Environmental Engineering II

Transcription

1 Environmental Engineering II Prof. Rajesh Bhagat Civil Engineering Department Y.C.C.E.,Nagpur B. E. (Civil Engg.) M. Tech. (Enviro. Engg.) GCOE, Amravati VNIT, Nagpur Experience & Achievement: Selected Scientist, NEERI-CSIR, Govt. of India. GATE Qualified Three Times. Selected Junior Engineer, ZP Washim. Three Times Selected as UGC Approved Assistant Professor. Assistant Professor, P.C.E., Nagpur. Assistant Professor, Cummins College of Engg. For Women (MKSSS, Nagpur) Mobile No.: / Website:- ID :- rajeysh7bhagat@gmail.com

2 UNIT-V 1) Rural sanitation: Pit Privy, Aqua Privy, Bio-gas Recovery, Eco-Sanitation. Septic tank including soak pit, Imhoff tanks. 2) Industrial Waste Water Treatment: Basic concepts of Industrial Waste Water Treatment, flow equalization, neutralization. Common treatment alternatives for industrial waste water. 2

3 Rural Sanitation:- In India, more than 70% of population of our country resides in villages and small towns. The term rural sanitation is used to indicate the development or maintenance sanitary condition in rural areas. Necessity of Rural Sanitation:- 1) There is no proper waste disposal facilities in rural area with the result that many a people fall victim to various diseases like typhoid, dysentery, etc. 2) It is therefore necessary to provide better facilities like construction bore-hole privy, latrines and surface drainage, etc. 3) Also there should be arrangement for drainage of storm water. 4) Tapped water is the most essential requirement. 5) Well should be properly protected from nearby drains, etc.

4 In India, more than 70% of population of our country resides in villages and small towns. The term rural sanitation is used to indicate the development or maintenance sanitary condition in rural areas. Rural Sanitation:- Privies:- In conservancy system the human excreta is collected by various types of container or structure known as privy. Types:- 1) Trench privy 2) Pit privy or Dug well privy 3) Bore hole privy 4) Can privy 5) Concrete vault privy 6) Chemical toilet 7) Aqua privy 8) Pour flush water seal latrine

5 Trench Privy:- 1) Used as temporary measure during fairs, camps, etc. 2) Consists of rows of parallel trenches 0.9m long, 0.3m & 0.4m deep. 3) The faeces, urine ablution water fall directly into the trench. 5

6 Pit Privy:- 1) Consists of pit 0.9m to 1.2m in diameter & 2 to 4 m deep. 2) Pit may be lined or unlined but its bottom is unlined. 3) Pit is covered with squatting plate. 4) When pit gets filled, the squatting plate or superstructure is shifted to another pit and the old one is covered with earth. 5) Soil bacteria renders excreta harmless after a couple of months, when the contents can be turned over and used as a manure. 6) Its use is restricted due to place and space. 7) Water table should be low to avoid pollution of GW. 8) Odor problem can be controlled by use of lime. 9) This is very economical and require no operations. 6

7 Bore Hole Privy:- 1) Constructed where space available is less. 2) Similar to pit privy except depth is more. 3) Consists of hole of 0.3m to 0.4m diameter & 5 to 6m deep. 7

8 Can Privy:- 1) Also known as removable receptable privy. 2) Oldest method & still used in rural area. 3) Can is placed under the seat or squatting plate for the collection of the faeces, urine & ablution water. 4) Initial cost is low but servicing cost is high. 8

9 Concrete Vault Privy:- 1) Improved form of pit or bore hole privy. 2) Used in sandy soils or in locations where ground water-table is high. 3) Watertight concrete vault or chamber constructed underground for collection & storage of faecal matter. 4) Squatting seat is provided over the top of vault. 5) No water is used. 6) When it is filled, then emptied through the manhole. 9

10 Chemical Toilet: 1) Concrete vault is replaced by an acid proof metal tank. 2) Tank is of capacity 600 liters. 3) The caustic soda helps to stabilize the organic matter present in the excreta. 4) Cost is more hence not used in rural areas. 5) Used in aircraft.

11 Aqua privy 1) It is based on the principle of septic tank action where by the tendency of excreta to liquefy anaerobically when enclosed in a water tight tank. 2) It consist of square plate with a drop pipe 10cm diameter extending 10 to 15cm into a water tight tank to point below the water tank. 3) Faeces and urine fall into the tank where they undergo decomposition as in the septic tank. 4) The solid are reduced in volume to about a quarter of the faeces deposited. 5) The effluent is led of from the tank to undergo further treatment either in the seepage pit or subsoil absorption field. 6) Solids remaining in the tank have to be removed periodically.

12 Pour Flush Water Seal Latrine: 1) The excreta is hand flushed by pouring about 1.5 to 2 litres of water. 2) Consists of leaching pits located slightly away from the pan. 3) Usually two leaching pits are provided but at a time squatting pan is connected to only one pit.

13 Septic Tank :- 1) In rural area or in case of isolated building underground sewerage system with complete treatment of sewage neither be feasible nor be economical. 2) Under such cases, septic tanks are preferred by subsurface disposal off effluent are provided in area having porous soil. 3) Location of septic tank should be away from the building. 4) Septic tanks are horizontal continuous flow, small sedimentation tanks through which sewage is allowed to flow slowly to enable the sewage solids to settle to the bottom of the tank, where they are digested anaerobically. 5) Biochemical reactions by anaerobic bacteria takes place. 6) The tank is de-sludged at regular intervals usually once every 1-5 years. 7) Effluent is taken to soak pits for disposal. 8) The bas smell occur during the digestion period of sludge & hence septic tank are provided with cover at the top. 13

14 Septic Tank :- 14

15 Disposal of Septic Tank Effluent:- Effluent is malodorous containing pathogenic organism hence needs to be disposed of carefully. Disposed of by land disposal methods or soil absorption methods. Effluents is allowed to be soaked or absorbed by surrounding soil. 1. Soak Pits or Seepage Pits 2. Dispersion Trenches 15

16 Soak Pit or Seepage Pit:- 1) A circular covered pit, through which effluent is allowed to be soaked into surrounding soil. 2) Soak pit may either be filled with some stones or aggregates or may kept empty. 3) Effluent of cesspool, aqua privy, septic tank or sullage from bathrooms & kitchens. 4) Difference between soak pit & cesspool is that the soak pit is completely filled up with stones. 5) The fine suspended solids adhere to the surface of stones and get decomposed by the film, which are on the stones and the effluent is leached into the side walls. 16

17 Dispersion Trenches:- Narrow & shallow trenches about 0.5 to 1 m deep & 0.3 to 1 m wide excavated to a slight gradient of about 0.25%. Open jointed earthware or concrete pipes of 80 to 100 mm diameter are laid in the trenches over a bed of 15 to 25 cm of gravel. 17

18 Bio-Gas Production: 1) Plays a significant role in sanitation.. 2) Powerful source of energy & fertilizer supply in rural areas. 3) Anaerobic fermentation of organic substances such as cattle dung (gobar), green leaves, animal urine, animal fodder, night soil, kitchen waste, etc. 4) Biogas is mixture of 2/3 rd of methane (combustible) & 1/3 rd is carbon dioxide with traces of nitrogen, hydrogen sulphide, hydrogen, oxygen, & ammonia.

19 Uses of Bio-Gas Production: 1) Used for cooking, lighting, driving oil & gas engine. 2) Makes an efficient use of the slurry produced after digestion in the bio-gas. (Compost) NPK 3) Eliminate nuisance due to mosquitoes, flies & insect breeding on exposed cattle dung. 4) Prevent of eye diseases caused by burning cattle dung cakes in chullahs. 5) Eliminates pollution of atmosphere due to smoke from chullahs.

20 Imhoff Tank:- 1) Improvement over the plain septic tank. 2) Both sedimentation and sludge digestion takes place in the same structured. 3) Contains two compartment one for sedimentation and another for sludge digestion. 4) Upper chamber is known as sedimentation chamber & lower chamber is digestion chamber. 5) Quite economical & not require any skilled attention during operation. 6) Combined advantages of septic tank & sedimentation tank. 7) No moving parts. 8) It is possible to dry easily the sludge. 9) Process is better than septic tank. 10) No adequate control over operation. 11) May give out offensive odor. 12) Depth is more than septic tank. 13) Have tendency to foam or boil (scum at top) 14) Unsuitbale for highly acidic sewage. 20

21 Design a septic tank for a small colony of 200 person provided with a water supply of 200 litres per person per day. Assume suitable date required. Assuming 80% of water supplied appears as sewage. Total quantity of sewage produced = 200 x 200 x 0.8 = litres / day = 32 m 3 /day Assume detention time = 24 hours Capacity of tank required to store sewage = 32 ( 24/24) = 32 m 3 Assume rate of deposited sludge = 30 litres per capita per year Peroid of cleaning one year Capacity for sludge storage = 30 x 200 x 1 = 6000 litres = 6 m 3 Total capacity of tank = = 38 m 3 Assume liquid depth = 1.2m Surface area of tank = 38 / 1.2 = m 2 Take L/B = 2.5 L x B = L x B = B = 3.6m & L = 9m Assume FB = 0.3m Total depth of tank = = 1.5m Hence provide 9 X 3.6 x 1.5 m 21

22 Design a septic tank for hostel with the following data: No. of users = 150 Peak discharge = 205 lpm Desludging period = 1 year 22

23 INDUSTRIAL WASTEWATER TREATMENT:- Characteristics of industrial sewage differ considerably from domestic sewage. Characteristics of industrial sewage vary with the type of industry and even in the same type of industry they vary according to the process involved. Industrial sewage contains chemical pollutants & toxic substances in large proportions. Industrial sewage needs proper treatment before disposal. Various industries are classified based on characteristics of sewage. 1) Food & food processing industries like sugar, canning, dairy, fermentation, etc. 2) Chemical processing industries like chemical manufacturing, paper & pulp, tannery, textile, rubber, electroplating, etc. 3) Mineral Product industries like iron, steel, oil, petroleum, coal, coke, gas, etc. 4) Other industries like atomic power plants, etc.

24 PROCESSES INVOLVED IN INDUSTRIAL WASTEWATER TREATMENT:- Following processes are used: 1) Equalization 2) Neutralization 3) Physical Treatment 4) Chemical Treatment 5) Biological Treatment Factors affecting selection of processes: Flow, Concentration of pollutants, Presence of non biodegradable organics, toxicity, etc

25 General Characteristics of Industrial Wastewater:-

26 INDUSTRIAL WASTEWATER TREATMENT:- EQUALIZATION: For sewage treatment plant of small community, where wastewater flow rate considerably vary with time, and for industrial wastewater treatment plants, where wastewater flow and characteristic varies with time, equalization becomes essential to obtain proper performance of the treatment plant by avoiding shock loading (hydraulic and organic) to the systems. To facilitate maintenance of uniform flow rate in the treatment units, flow equalization is used. This helps in overcoming the operational problems caused by flow variation and improves performance of the treatment plant. Flow equalization is provided for dampening of flow rate variations so that a constant or nearly constant flow rate is achieved. The equalization can also be provided for dampening the fluctuation in pollutant concentration in the incoming wastewater to avoid shock loading on the treatment system; to provide continuous feeding to the treatment system when the wastewater generation is intermittent; to control ph fluctuations or to control toxic concentration in the feed to the biological reactor; and this can also be used to control the discharge of industrial effluent in to the sanitary sewers.

27 Equalization can be of two types: a) Inline: Where all flow passes through equalization basin b) Off-line: In this, the flow above average daily flow is diverted to equalization basin. The pumping is minimized in this case but amount of pollutant concentration damping is considerably reduced. Neutralization Fig. 5.8 Neutralization Tank (18)

28 Activated carbon adsorption Many industrial wastes contain refractory organics, which are difficult or impossible to remove through conventional biological treatment. These materials can be removed by adsorption on activated carbon or synthetic active-solid surface. The degree to which adsorption will occur and the resulting equilibrium relationships have been correlated according to the empirical relationship of Freundlich or the theoretically derived Langmuir relationship. Ion exchange Ion exchange can be used for the removal of undesirable anions and cations from a wastewater. Cations are exchanged for hydrogen or sodium and anions for hydroxyl ions. Ion exchange resins consist of an organic or inorganic network structure with attached functional groups. Most ion exchange resins used in wastewater treatment are synthetic resins made by the polymerisation of organic compounds into a porous three-dimensional structure.

29 Membrane processes The membrane processes can be classified according to the size range of the separated species: 1) Reverse osmosis is used to separate dissolved salts and small organics (size under 1 nm). Example: production of drinking water from seawater or seawater desalination. 2) Nanofiltration is used to separate antibiotics (size under 10 nm). Example: selective demineralisation of water or concentration of organic solutions. 3) Ultrafiltration is used to separate emulsions, colloids,macromolecules or proteins (size under 100 nm).example: treatment of pulp and paper industry s effluents.

30 1) Describe in brief the importance of rural sanitation? 2) What are the requirements to be satisfied by the proper excreta disposal methods? 3) What are different types of privies used in rural sanitation? Explain? 4) Draw a neat sketch and explain the working of Aqua Privy? 5) Draw a neat sketch and explain the working of Pit Privy? 6) Draw a neat sketch of septic tank and explain its working? 7) Explain the disposal methods of septic tank effluent? 8) Design a septic tank for 200 users. Assume the cleaning period of one year. 9) What is the difference between sewage and industrial waste? 10) What are the measures to minimize the concentration of industrial waste? 11) Explain the characteristics of industrial wastewater? 12) What is the significance of Industrial wastewater treatment? 13) Discuss in brief equalization, neutralization, proportioning & floatation? 14) Explain the various chemical processes involved in treatment of industrial wastewater? 15) Write a short notes on:- a) Effluent standards for IWW b) Disposal of IWW c) Pit Privy d) Aqua privy e) Septic tank f) Imhoff Tank g) Soak pit h) Gobar Gas Plant