.B. Parjane, M.G. Sane (2011) This paper highlights the finding for performance of Grey water treatment plant & laboratory scale system. The evaluation conducted for three seasons & research work carried out by reviewing the other treatment plant to assure matching of standards & codes. The results presented in this study establish the potential applicability of the developed methodology. This laboratory scale grey water treatment plant is a combination of natural and physical operations such as settling with cascaded water flow, aeration, agitation and filtration, hence called as hybrid treatment process. All the natural and easily available low cost materials were used for the treatment process.

S. J. Kardile, S. K. Gajendragadkar (1993) This paper highlights the evaluation of the performance of water Treatment Plant in Trimbakeshwar, Nasik during the monsoon of the year 1991. Today most of the surface water are treated in adequate amount irrespective of drinking water. Mostly in recent years, there are the awareness of clean drinking water in small towns & villages. Actually most of conventional facilities has limitations, that’s why most of world engineers are trying their best to improve this condition. .

Performance Evaluation of WTP at Gadchiroli

2.2 Theory of Water Treatment Plant 2.2.1 Description of Gadchiroli W.T.P. The Gadchiroli Water Treatment Plant is located just adjacent to Bormada Village on west side of Gachiroli City. This plant is 3 Km from zero mile stone of Gadchiroli. The Longitude is 79o57’24’ and Latitude is 18o57’06’ the plant supply water to Gadchiroli city. The plant is located on an elevation land track at a high level from road and nearby area. The present capacity of the plant is 12.5 MLD, which can provide water to about 1.5 lakh peoples, Where as the present population is only 53,800. The plant is constructed in RCC frame structure in 2001 & commencement of WTP is in 10/8/2003. It was run for 6 month by Maharashtra Jivan Pradhikaran Department & hand over to the municipal council of Gadchiroli. The plant includes Intake well, Pump house, Rising main, Stilling chamber, Measuring channel, Flash mixer, three Clarifloucculator, 4 Rapid sand filter, Chemical house with alum storage room, chlorine room & water sump etc. The scheme of WTP at Gadchiroli was sanctioned in 1997. The work of WTP construction was over in 2002. It is design for 12.5 MLD but working on 6 MLD. The estimated cost was about 12 cores. The area of land is 5.42 acres. The population was 42,469 in year 2001 & now in year 2011 is 53,800. The design rate of supply is 33.50 LPCD. The source of supply is Bormada Ghat of Wainganga river which is perennial in nature & which is 2 km from Bormada Village. The water from intake to water treatment plant convey through 560 mm diameter pipe.

Fig.2.1 Layout of water treatment plant of Gadchiroli

Performance Evaluation of WTP at Gadchiroli

2.2.2 River as a Source of supply The water received from precipitation i.e. rain or melted snow is the surface water which flows in the form of rivers, streams, lakes and ponds. In India, many cities like Delhi, Calcutta and Ahmadabad derive their water supply from rivers. The principal advantage of river as a source of water supply is the large quantity of water available for supply throughout the year. However, since water has to travel a long distance from the source located in mountains where it is fairly pure to the towns in plains, its quality deteriorates as river more or less serves as a natural drain for all discharges from the region. Though river water may be softer than ground water, it contains large amount of organic matter. Besides, it picks up lot of suspended matter, clay, silt etc. and becomes muddy in appearance. Being easily accessible, rivers are freely used for washing, bathing etc. In India, it is usual for dead bodies to be burnt on the banks of rivers. Besides, places of pilgrimage are normally situated of water as a source of water supply. Pollution may also be caused by discharges of trade effluents from industries. It is, therefore, necessary that river water should be thoroughly treated and protected before it can be made as a source of water supply for towns.

2.2.3 Quality of surface water Impurities in water normally are of two types, suspended and dissolved. The surface waters are characterized by the suspended impurities whereas the ground waters are generally free from the suspended matter but are likely to contain a large amount of the dissolved impurities, which they gather during the course of their travel in the underground strata comprising rocks and minerals. The suspended matter often contains the pathogenic or diseaseproducing bacteria; as such surface waters are not considered to be safe for water supply without the necessary treatment. Ground waters are comparatively safer and fit for use with or without minor treatment only. The rain water is soft, has a flat taste and is free from contamination. As however, rain falls through the air, it collects dusts and gases from atmosphere and becomes impure. Where rain water is collected in storage tanks, it may pick up impurities and is therefore required to be disinfected before use for drinking. However, because of the soft nature of the water, it finds an excellent use for washing purposes. The river water varies in quality. The variation is caused by the great difference in the maximum and minimum flow. The maximum flow is caused by high floods, resulting in an increase in turbidity and bacteria due to the surface wash brought into the river. The minimum

Performance Evaluation of WTP at Gadchiroli flow is due to the flow of ground water into the river, resulting in the decrease of turbidity but increase of dissolved impurities. The river water is also usually found to be contaminated with sewage or industrial waters from towns and cities.

The river water, therefore, must be

thoroughly treated before supplying for public use.

2.2.4 Impurities in Water and their Importance Impurities in water may be classified as follows (a) Physical Impurities. (b) Chemical Impurities. (c) Bacteriological Impurities. The physical impurities give taste, odour, colour and turbidity. Taste and odour may be caused due to the presence in water of organic matter dissolved during passage through the ground or from industrial wastes or due to micro-organism such as algal growth. Turbidity is caused by the suspended and colloidal matter while colour may be due to the presence of mineralogical compounds such as iron oxide etc. Physical impurities do not have a direct relationship with health but produce many indirect consequences. Turbid water may protect pathogens (disease-producing micro-organisms) from the effects of chlorination and it may contain mineral matters that irritate stomach lining. It is often observed that a safe water supply that has a disafgreeble taste and odour is likely to be passed up by people for unsafe water that looks and tastes good. The chemical impurities may be either inorganic or organic. The bacteriological impurities are caused by the presence in water of the pathogenic or disease-producing type of bacteria making water dangerous for human consumption and health. From the public health point of view, therefore, bacteriological impurities are the most important. The pathogenic bacteria are generally inherent in the coliaerogenous or Coliform group of bacteria of which the Bacillus coliformerly known as B coli (and now called the Escherichia coli or E coli) is important. The E coil bacteria inhabit the intenstinal tracts of warm-blooded animals and human beings and appear in very large number in their daily faecal discharges and also in crude sewage. They by themselves are not harmful but their presence serves to indicate the possible existence in water of the pathogenic type of bacteria such as the typhoid bacillus etc., which may be the cause of water pollution. It is, therefore, important for tests to be carried out to indicate the presence or otherwise of E coli before declaring water absolutely fit for human consumption. The source of water to any treatment plant can be either a surface or subsurface source supplying through dug well, shallow and deep well and bored well. The raw water can be

Performance Evaluation of WTP at Gadchiroli protected from any kind of pollution or contamination, activates which adversely affected on human health, economy or good environment.

2.2.5 Surface Water Treatment System The sequence of water treatment units in a water treatment plant mostly remains same, as the principle objectives are to remove turbidity and disinfection to kill pathogens. The first treatment unit in a water treatment plant is aeration, where water is brought in contact with atmospheric air to fresh surface water and also oxidizes some of the compounds, if necessary. Many Water treatment plants do not have aeration system. The next unit is chemical addition or flash mixer where coagulant (mostly alum) is thoroughly mixed with raw water by way of which neutralization of charge of particles (coagulation) occurs. This water is then flocculated i.e bigger floc formation is encouraged which enhances settlement. The flocculated water is then taken to sedimentation tanks or clarifiers for removal of flocs and from there to filters where remaining turbidity is removed. The filtered water is then disinfected, mostly with chlorine and then stored in clear water reservoirs from where it is taken to water distribution system

2.2.6 Aeration This is the process of bringing waters into intimate contact with air with the object of driving out objectionable dissolved gases and oxidizing other soluble compounds present in the ground waters or in stagnant waters of pools and reservoirs. Aeration is effected in many ways- (i) by causing the waters to flow over weirs and waterfalls called Cascade aerators, (ii) by dropping water through perforated plates, (iii) by forcing it through spray nozzles, (iv) by filtering through perforated trays, coke beds, and

(v)

through special devices which aspirate air by diffusion through porous plates. The spray nozzle is the most effective aerator. Aeration is effective in removing 70 to 75 percent of the odours. Removal of carbon dioxide is equally high. Aeration is the one of the important unit operation of gas transfer. The aim of the aeration is to create extensive, new, and self-renewing interfaces between air and water, to keep interfacial films from building up in thickness. The objectives of aeration are as follows 

It removes tastes and odours caused by gases due to organic decomposition.

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It increases the dissolved oxygen content of the water.

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It removes hydrogen sulphide, and hence odour due to this is also removed.

Performance Evaluation of WTP at Gadchiroli 

It decreases the carbon dioxide content of water, and thereby reduces its corrosiveness and raises its pH value.

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Due to agitation states, so that these can be precipitated and removed.

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It is also used for mixing chemicals with water, as in the Aeromix process and in the use of diffused compressed air.

2.2.7 Flash Mixer In a Flash Mixer, the rapid mixing is caused in a rectangular chamber, by the revolutions of a propeller fixed to a propeller shaft and driven by an electric motor. Flash mixer is designed so that the displacement capacity of the impeller is greater than the maximum flow through the chamber so that the alum solution and water are ‘folded’ together in one quick mix. Consequently, alum consumption is held to the necessary optimum for adequate treatment. The detention period is generally to 1 minute, velocity of impeller 3 to 10 revolutions per minute and the velocity of flow at the periphery less than 75 cm per second. In a Flocculator the slow striing is mechanically brought about inside a circular tank equipped with paddles revolving on a vertical shaft. The paddles operate at 2 to 3 revolutions per minute. Time allowed for flocculation varies from 30 to 60 min. In the clarifier, small scrapers are attached to radial arms moving towards s sludge-sum from where sludge can be continuously removed. The mechanically-operated mixing basins have such advantages over the baffle-type basins as (i) reduction in the amount of coagulant (as much as 40 percent) due to more thorough mixing (ii) negligible loss of head, which in the case of baffle-type basins is higher, about 0.6m, (iii) greater flexibility of operation and (iv) lesser cost of installation.

Performance Evaluation of WTP at Gadchiroli

Fig. Flash mixer

2.2.8 Clariflocculator Clariflucculator is widely use in India for the reason that both the flocculators and sedimentation process are effectively incorporated in the single unit. These are provided a central flocculation chamber consisting paddles rotating on their vertical axis with wide outlets ports at the bottom to the clarified zone to maintain the low velocity.

2.2.8.1 Flocculation From the mixing basin water is taken to flocculators for flocculation. Flocculation of slow mixing is the hydrodynamics process which provide adequate opportunity for the microflocs formed during the process or rapid mix to come together to form aggregates of readily settable size. Mechanical flocculator consists of tank provided with paddles for stirring of water, and hence these are also known as flocculator. Depending on the direction of flow water in the tank the mechanical flocculators are classified as. 1) Longitudinal flow flocculator and 2) Vertical flow flocculator

Performance Evaluation of WTP at Gadchiroli

2.2.8.2 Sedimentation Tanks or Clarifiers A sedimentation tank also called setting tank or clarifier, the operation involved is either to detain unflocculated water containing heavier and suspended. Impurities and thereby cause them to settle out or to let the flocculated water flow in from the mixing basin and allow the flocculent precipitate to settle out of suspension. Tanks involving operation of the first kind are called Plain Sedimentation Tanks and those of the second kind as Chemically-aided Sedimentation Tanks. In operating these tanks, two methods have been in use (i) the intermittent or fill and draw method in which the sedimentation takes place during the period the tank stands full, after which the rank is empties. (ii) The continuous method in which water is allowed to flow continuously and slowly through the tank while the sedimentation takes place. The first of these methods i.e., the fill-and–draw method is now obsolete because it requires considerable labour and has no comp0ensating advantages.

Sedimentation tanks are now almost exclusively

operated on the continuous-flow method. The mixing process not only mingles the coagulants with the water but has a very great effect upon the formation of the floc. It is usual to introduce the chemical at some point of high turbulence in the water. After the dose of the chemical is added to the raw water, through mixing is provided by the flash mixer. Rapid mixing is an operation by which the coagulant is uniformly dispersed through the incoming volume of raw water. This help in the formation of micro flocs and result in proper utilization of chemical coagulant preventing localization of concentration and premature formation of hydroxides which lead to less effective utilization of coagulation. The flash mixer is provided with an agitator for thorough mixing of chemicals with raw water. The detention period generally adopted for these tanks is 2 to 2.5 hours with surface overflow rate ranging from 30 to 40 m3/day/m2.

Performance Evaluation of WTP at Gadchiroli

Fig. Clarriflocculator

2.2.9 Filtration Filtration is the most relied water treatment process to remove particulate material from water. Coagulation, flocculation and settling are used to assist the filtration process to function more effectively. The coagulation and settling processes have become so effective that some times filtration may not be necessary. However, where filtration has been avoided, severe losses in water main carrying capacity have occurred as the result of slime formation in the mains. Filtration is still essential. .

2.2.9.1 Classification of filter 1) On the basis of filtration rate a) Slow sand filter

b) Rapid sand filter

Rapid sand filter are also classified as a) Rapid sand

b) Presser filter

Performance Evaluation of WTP at Gadchiroli

Fig. Rapid sand filter

In conventional water treatment, rapid sand filters are commonly adopted. The capacity of the rapid sand filters should be such that the number of unites can take care of the total quantity of water to be filtered. The smaller the number of units, the favor the appurtenances but the larger the wash water equipment that will be required, while designing large size filters one must consider the rate at which wash water dust be supplied and the hydraulic problems for securing uniform distribution of wash water due to the large area. A maximum area of 26 m2 for a single unit can be provided for plants of greater than 130 m3/hr. a) Sand shall be of hard and resistant quartz and free of clay, fine particles, soft grains and dirt of every description. b) Effective size shall be 0.45 to 0.70 mm. c) Uniformity coefficient shall not be more than 1.7 also not less than 1.3. d) Ignition loss should not exceed 0.7 percent by weight. e) Soluble fraction in hydrochloric acid shall not exceed 5% weight. f) Silica content should not be less than 90%. g) Specific gravity shall be in the range between 2.55 to 2.65. h) Wearing loss shall not exceed 3%.

Performance Evaluation of WTP at Gadchiroli

2.2.9.2 Depth of Sand Usually the sand layer has a depth of 0.60 to 0.75 m, but for higher rate filtration when the coarse medium is used deeper sand beds are suggested. The standing depth of water over filter varies between 1 to 2 m. The free board above the water level should be at least 0.5 m so that when air binding problems are encountered, it will facilitate the additional levels of 0.15 m to 0.30 m of water being provided to overcome the trouble.

2.2.9.3 Filter Sand The selected filter sand should be free from clay, loam, vegetable or organic matter. It should also be uniform and of proper size. If the sand is too fine, it tends to quickly clog, causing a greater loss of head in the filter and if it is too coarse, it will permit suspended solids and bacteria to pass through the voids between the sand grains. It is usual, therefore, to classifuy the filter sand by such characteristics as the effective size, the uniformity coefficient and the percent size. Effecftive size of the sand is defined as the sieve size in mm which permits 10 percent of the sand, by weight to pass or in other words, as the size of the grain that is larger than 10 percent by weight of all the particles comprising the sand. This expression would merely indicate the minimum size of 90 percent by weight of the sand. This does not give any information about the degree of variation in the sizes of the particles or about the sizes of the largest and smallest grains. It is found that considerable variation in individual grain size adversely affects the efficiency of the filter. Uniformity Coefficient of sand is an expression of the degree of variation. This may be defined as the ratio between the sieve size that will pass 60 percent by weight to the effective size or in other words, as the ratio of the particle size which isn coarser than 60 percent by weight of the sand to the effective size of sand. Thus, if sand has an effective size of 0.50 mm and 60 percent of sand passes a 0.80 mm. Sieve, the uniformity coefficient =

.

Recently, with certain special sands, it is found that the expression percent size is more suitable than effective size. Percent size may be defined as the size of the grain that has the given percent by weight, of materials finer in size. On this basis, sands, 1, 10, 60 and 90 percent sizes are specifies. Thus a percent size of 10 means that 10 percent of the sand is smaller than the grain size given. The advantage of this method is that the percent size of sand can be directly specified without plotting as is done for the effective size determination. This amounts to a simplified procedure.

Performance Evaluation of WTP at Gadchiroli Percent Size Distribution of Filter Sand Grains.

Percent Size 1 10 60 90

Grain size, mm Fine Min. Max. 0.26 0.32 0.35 0.45 0.53 0.75 0.93 1.50

Medium Min. 0.34 0.45 0.68 1.19

Max. 0.39 0.55 0.91 1.80

Coarse Min. 0.41 0.55 0.83 1.46

Max. 0.45 0.65 1.08 2.00

2.2.9.4 Filter Washing This is carried out by the processes of air scour and backwashing i.e. by sending air and water respectively upwards through the filter bed. As the filter is drained out leaving a few cm. Depth of water standing above the top of the bed, compressed air is sent under pressure through the under-drainage system for about 2-3 minutes. This agitates the mass of water and the dirt from the surface of sand grains is loosened. An upward flow of water from a high level tank is now sent through the bed. This causes the sand-bed to expand, agitate the sand grains and wash off the surface-deposits, which are then collected in troughs placed 15-30 cm above the top of the filter and carried away to the washwater drain. It is important that the velocities of air scour and back flow are properly controlled so that the sand grains are not bodily carried out with the surface wash-water. In the air wash system, the air is forced through the under-drains before the wash water is introduced. Free air of about 36 to 45 m/h (600 to 900 lpm/m2 of the filter area) at 0.35 kg/cm2is forced through the under drain until the sand is thoroughly agitated, for a period of about 5 minutes, following which wash water is introduced through the same under at a rate of 24 to 36 m/h (400 to 600 lpm/m2of area). In the practice backwashing employing conjunctive air and water wash air is usually applied at a rate of 45-50 m/h and water 12-15 m/h.

Performance Evaluation of WTP at Gadchiroli

2.2.10 Disinfection Chlorination became the accepted means of disinfection and it is the single most important discovery in potable water treatment. Recently, however the concern over disinfection byproducts (DBPs) produced by chlorine has given new impetus to investigating alternative disinfectants. Disinfection of potable water is the specialized treatment for destruction or removal of organisms capable of causing disease, it should not be confused with sterilization, which is the destruction or removal of all life. Pathogens (disease producing organisms) are present in both groundwater and surface water supplies. These organisms, under certain conditions, are capable of surviving in water supplies for weeks at temperatures near 21° C, and for months at colder temperatures. Destruction or removal of these organisms is essential in providing a safe potable water supply. While the exact effect of disinfection agents on microorganisms is not clearly understood, some factors that affect the efficiency of disinfection are as follows 

Type and concentration of microorganisms to be destroyed



Type and concentration of disinfectant



Contact time provided



Chemical character and



Temperature of the water being treated

2.2.10.1 Chlorination Chlorination is the application to water of small quantities of chlorine or chlorinecompounds. The dose applied is generally less than 1 mg/l. The dose applies is tity varying from a trace to about 0.05 to 0.20 mg/l. The amount of chlorine so required to be added depends upon the chlorine demand of water, which is the difference between the amount of chlorine added and the amount of chlorine remaining at the end of a contact period of 10-20 minutes. Chlorination possesses great disinfecting powers, as such this method is universally employed for disinfecting public water supplies. Chlorine reacts with water to produce hypochlorous acid (HOCI) and hypochlorite ion (OCI), which are together known as free available chlorine. The chemical action may be represented as Cl2 + H2O --- HOCI + HCI HOCI = H+ + OCI-

Performance Evaluation of WTP at Gadchiroli If ammonia is also present in water, other compounds formed are monochloramine (NH2CI) and dichloramine (NHCI2) which are together known as combined available chlorine. These resulting chlorine-compounds either in the form of free or combined available chlorine interferes with certain enzymes in the bacterial cell-wall forming a toxic chloro-compound thus destroying the bacterial completely. Another theory ascribes the destruction of bacteria to the liberation of nascent oxygen (HOCI=HCI+O) which oxidizes the organisms. This theory is now considered inadequate and obsolete on the grounds that the quantity of nascent oxygen produced is too less for the purpose and further that other equally powerful oxidizing agents like hydrogen peroxide do not possess the same disinfecting power. Chlorine is the chemical predominantly used in the disinfection of potable water supplies. The first application of chlorine in potable water treatment was for taste and odour control in the 1830s. At that time, diseases were thought to be transmitted by odour. This false assumption led to chlorination even before disinfection was understood. Currently, chlorine is used as a primary disinfectant in potable water treatment. Other use include taste and odor control, algae control, filter-media conditioning, iron and manganese removal, hydrogen sulfide removal, and color removal. Through physio-chemical process such as aeration, coagulation, flocculation, sedimentation and filtration assist in removal of microorganisms to varying degree, these can not be relied upon to provide safe water. As indicated in the previous section a consideration amount of bacteria and other micro-organisms present in raw water are removed by filtration, but the water obtained from filter still contain bacteria and other micro-organisms, some of which may be pathogenic. The water obtaining from filter is therefore not safe for drinking purpose, it is necessary to kill the disease producing bacteria and other micro-organism present in it. The need for disinfection in ensuring protection against transmission of water borne diseases cannot be overemphasized and its inclusion as one of the water treatment process is considered necessary. Chlorination is achieved by mean of either liquid or gaseous chlorine of bleaching powder.

2.2.10.2 Forms of chlorination Depending upon the stage of treatment at which chlo0rine is applied to water and also upon the expected result of application of chlorine may be of the following form: i.

Plain chlorination (simple chlorination)

ii.

Pre-chlorination

vi.

iii.

Post-chlorination

vii. Super-chlorination

iv.

Double or multiple chlorination viii.

Break point chlorination

Dechlorination

Performance Evaluation of WTP at Gadchiroli

Performance Evaluation of WTP at Gadchiroli

Table showing unit operations and unit processes of water treatment plant. Sr .No. 1.

Units Micro strainer

UO (or) UP UO

2.

Aeration

UP

3.

Mixing

UO

4.

Pre-oxidation

UP

5.

Coagulation

UP

6.

Flocculation

UO

7.

Sedimentation

UO

8.

Filtration

UO

9.

Disinfection

UP

Note: UO – Unit Operations UP – Unit Process

Principle Applications Remove algae and plankton from the raw water Strips and oxidizes taste and odour causing volatile organics and gases and oxidizes iron and manganese. Aeration systems include gravity aerator, spray aerator, diffuser and mechanical aerator. Provides uniform and rapid distribution of chemicals and gases into the water. Application of oxidizing agents such us ozone, potassium permanganate, and chlorine compounds in raw water and in other treatment units; retards microbiological growth and oxidizes taste, odor and colour causing compounds Coagulation is the addition and rapid mixing of coagulant resulting in destabilization of the colloidal particle and formation of pin-head floc Flocculation is aggregation of destabilized turbidity and colour causing particles to form a rapid-settling floc Gravity separation of suspended solids or floc produced in treatment processes. It is used after coagulation and flocculation and chemical precipitation. Removal of particulate matter by percolation through granular media. Filtration media may be single (sand, anthracite, etc.), mixed, or multilayered. Destroys disease-causing organisms in water supply. Disinfection is achieved by ultraviolet radiation and by oxidative chemicals such as chlorine, bromine, iodine, potassium permanganate, and ozone, chlorine being the most commonly used chemical

Performance Evaluation of WTP at Gadchiroli

METHODOLOGY & MATERIALS Methodology Evaluation procedure followed in water treatment plant for achieving the objectives of the study work were detail study of the plant performance including operation problems. Testing and plant safety. The analysis was carried out in accordance with the following steps, Collection of basic data, plant observation, performance evaluation, and appraisal of laboratory as summarized in tables.

Table 3.1: Summary of Evaluation Procedure Collection Of

Treatment flow sheet and plant design data, plant layout, engineering details

Basic including design, drawing and operating reports for individual treatment unit.

Data

Characteristics of plant influent and effluent, Laboratory facilities, plant persons (i.e. no. of staff, their qualification and experience), and other relevant details such as power consumption etc.

Plant

Pumping and flow measurement, water quality, pre-treatment, chemical dosing,

observations chemical mixing and flocculation, sedimentation ( clarity of settled water), filtration (Influent and effluent turbidity, back washing operation, filter appearances and problems) Performance Flow measurement, sampling and analysis, assessment of individual treatment Evaluation

units with engineering and water quality parameters as appropriate. Identification of deficiencies, in operation and maintenance, if any.

Laboratory

Sampling records, instrument and Equipment used, and review of analysis

evolution

results.

Performance Evaluation of WTP at Gadchiroli

3.2 Activities, Operations & Design of Water Treatment Unit 3.2.1 Raw water Sump and Pump House Pure water sump is provided for storing the filter water & pumps it for distribution to meet the demand of portable water. The filtered water, after the chlorination for disinfection flows to the pure water sump through the conveying main. The pure water sump is provided with an overflow arrangement. The sump and pump house has constructed near to the Bormada Ghat of Wainganga river basin. The water is first collected by intake structure and sump is R.C.C. tank the size of is 18 m x 8 m x 3.50 m and the capacity of sump 520 m3. Here a pump 2 HP, two pumps of 1 HP & 20 mud pumps are in used.

3.2.2Aeration The raw water discharges at the center of the concentric aeration fountain through the central inlet shaft & flows down the step to the peripheral launder. Weirs and waterfalls of any kind are cascade aerator. Cascade is of a series of four step of concrete. Water is allowed to fall through height of 1 to 3 meter, and due to this it comes into close contact with air. The reduction of CO2 is usually in the range of 50 to 60%. The diameter of bottom cascade fountain is 5.1 m and top cascade is 1.2 m. R.L of cascade in 104.50 m and bottom cascade is 103.45 m. 6.3 m width of collecting chamber is provided with height 0.60 m. The aerated water is collected in open channel of 1200 mm wide Parshall flume for measurement of flow and then transferred to flash mixer.

Performance Evaluation of WTP at Gadchiroli Table 3.2 Design criteria for cascade aerator

Objective

To extensive, new, and self-renewing interfaces between air and water, to keep interfacial films from building up in thickness.

Design Parameter

Design capacity

Rate of flow 30 MLD

Assuming G.L.

100.00 m

No. of Cascades

4 Nos.

Lip of Aerator fountain

104.050 m

Top level of 1st cascade

103.900 m

Top level of 2st cascade

103.750 m

Top level of 3st cascade

103.600 m

Top level of 4st cascade

103.450 m

Outer Diameter pf Vertical Shaft

0.60 m

Inner Diameter pf Vertical Shaft

0.560 m

Total Diameter 1st cascades

1.50 m

Total Diameter 2st cascades

2.70 m

Total Diameter 3st cascades

3.900 m

Total Diameter 4st cascades

5.10 m

Size of water channel

1.5 m(wide) x 1.2 m (depth) (0.80 m water depth + 10 cm free board)

Top level of water channel

104.050 m

Bottom level of water channel

103.450 m

Bottom level of vertical shaft

103.150 m

Velocity

0.60 m/sec

Expected

It should increase in Dissolved Oxygen and remove other gases from water.

Output

& completely removing of taste and odours cascade by gases.

Performance Evaluation of WTP at Gadchiroli

Fig. 3.2 Aerator 3.2.3 Raw water flow measurement This unit is provided to monitor the raw water entering into the treatment plant. A flow meter is installed for measuring the raw water flow. A Parshall flume of 1200 mm wide has been provided in the raw water inlet chamber. The flow measuring device with a capacity of 30 MLD to measure flow. The type flow measuring element is rectangular notch type. The measuring device is of float operated flow type indicator gauge pedestral type with flat chamber which is not in working condition. The variation of water level in the flot chamber is transmited to he pointer by the movement of the float & the pointer indicates the raw water flow.The width of throat of this is 1000 mm.

3.2.4 Coagulant dosing chemical house This unit is provided of an instantaneous & through out mixing of chemicals that are added to the raw water. There are four no. of tanks, two for alum solution & two for lime bleaching powder solutions. The effective capacity of tank are 2600 liter.The alum dose to be administrated is 26.00 kg/hr. The capacity of storage of alum is for 4 months and the size of chemical house is 10.0 m x 3.50 m. There is a unit having size Diameter 2.30 m & 3.00 m (depth). The design rate of flow is 30 MLD. Presently they are using alum bricks in liquid from at raw water channel through a perforated plastic pipe located about 50 cm above the water surface, some of perforation was found clogged.

Performance Evaluation of WTP at Gadchiroli

3.2.5 Flash Mixer The measured quantity of raw water along with chemical dosed enters into side jacket and is admitted in the flash mixer through the bottom opening in the well. The flash mixer is 2.30 m diameter and 3.0 m deep with four baffle walls for better mixing of 12.5 MLD capacities. The motor of 1 HP has been provided with 500 rpm. The flash mixer is well equiped with a suitable speed agiator forensuring the proper mixing of chemicals with raw water. By pass arrangement is also provided for the raw water to the filter beds, when the chlorriflocculator is under maintenance. One no. of M. S. shutter is provided for bypass utility.

Table 3.3 Design criteria of flash mixer

Objective

To disperse the chemical coagulant effectively in the raw water thereby causing complete destabilized of colloidal impurities and formation of micro floc.

Design

Designed capacity

12.5 MLD

parameter

Diameter of mixer

2.30 m

Water Depth

3.00 m

F.S.L.

103.450 m

Bottom level

102.720 m

Detention period

1 min

Value of G to be achieved

300/sec

Free board

0.40 m

Motor H.P.

1 H.P (Kirloskar make gear)

Velocity Gradient

300/sec

Expected

Complete destabilization of colloidal impurities and formed micro flocs

output

which can be readily agglomerated in the sequence process of slow mixing

Performance Evaluation of WTP at Gadchiroli

3.2.6 Clariflocculator Along with the object of clariflocculator to form distinct setteable flocs during flocculation & their removal by gravitational setting in the clarifying zone. The clear water overflows leaving behind the settleable solids, the coagulated water enters at about of flocculator. The flocculator has a diameter of 9.72 m while the clarifier has a diameter of 23.90 m and depth 3.55 m. Along the periphery of tank the channel has been provided with V-notch. The settled flocs are colected in the central circular channel around the inlet column by a set of scraper arms fixed to a rotating M.S. Bridge is 48 rounds per hour. The central sludge channel is provided with a local depression to accommodate a chamber from where the collected sludge is withdrawn periodically for disposal through the manhole. The clear water leaving behind the setteable solids overflows into the peripheral launder & is led to the subsequent unit for further treatment. Table 3.4 Design criteria of Flocculator

Objective

To Produce readily settable floc destabilized colloidal particles.

Design

No. of units

parameters

Design

flow

1 (Radial flow clarifier with conc. flocculator) through 520.00 m2/hr

clariflocculator unit Detention period

30 min(10-30 minutes )

Diameter

9.72 m

Velocity Gradient

30 sec-1(10-75 sec-1)

Surface overflow rate

21.88 m3/m2/day

Weir loading

17.46 m3/m/day

Expected

The flocs formed during flocculation settles readily in the sedimentation basin

Output

and filter box. The floc strength should be sufficient to withstand shearing that may be encountered during its travel to the sedimentation basin.

Table 3.5 Design criteria of Clarifier. Objective

To Objective of the sedimentation is to permit effective sedimentation and flocculation process. No. of units

1 (Peripheral type)

Capacity of each unit Design flow 520.00 m2/hr

Performance Evaluation of WTP at Gadchiroli through clariflocculator unit Detention period

150 min.

Diameter

23.90 m

RPM of blades

10 RPM

Design

Floor slope

1:12

Parameters

Weir loading

17.46 m3/day/m2

Surface loading

21.88 m3/m2/day

Turbidity

< 10 NTU

Velocity of water in collecting