Unit - 4
Secondary Treatment: Aerobic Suspended and Attach Growth
Q1) What is Secondary Treatment?
A1)
Secondary remedy is the elimination of biodegradable natural be counted (in answer or suspension) from sewage or comparable styles of wastewater. The goal is to obtain a positive diploma of effluent best in a sewage remedy plant appropriate for the meant disposal or reuse option.
A "number one remedy" step frequently precedes secondary remedy, wherein bodily segment separation is used to take away settleable solids. During secondary remedy, organic tactics are used to take away dissolved and suspended natural be counted measured as biochemical oxygen demand (BOD). These tactics are executed with the aid of using microorganisms in a controlled cardio or anaerobic method relying at the remedy technology.
Bacteria and protozoa devour biodegradable soluble natural contaminants (e.g. Sugars, fats, and natural short-chain carbon molecules from human waste, meals waste, soaps and detergent) at the same time as reproducing to shape cells of organic solids. Secondary remedy is broadly utilized in sewage remedy and is likewise relevant to many agricultural and commercial wastewaters. Secondary remedy structures are labeled as fixed-movie or suspended-boom structures, and as cardio as opposed to anaerobic.
Fixed-movie or connected boom structures consist of trickling filters, built wetlands, bio-towers, and rotating organic contactors, in which the biomass grows on media and the sewage passes over its surface. The fixed-movie precept has similarly advanced into transferring mattress biofilm reactors (MBBR) and Integrated Fixed-Film Activated Sludge (IFAS) tactics.
Suspended-boom structures consist of activated sludge, that is an cardio remedy machine, primarily based totally at the renovation and recirculation of a complicated biomass composed of micro-organisms (micro organism and protozoa) capable of take in and adsorb the natural be counted carried withinside the wastewater. Constructed wetlands also are being used.
An instance for an anaerobic secondary remedy machine is the upflow anaerobic sludge blanket reactor. Fixed-movie structures are greater capable of address drastic modifications in the quantity of organic fabric and might offer better elimination prices for natural fabric and suspended solids than suspended boom structures. Most of the cardio secondary remedy structures consist of a secondary clarifier to settle out and separate organic floc or fabric grown withinside the secondary remedy bioreactor.
Q2) Explain Aerobic Suspended Growth
A2)
Aerobic suspended boom remedy procedures encompass activated sludge procedures, sequencing batch reactors (SBR), and aerated lagoons. Owing to the traits of the wastewater, the touch time among the natural wastes and the microorganisms have to be better than that for home wastewater.
Processes with better hydraulic retention time (HRT) and solids retention time (SRT), together with prolonged aeration and aerated lagoon, are advocated to be used. O'Shaughnessy et al. Mentioned that cardio lagoons with extent of 267,800 gallons every had been used to deal with a wastewater from a Coca Cola bottling company. Detention time turned into 30 days; the layout glide turned into 20,000 gpd.
A collection of operational troubles befell withinside the early phase, inclusive of a caustic spill incident, non-stop clogging of air diffusers, and terrible effluent first-class because of surprise loading (e.g., liquid sugar spill). Failure to satisfy effluent requirements turned into a severe hassle withinside the remedy plant. It turned into determined that the effluent BOD5 and COD had been above one hundred and 500 mg/L, respectively.
This hassle, however, turned into solved via way of means of addition of potassium; the effluent BOD5 reduced to 60 mg/L. Tebai and Hadjivassilis used a cardio technique to deal with smooth drink wastewater with a everyday glide of 560 m3/day, BOD5 of 564 mg/L, and TSS of 580 mg/L. Before starting organic remedy, the wastewater turned into first dealt with via way of means of bodily and chemical remedy procedures. The bodily remedy covered screening and influent equalization; withinside the chemical remedy, pH adjustment turned into finished accompanied via way of means of the conventional coagulation/flocculation technique.
A BOD5 and COD elimination of 43.2 and 52.4%, respectively, turned into executed withinside the bodily and chemical remedy procedures. In the organic remedy, the BOD5 loading fee and the sludge loading fee had been 1.sixty four kg BOD5/day m3 and 0.forty two kg BOD5/kg MLSS day; the BOD5 and COD elimination efficiencies had been sixty four and 70%, respectively. The organic remedy turned into operated at a high-fee mode, which turned into the principle purpose for the decrease elimination efficiencies of BOD5 and COD.
Q3) Write a short note on Attach Growth
A3)
Wastewater remedy methods wherein the microorganisms and micro organism treating the wastes are connected to the media withinside the reactor. The wastes being dealt with float over the media.
Trickling filters and rotating organic contactors are connected boom reactors. These reactors may be used for BOD removal, nitrification, and denitrification. Wastewater remedy methods wherein the microorganisms and micro organism treating the wastes are suspended withinside the wastewater being dealt with. The wastes float round and via the suspended growths.
The numerous modes of the activated sludge technique employ suspended boom reactors. These reactors may be used for BOD (biochemical oxygen demand) removal, nitrification, and denitrification. Most micro-organisms can colonise the floor of a substrate while they may be on the boom stage. Bacteria connect themselves to the substrate by using the exopolymers they produce. The preliminary colonisation of a stable takes location on some of preferential webweb sites and it's miles from those webweb sites that the biofilm develops till the full floor region of the substrate is coated.,
At the equal time, new cells are produced and motive the movie to thicken. The oxygen and vitamins carried withinside the water to be dealt with diffuse via the movie till it achieves a thickness such that oxygen now not reaches the inner most mobileular layers. Thus, stratification happens in thick movies with the superimposition of an cardio layer inside which the oxygen diffuses and a deeper anaerobic layer that consists of no oxygen.
Q4) What is suspended growth system?
A4)
The activated sludge procedure is a cardio suspended-boom procedure that keeps a pretty excessive populace of microorganisms (biomass) through recycling settled biomass again to the remedy procedure. The biomass converts soluble and colloidal biodegradable natural count number and a few inorganic compounds into mobileular mass and metabolic quit products.
The biomass is separated from the wastewater through settling in a clarifier for recycling or losing to sludge dealing with processes. Preliminary remedy to do away with settleable solids and floatable substances is typically furnished through a septic tank or different number one remedy device.
Most onsite designs are able to imparting substantial ammonia oxidation and powerful elimination of natural count number. The primary machine includes some of interrelated components - An aeration tank or basin. - An oxygen supply and system to disperse atmospheric or pressurized air or oxygen into the aeration tank at a price enough to constantly preserve high-quality dissolved oxygen. - A manner to as it should be blend the aeration basin and make certain suspension of the biomass (typically achieved through the aeration machine). - A clarifier to split the biomass from the handled effluent and acquire settled biomass for recycling to the aeration basin.
Fig: Suspended growth system
These structures are commonly preceded with the aid of using a septic tank and accompanied with the aid of using a subsurface wastewater infiltration device (SWIS). Despite a few claims of decreased SWIS sizing while as compared to the traditional septic tank pretreatment, the clothier is counseled to don't forget floor water protection.
These structures have to be implemented simplest wherein onsite device control offerings are available. For floor water discharge, the device should be accompanied with the aid of using disinfection at a minimal to constantly meet discharge standards.
However, a few subsurface (non-human-contact) reuse can be applied without similarly treatment. High biomass structures may be a low-fee approach of upgrading present overloaded CFSGAS devices that presently do now no longer meet BOD or nitrification goals. They also can compete immediately with traditional designs due to the fact they've extra balance in coping with particularly variable loadings.
Q5) What is oxidation pond?
A5)
Oxidation ponds, additionally referred to as lagoons or stabilization ponds, are big, shallow ponds designed to deal with wastewater via the interplay of sunlight, micro organism, and algae.
Algae develop the use of electricity from the solar and carbon dioxide and inorganic compounds launched via way of means of micro organism in water. During the manner of photosynthesis, the algae launch oxygen wished via way of means of cardio micro organism.
Mechanical aerators are once in a while mounted to deliver but greater oxygen, thereby lowering the desired length of the pond. Sludge deposits withinside the pond ought to finally be eliminated via way of means of dredging. Algae ultimate withinside the pond effluent may be eliminated via way of means of filtration or via way of means of a mixture of chemical remedy and settling. In this remedy gadget a sequence of big plastic disks established on a horizontal shaft are partly submerged in number one effluent.
As the shaft rotates, the disks are uncovered alternately to air and wastewater, permitting a layer of micro organism to develop at the disks and to metabolize the organics withinside the wastewater.
For the elimination of extra suspended solids and BOD from secondary effluent, effluent sprucing is an powerful remedy. It is most customarily completed the use of granular media filters, just like the filters used to purify ingesting water. Polishing filters are generally constructed as prefabricated units, with tanks located at once above the filters for storing backwash water. Effluent sprucing of wastewater will also be performed the use of microstrainers of the kind utilized in treating municipal water supplies.
Q6) Explain Bacteria – algae symbiosis
A6)
Symbiosis of micro organism-animals: Bacteria are recognized to be very not unusualplace endo and ectosymbiotic microorganisms of humans, bugs and different animals.
All humans accumulate unique micro organism on the beginning as ordinary flowers which stay related during the existence span. Animals which includes farm animals additionally undergo unique micro organism as resident microflora. Normal flowers micro organism connect and colonize epithelial mucus lining of organs of gastrointestinal, genitourinary and respiration tract of animals and humans.
They constitute mutualism in addition to commensalism with the host. Normal flowers gets defensive environment, vitamins and delivery from host even as as host receives deliver of positive B vitamins, improvement and activation of immune gadget and safety from pathogenic microbes. Lactobacilli living in vagina produce lactic acid which protects girl genitourinary tract from infectious yeasts like Candida and different pathogenic microbes.
Rumen micro organism which includes Propionibacterium spp. Living in farm animals gut are cellulolytic and in fact digest cellulosic meals ingested with the aid of using animal; farm animals do not produce other approach of cellulose usage and cellulosic content material of vegetable count could in any other case not possible to degrade without useful resource with the aid of using rumen micro organism. Cooperative interplay among aphids and micro organism Buchnera aphidicola is one of the fine instance of insect and bacterial symbiosis.
Bacteria offer all enzymes vital for the synthesis of vital amino acids which might be missing in aphid meals (plant sap); in go back aphids synthesize enzymes required to accumulate bacterial mobileular wall. Another instance of micro organism-animal symbiosis is of gutless worms of deep hydrothermal vents.
They have sulfur oxidizing micro organism as endosymbionts; due to the fact that they do not have digestive tract, they may be absolutely depending on vitamins supplied with the aid of using those micro organism.
Association of squids, jelly fish and fishes like angler fish and lantern fish with luminescent micro organism is thrilling instance of symbiotic interplay. Bioluminescence is obtained with the aid of using luminescent micro organism like Vibrio fischeri which harbor within the mild organs of those animals; it's miles very beneficial for area of prey, as course finder in deep sea regions, to draw mate or to warn off or repel the predators.
Q7) Give advantages & disadvantages of oxidation ponds
A7)
Advantages:
The stabilization pond reduces the organic oxygen call for as much as 90% naturally.
It is a easy technique to perform or does now no longer require state-of-the-art equipment.
Oxidation pond is a realistic and powerful technique for the wastewater remedy of home and change wastes in tropical areas.
The operation of a stabilization pond does now no longer require a great deal labour-power.
It is a cost-effective technique for the remedy of wastewater from small and remoted units.
The oxidation pond remedy system is natural, as it makes use of microorganisms including micro organism and algae.
This makes the approach of remedy cost-powerful in phrases of its construction, maintenance, and strength requirements.
Oxidation ponds also are productive, as it generates effluent that may be used for different applications. Finally, oxidation ponds may be taken into consideration a sustainable approach for remedy of wastewater.
Disadvantages:
The creation of a stabilization pond calls for greater land area.
The upkeep is pretty intricate. Sometimes, it offers a bad odor and mosquito threat in the course of the technique if now no longer correctly maintained.
There may also get a danger of effluent seepage into the floor water, that can in the end purpose floor water pollution.
Q8) What are aerated lagoons?
A8)
An aerated lagoon (or aerated pond) is a easy wastewater remedy gadget including a pond with synthetic aeration to sell the organic oxidation of wastewaters.
There are many different cardio organic approaches for remedy of wastewaters, as an instance activated sludge, trickling filters, rotating organic contactors and biofilters.
They all have in not unusualplace the usage of oxygen (or air) and microbial movement to lessen the pollution in wastewaters. Suspension combined lagoons, wherein there's much less electricity supplied through the aeration gadget to maintain the sludge in suspension.
Facultative lagoons, wherein there's inadequate electricity supplied through the aeration gadget to maintain the sludge in suspension and solids settle to the lagoon ground. The biodegradable solids withinside the settled sludge then degrade as in an anaerobic lagoon.
Suspension combined lagoons go with the drift via activated sludge structures wherein the effluent has the identical composition because the combined liquor withinside the lagoon.
Typically the sludge may have a house time or sludge age of one to five days. This way that the chemical oxygen demand (COD) eliminated is enormously little and the effluent is consequently unacceptable for discharge into receiving waters.
The goal of the lagoon is consequently to behave as a biologically assisted flocculator which converts the soluble biodegradable organics withinside the influent to a biomass that is capable of settle as a sludge. Usually the effluent is then installed a 2nd pond wherein the sludge can settle.
The effluent can then be eliminated from the pinnacle with a low COD, whilst the sludge accumulates at the ground and undergoes anaerobic stabilisation.
Q9) What is the principle of aerated lagoon?
A9)
Lagoons are pond-like our bodies of water or basins designed to receive, preserve, and deal with wastewater for a predetermined length of time. If necessary, they're coated with material, inclusive of clay or a synthetic liner, to save you leaks to the groundwater below.
In the lagoon, wastewater is dealt with via a aggregate of physical, biological, and chemical processes. Much of the remedy takes place naturally, however a few structures use aeration gadgets to feature oxygen to the wastewater. Aeration makes remedy greater efficient, in order that much less land place is necessary. Aerators may be used to permit present structures to deal with greater wastewater.
Lagoons need to be in my view designed to in shape a particular use. Designs are primarily based totally on such elements as kind of soil, quantity of land place available, and climate. A critical layout concerns for lagoons consists of the quantity and kind of wastewater to be dealt with and the extent of remedy required through regulations.
Wastewater leaving a lagoon may also require extra remedy, or "polishing," to dispose of disease-inflicting organisms or vitamins from the wastewater earlier than it may be back to the environment. If floor implemented to vegetation or grassland in Indiana, a land software allow is wanted from the Indiana Department of Environmental Management.
There are numerous one-of-a-kind phrases for lagoons. For example, the phrases lagoon and pond are regularly used interchangeably, and names, inclusive of polishing, stabilization, and maturation, can consult with a lagoon's precise position in remedy. This may be very puzzling for network leaders and owners looking to examine lagoon structures.
The phrase anaerobic means "without oxygen", which describes the situations interior this kind of lagoon. Anaerobic lagoons are most customarily used to deal with animal wastes from dairies and pig farms, industrial or commercial wastes, or because the first remedy step in structures the usage of or greater lagoons in a series.
Typically, anaerobic lagoons are designed to preserve and deal with wastewater from 20 to one hundred fifty days. They are pretty deep (generally eight to fifteen feet) and paintings just like septic tanks. Inside an anaerobic lagoon, solids withinside the wastewater separate and settle into layers. The pinnacle layer includes grease, scum, and different floating materials. If now no longer preceded with septic tanks, the layer of sludge that settles at the lowest of an anaerobic lagoon finally accumulates and need to be removed.
The wastewater that leaves an anaerobic lagoon would require in addition remedy. Odor may be a trouble with anaerobic lagoons. However, in lots of instances scent may be controlled via a whole lot of methods, inclusive of including sodium nitrate, recirculating pond effluent, and via normal maintenance.
Q10) Explain advantages & disadvantages of aerated lagoons
A10)
Advantages:
Lagoon structures may be cost-powerful to layout and assemble in regions in which land is inexpensive. They use much less strength than maximum waste water remedy methods.
They are easy to function and hold and typically require best part-time stuff. They can cope with intermittent use and surprise loadings higher than many structures, making them a great alternative for campgrounds, resorts, and different seasonal properties.
They are very powerful at putting off disease-inflicting organisms (pathogens) from wastewater. The effluent from lagoon structures may be appropriate for irrigation (in which appropriate), due to its high-nutrient and occasional pathogen content.
Disadvantages:
Lagoon structures require extra land than different remedy methods. They are much less green in bloodless climates and might require extra land or longer detention instances in those areas.
Odor can come to be a nuisance at some point of algal blooms or with anaerobic lagoons and lagoons which are inadequately maintained. Unless they're belongings maintained, lagoons can offer a breeding place for mosquitoes and different insects. They aren't very powerful at eliminating heavy metals from waste water.
Effluent from a few kinds of lagoons Contains algae and frequently calls for extra remedy or sharpening to fulfill discharge standards.
Q11) Explain design of aerated lagoon.
A11)
It is very difficult to precisely assess the quantity of water demanded by the public, since there are many variable factors affecting water consumption. The various types of water demands, which a city may have, may be broken into following classes:
Water Consumption for Various Purposes:
| Types of Consumption | Normal Range (lit/capita/day) | Average | % |
1 | Domestic Consumption | 65-300 | 160 | 35 |
2 | Industrial and Commercial Demand | 45-450 | 135 | 30 |
3 | Public Uses including Fire Demand | 20-90 | 45 | 10 |
4 | Losses and Waste | 45-150 | 62 | 25 |
Fire Fighting Demand:
The per capita fire demand is very less on an average basis but the rate at which the water is required is very large. The rate of fire demand is sometimes traeted as a function of population and is worked out from following empirical formulae:
| Authority | Formulae (P in thousand) | Q for 1 lakh Population) |
1 | American Insurance Association | Q (L/min)=4637 P (1-0.01 P) | 41760 |
2 | Kuchling's Formula | Q (L/min)=3182 P | 31800 |
3 | Freeman's Formula | Q (L/min)= 1136.5(P/5+10) | 35050 |
4 | Ministry of Urban Development Manual Formula | Q (kilo liters/d)=100 P for P>50000 | 31623 |
Q12) What is constructed wetlands?
A12)
A built wetland is a natural wastewater remedy machine that mimics and improves the effectiveness of the approaches that assist to purify water just like evidently happening wetlands. The machine makes use of water, aquatic plants (i.e.: reeds, duckweed), evidently happening microorganisms and a bed (typically of sand, soils and/or gravel).
Constructed wetlands may be used for both secondary or tertiary wastewater remedy. Many distinct designs exist together with vertical wetlands, which require much less land, however extra power for operations like pumping or siphoning than horizontal wetlands, that may rather rely upon gravity and topography.
The tremendous alternatives in layout, substances and generation permit the built wetland to be tailored to nearby situations and land availability. Costs are depending on the fee of land and substances, however in which land is inexpensive and broadly available, built wetlands are a completely cost-powerful approach of wastewater remedy. The popular idea is that the plants, microorganisms and substrates collectively act as a purification machine. First, water is slowed because it enters the wetland, taking into consideration the sedimentation of solids. Through the system of water waft via the built wetland, plant roots and the substrate put off the bigger debris gift withinside the wastewater.
Pollutants and vitamins gift withinside the wastewater are then evidently damaged down and brought up through the micro organism and plants, thereby disposing of them from the water.
The retention time withinside the wetland, which varies relying at the layout and favored high-satisfactory level, together with UV radiation and plant secretion of antibiotics may also kill the pathogens found in wastewater. After remedy in a built wetland, water may be thoroughly launched into floor waters or used diverse purposes.
Q13) What is phytoremediation?
A13)
Phytoremediation is a bioremediation technique that makes use of numerous varieties of flowers to remove, transfer, stabilize, and/or spoil contaminants withinside the soil and groundwater.
There are numerous exclusive varieties of phytoremediation mechanisms. These are:
1. Rhizosphere biodegradation. In this technique, the plant releases herbal materials through its roots, offering vitamins to microorganisms withinside the soil. The microorganisms beautify organic degradation.
2. Phyto-stabilization. In this technique, chemical substances produced via way of means of the plant immobilize contaminants, as opposed to degrade them.
3. Phyto-accumulation (additionally known as phyto-extraction). In this technique, plant roots sorb the contaminants in conjunction with different vitamins and water. The contaminant mass isn't destroyed however finally ends up withinside the plant shoots and leaves. This approach is used in the main for wastes containing metals.
At one demonstration site, water-soluble metals are taken up via way of means of plant species decided on for his or her cappotential to soak up huge portions of lead (Pb). The metals are saved withinside the plantÍs aerial shoots, that are harvested and both smelted for ability metallic recycling/restoration or are disposed of as a unsafe waste. As a popular rule, with no trouble bioavailable metals for plant uptake consist of cadmium, nickel, zinc, arsenic, selenium, and copper. Moderately bioavailable metals are cobalt, manganese, and iron. Lead, chromium, and uranium aren't very bioavailable. Lead may be made a whole lot greater bioavailable via way of means of the addition of chelating marketers to soils. Similarly, the supply of uranium and radio-cesium 137 may be more suitable the usage of citric acid and ammonium nitrate, respectively.
4. Hydroponic Systems for Treating Water Streams (Rhizofiltration). Rhizofiltration is just like phyto-accumulation, however the flowers used for cleanup are raised in greenhouses with their roots in water.
This device may be used for ex-situ groundwater treatment. That is, groundwater is pumped to the floor to irrigate those flowers. Typically hydroponic structures make use of an synthetic soil medium, along with sand combined with perlite or vermiculite. As the roots grow to be saturated with contaminants, they're harvested and disposed of.
5. Phyto-volatilization. In this technique, flowers soak up water containing natural contaminants and launch the contaminants into the air through their leaves.
6. Phyto-degradation. In this technique, flowers really metabolize and spoil contaminants inside plant tissues.
7. Hydraulic Control. In this technique, timber in a roundabout way remediate via way of means of controlling groundwater movement. Trees act as herbal pumps whilst their roots attain down in the direction of the water desk and set up a dense root mass that takes up huge portions of water. A poplar tree, for example, pulls out of the floor 30 gallons of water according to day, and a cottonwood can soak up as much as 350 gallons according to day.
Q14) Explain root zone technology.
A14)
Rootzone /Reed bed/ Constructed wetlands:
The root zone/ plant is a organic, wherein the organic remedy of waste water takes location in a soil volume, that is penetrated via way of means of roots.
The root community consists via way of means of appropriate plant species, it's far even useful if the choicest kinds of those species are selected. This shape means that the waste water flows. During the waste water flow, the nutrient factors and metals- are sure to the soil colloids respectively launched to the environment via nitrification and denitrification.
The turnover of the natural materials takes place with help from a diverse, cardio and anaerobic, microbial interest withinside the soil The cardio interest is provided with oxygen from the plant roots in addition to through the floor of the system. Thus, cardio interest is focused close to the plant roots, whilst anaerobic interest prevails in far from the roots.
This mosaic of cardio and anaerobic wallet gives choicest situations for a huge variety of lively microbial organisms. Aerobic in addition to anaerobic corporations of organisms are required for the specified down-damage of the waste water materials and can be in comparison with the anaerobic and cardio steps in a organic waste water remedy system.
In organic remedy plants, the 2 methods are usually separated. In the foundation zone/system, the above mosaic shape allows all methods to arise withinside the identical soil volume.
Q15) Give advantages of root zone technology.
A15)
Advantages
(i) Capital price worried is similar or decrease relying upon the topography of web website online and kind of soil available.
(ii) Construction of mattress is easy and entails no mechanical and electric equipment.
(iii) System calls for very little maintenance.
(iv) It is a sturdy technique and is capable of resist huge version of working conditions.
(v) It offers a regular nice of dealt with water.
(vi) It has a capability for hen sanctuary and flora and fauna habitat.
(vii) Regardless of application (municipal wastewater, mine drainage or others) the gadget has a capability to become a lovely landscape.
(viii) It may be utilised for huge variety of natural and inorganic contents withinside the effluent.
(ix) It may be set up economically for capacities as little as 1 m3/day to 10,000 m3/day and for COD enter as excessive as 50000 to 60000 mg/l.
(x) Lasts for extra than 50 to 60 years with none primary maintenance.
(xi) It can deal with effluents of huge variety of contaminants starting from sewage to distillery spent wash.
(xii) There isn't any manufacturing of sludge withinside the gadget.
(xiii) It does now no longer require professional operators.
Unit - 4
Secondary Treatment: Aerobic Suspended and Attach Growth
Q1) What is Secondary Treatment?
A1)
Secondary remedy is the elimination of biodegradable natural be counted (in answer or suspension) from sewage or comparable styles of wastewater. The goal is to obtain a positive diploma of effluent best in a sewage remedy plant appropriate for the meant disposal or reuse option.
A "number one remedy" step frequently precedes secondary remedy, wherein bodily segment separation is used to take away settleable solids. During secondary remedy, organic tactics are used to take away dissolved and suspended natural be counted measured as biochemical oxygen demand (BOD). These tactics are executed with the aid of using microorganisms in a controlled cardio or anaerobic method relying at the remedy technology.
Bacteria and protozoa devour biodegradable soluble natural contaminants (e.g. Sugars, fats, and natural short-chain carbon molecules from human waste, meals waste, soaps and detergent) at the same time as reproducing to shape cells of organic solids. Secondary remedy is broadly utilized in sewage remedy and is likewise relevant to many agricultural and commercial wastewaters. Secondary remedy structures are labeled as fixed-movie or suspended-boom structures, and as cardio as opposed to anaerobic.
Fixed-movie or connected boom structures consist of trickling filters, built wetlands, bio-towers, and rotating organic contactors, in which the biomass grows on media and the sewage passes over its surface. The fixed-movie precept has similarly advanced into transferring mattress biofilm reactors (MBBR) and Integrated Fixed-Film Activated Sludge (IFAS) tactics.
Suspended-boom structures consist of activated sludge, that is an cardio remedy machine, primarily based totally at the renovation and recirculation of a complicated biomass composed of micro-organisms (micro organism and protozoa) capable of take in and adsorb the natural be counted carried withinside the wastewater. Constructed wetlands also are being used.
An instance for an anaerobic secondary remedy machine is the upflow anaerobic sludge blanket reactor. Fixed-movie structures are greater capable of address drastic modifications in the quantity of organic fabric and might offer better elimination prices for natural fabric and suspended solids than suspended boom structures. Most of the cardio secondary remedy structures consist of a secondary clarifier to settle out and separate organic floc or fabric grown withinside the secondary remedy bioreactor.
Q2) Explain Aerobic Suspended Growth
A2)
Aerobic suspended boom remedy procedures encompass activated sludge procedures, sequencing batch reactors (SBR), and aerated lagoons. Owing to the traits of the wastewater, the touch time among the natural wastes and the microorganisms have to be better than that for home wastewater.
Processes with better hydraulic retention time (HRT) and solids retention time (SRT), together with prolonged aeration and aerated lagoon, are advocated to be used. O'Shaughnessy et al. Mentioned that cardio lagoons with extent of 267,800 gallons every had been used to deal with a wastewater from a Coca Cola bottling company. Detention time turned into 30 days; the layout glide turned into 20,000 gpd.
A collection of operational troubles befell withinside the early phase, inclusive of a caustic spill incident, non-stop clogging of air diffusers, and terrible effluent first-class because of surprise loading (e.g., liquid sugar spill). Failure to satisfy effluent requirements turned into a severe hassle withinside the remedy plant. It turned into determined that the effluent BOD5 and COD had been above one hundred and 500 mg/L, respectively.
This hassle, however, turned into solved via way of means of addition of potassium; the effluent BOD5 reduced to 60 mg/L. Tebai and Hadjivassilis used a cardio technique to deal with smooth drink wastewater with a everyday glide of 560 m3/day, BOD5 of 564 mg/L, and TSS of 580 mg/L. Before starting organic remedy, the wastewater turned into first dealt with via way of means of bodily and chemical remedy procedures. The bodily remedy covered screening and influent equalization; withinside the chemical remedy, pH adjustment turned into finished accompanied via way of means of the conventional coagulation/flocculation technique.
A BOD5 and COD elimination of 43.2 and 52.4%, respectively, turned into executed withinside the bodily and chemical remedy procedures. In the organic remedy, the BOD5 loading fee and the sludge loading fee had been 1.sixty four kg BOD5/day m3 and 0.forty two kg BOD5/kg MLSS day; the BOD5 and COD elimination efficiencies had been sixty four and 70%, respectively. The organic remedy turned into operated at a high-fee mode, which turned into the principle purpose for the decrease elimination efficiencies of BOD5 and COD.
Q3) Write a short note on Attach Growth
A3)
Wastewater remedy methods wherein the microorganisms and micro organism treating the wastes are connected to the media withinside the reactor. The wastes being dealt with float over the media.
Trickling filters and rotating organic contactors are connected boom reactors. These reactors may be used for BOD removal, nitrification, and denitrification. Wastewater remedy methods wherein the microorganisms and micro organism treating the wastes are suspended withinside the wastewater being dealt with. The wastes float round and via the suspended growths.
The numerous modes of the activated sludge technique employ suspended boom reactors. These reactors may be used for BOD (biochemical oxygen demand) removal, nitrification, and denitrification. Most micro-organisms can colonise the floor of a substrate while they may be on the boom stage. Bacteria connect themselves to the substrate by using the exopolymers they produce. The preliminary colonisation of a stable takes location on some of preferential webweb sites and it's miles from those webweb sites that the biofilm develops till the full floor region of the substrate is coated.,
At the equal time, new cells are produced and motive the movie to thicken. The oxygen and vitamins carried withinside the water to be dealt with diffuse via the movie till it achieves a thickness such that oxygen now not reaches the inner most mobileular layers. Thus, stratification happens in thick movies with the superimposition of an cardio layer inside which the oxygen diffuses and a deeper anaerobic layer that consists of no oxygen.
Q4) What is suspended growth system?
A4)
The activated sludge procedure is a cardio suspended-boom procedure that keeps a pretty excessive populace of microorganisms (biomass) through recycling settled biomass again to the remedy procedure. The biomass converts soluble and colloidal biodegradable natural count number and a few inorganic compounds into mobileular mass and metabolic quit products.
The biomass is separated from the wastewater through settling in a clarifier for recycling or losing to sludge dealing with processes. Preliminary remedy to do away with settleable solids and floatable substances is typically furnished through a septic tank or different number one remedy device.
Most onsite designs are able to imparting substantial ammonia oxidation and powerful elimination of natural count number. The primary machine includes some of interrelated components - An aeration tank or basin. - An oxygen supply and system to disperse atmospheric or pressurized air or oxygen into the aeration tank at a price enough to constantly preserve high-quality dissolved oxygen. - A manner to as it should be blend the aeration basin and make certain suspension of the biomass (typically achieved through the aeration machine). - A clarifier to split the biomass from the handled effluent and acquire settled biomass for recycling to the aeration basin.
Fig: Suspended growth system
These structures are commonly preceded with the aid of using a septic tank and accompanied with the aid of using a subsurface wastewater infiltration device (SWIS). Despite a few claims of decreased SWIS sizing while as compared to the traditional septic tank pretreatment, the clothier is counseled to don't forget floor water protection.
These structures have to be implemented simplest wherein onsite device control offerings are available. For floor water discharge, the device should be accompanied with the aid of using disinfection at a minimal to constantly meet discharge standards.
However, a few subsurface (non-human-contact) reuse can be applied without similarly treatment. High biomass structures may be a low-fee approach of upgrading present overloaded CFSGAS devices that presently do now no longer meet BOD or nitrification goals. They also can compete immediately with traditional designs due to the fact they've extra balance in coping with particularly variable loadings.
Q5) What is oxidation pond?
A5)
Oxidation ponds, additionally referred to as lagoons or stabilization ponds, are big, shallow ponds designed to deal with wastewater via the interplay of sunlight, micro organism, and algae.
Algae develop the use of electricity from the solar and carbon dioxide and inorganic compounds launched via way of means of micro organism in water. During the manner of photosynthesis, the algae launch oxygen wished via way of means of cardio micro organism.
Mechanical aerators are once in a while mounted to deliver but greater oxygen, thereby lowering the desired length of the pond. Sludge deposits withinside the pond ought to finally be eliminated via way of means of dredging. Algae ultimate withinside the pond effluent may be eliminated via way of means of filtration or via way of means of a mixture of chemical remedy and settling. In this remedy gadget a sequence of big plastic disks established on a horizontal shaft are partly submerged in number one effluent.
As the shaft rotates, the disks are uncovered alternately to air and wastewater, permitting a layer of micro organism to develop at the disks and to metabolize the organics withinside the wastewater.
For the elimination of extra suspended solids and BOD from secondary effluent, effluent sprucing is an powerful remedy. It is most customarily completed the use of granular media filters, just like the filters used to purify ingesting water. Polishing filters are generally constructed as prefabricated units, with tanks located at once above the filters for storing backwash water. Effluent sprucing of wastewater will also be performed the use of microstrainers of the kind utilized in treating municipal water supplies.
Q6) Explain Bacteria – algae symbiosis
A6)
Symbiosis of micro organism-animals: Bacteria are recognized to be very not unusualplace endo and ectosymbiotic microorganisms of humans, bugs and different animals.
All humans accumulate unique micro organism on the beginning as ordinary flowers which stay related during the existence span. Animals which includes farm animals additionally undergo unique micro organism as resident microflora. Normal flowers micro organism connect and colonize epithelial mucus lining of organs of gastrointestinal, genitourinary and respiration tract of animals and humans.
They constitute mutualism in addition to commensalism with the host. Normal flowers gets defensive environment, vitamins and delivery from host even as as host receives deliver of positive B vitamins, improvement and activation of immune gadget and safety from pathogenic microbes. Lactobacilli living in vagina produce lactic acid which protects girl genitourinary tract from infectious yeasts like Candida and different pathogenic microbes.
Rumen micro organism which includes Propionibacterium spp. Living in farm animals gut are cellulolytic and in fact digest cellulosic meals ingested with the aid of using animal; farm animals do not produce other approach of cellulose usage and cellulosic content material of vegetable count could in any other case not possible to degrade without useful resource with the aid of using rumen micro organism. Cooperative interplay among aphids and micro organism Buchnera aphidicola is one of the fine instance of insect and bacterial symbiosis.
Bacteria offer all enzymes vital for the synthesis of vital amino acids which might be missing in aphid meals (plant sap); in go back aphids synthesize enzymes required to accumulate bacterial mobileular wall. Another instance of micro organism-animal symbiosis is of gutless worms of deep hydrothermal vents.
They have sulfur oxidizing micro organism as endosymbionts; due to the fact that they do not have digestive tract, they may be absolutely depending on vitamins supplied with the aid of using those micro organism.
Association of squids, jelly fish and fishes like angler fish and lantern fish with luminescent micro organism is thrilling instance of symbiotic interplay. Bioluminescence is obtained with the aid of using luminescent micro organism like Vibrio fischeri which harbor within the mild organs of those animals; it's miles very beneficial for area of prey, as course finder in deep sea regions, to draw mate or to warn off or repel the predators.
Q7) Give advantages & disadvantages of oxidation ponds
A7)
Advantages:
The stabilization pond reduces the organic oxygen call for as much as 90% naturally.
It is a easy technique to perform or does now no longer require state-of-the-art equipment.
Oxidation pond is a realistic and powerful technique for the wastewater remedy of home and change wastes in tropical areas.
The operation of a stabilization pond does now no longer require a great deal labour-power.
It is a cost-effective technique for the remedy of wastewater from small and remoted units.
The oxidation pond remedy system is natural, as it makes use of microorganisms including micro organism and algae.
This makes the approach of remedy cost-powerful in phrases of its construction, maintenance, and strength requirements.
Oxidation ponds also are productive, as it generates effluent that may be used for different applications. Finally, oxidation ponds may be taken into consideration a sustainable approach for remedy of wastewater.
Disadvantages:
The creation of a stabilization pond calls for greater land area.
The upkeep is pretty intricate. Sometimes, it offers a bad odor and mosquito threat in the course of the technique if now no longer correctly maintained.
There may also get a danger of effluent seepage into the floor water, that can in the end purpose floor water pollution.
Q8) What are aerated lagoons?
A8)
An aerated lagoon (or aerated pond) is a easy wastewater remedy gadget including a pond with synthetic aeration to sell the organic oxidation of wastewaters.
There are many different cardio organic approaches for remedy of wastewaters, as an instance activated sludge, trickling filters, rotating organic contactors and biofilters.
They all have in not unusualplace the usage of oxygen (or air) and microbial movement to lessen the pollution in wastewaters. Suspension combined lagoons, wherein there's much less electricity supplied through the aeration gadget to maintain the sludge in suspension.
Facultative lagoons, wherein there's inadequate electricity supplied through the aeration gadget to maintain the sludge in suspension and solids settle to the lagoon ground. The biodegradable solids withinside the settled sludge then degrade as in an anaerobic lagoon.
Suspension combined lagoons go with the drift via activated sludge structures wherein the effluent has the identical composition because the combined liquor withinside the lagoon.
Typically the sludge may have a house time or sludge age of one to five days. This way that the chemical oxygen demand (COD) eliminated is enormously little and the effluent is consequently unacceptable for discharge into receiving waters.
The goal of the lagoon is consequently to behave as a biologically assisted flocculator which converts the soluble biodegradable organics withinside the influent to a biomass that is capable of settle as a sludge. Usually the effluent is then installed a 2nd pond wherein the sludge can settle.
The effluent can then be eliminated from the pinnacle with a low COD, whilst the sludge accumulates at the ground and undergoes anaerobic stabilisation.
Q9) What is the principle of aerated lagoon?
A9)
Lagoons are pond-like our bodies of water or basins designed to receive, preserve, and deal with wastewater for a predetermined length of time. If necessary, they're coated with material, inclusive of clay or a synthetic liner, to save you leaks to the groundwater below.
In the lagoon, wastewater is dealt with via a aggregate of physical, biological, and chemical processes. Much of the remedy takes place naturally, however a few structures use aeration gadgets to feature oxygen to the wastewater. Aeration makes remedy greater efficient, in order that much less land place is necessary. Aerators may be used to permit present structures to deal with greater wastewater.
Lagoons need to be in my view designed to in shape a particular use. Designs are primarily based totally on such elements as kind of soil, quantity of land place available, and climate. A critical layout concerns for lagoons consists of the quantity and kind of wastewater to be dealt with and the extent of remedy required through regulations.
Wastewater leaving a lagoon may also require extra remedy, or "polishing," to dispose of disease-inflicting organisms or vitamins from the wastewater earlier than it may be back to the environment. If floor implemented to vegetation or grassland in Indiana, a land software allow is wanted from the Indiana Department of Environmental Management.
There are numerous one-of-a-kind phrases for lagoons. For example, the phrases lagoon and pond are regularly used interchangeably, and names, inclusive of polishing, stabilization, and maturation, can consult with a lagoon's precise position in remedy. This may be very puzzling for network leaders and owners looking to examine lagoon structures.
The phrase anaerobic means "without oxygen", which describes the situations interior this kind of lagoon. Anaerobic lagoons are most customarily used to deal with animal wastes from dairies and pig farms, industrial or commercial wastes, or because the first remedy step in structures the usage of or greater lagoons in a series.
Typically, anaerobic lagoons are designed to preserve and deal with wastewater from 20 to one hundred fifty days. They are pretty deep (generally eight to fifteen feet) and paintings just like septic tanks. Inside an anaerobic lagoon, solids withinside the wastewater separate and settle into layers. The pinnacle layer includes grease, scum, and different floating materials. If now no longer preceded with septic tanks, the layer of sludge that settles at the lowest of an anaerobic lagoon finally accumulates and need to be removed.
The wastewater that leaves an anaerobic lagoon would require in addition remedy. Odor may be a trouble with anaerobic lagoons. However, in lots of instances scent may be controlled via a whole lot of methods, inclusive of including sodium nitrate, recirculating pond effluent, and via normal maintenance.
Q10) Explain advantages & disadvantages of aerated lagoons
A10)
Advantages:
Lagoon structures may be cost-powerful to layout and assemble in regions in which land is inexpensive. They use much less strength than maximum waste water remedy methods.
They are easy to function and hold and typically require best part-time stuff. They can cope with intermittent use and surprise loadings higher than many structures, making them a great alternative for campgrounds, resorts, and different seasonal properties.
They are very powerful at putting off disease-inflicting organisms (pathogens) from wastewater. The effluent from lagoon structures may be appropriate for irrigation (in which appropriate), due to its high-nutrient and occasional pathogen content.
Disadvantages:
Lagoon structures require extra land than different remedy methods. They are much less green in bloodless climates and might require extra land or longer detention instances in those areas.
Odor can come to be a nuisance at some point of algal blooms or with anaerobic lagoons and lagoons which are inadequately maintained. Unless they're belongings maintained, lagoons can offer a breeding place for mosquitoes and different insects. They aren't very powerful at eliminating heavy metals from waste water.
Effluent from a few kinds of lagoons Contains algae and frequently calls for extra remedy or sharpening to fulfill discharge standards.
Q11) Explain design of aerated lagoon.
A11)
It is very difficult to precisely assess the quantity of water demanded by the public, since there are many variable factors affecting water consumption. The various types of water demands, which a city may have, may be broken into following classes:
Water Consumption for Various Purposes:
| Types of Consumption | Normal Range (lit/capita/day) | Average | % |
1 | Domestic Consumption | 65-300 | 160 | 35 |
2 | Industrial and Commercial Demand | 45-450 | 135 | 30 |
3 | Public Uses including Fire Demand | 20-90 | 45 | 10 |
4 | Losses and Waste | 45-150 | 62 | 25 |
Fire Fighting Demand:
The per capita fire demand is very less on an average basis but the rate at which the water is required is very large. The rate of fire demand is sometimes traeted as a function of population and is worked out from following empirical formulae:
| Authority | Formulae (P in thousand) | Q for 1 lakh Population) |
1 | American Insurance Association | Q (L/min)=4637 P (1-0.01 P) | 41760 |
2 | Kuchling's Formula | Q (L/min)=3182 P | 31800 |
3 | Freeman's Formula | Q (L/min)= 1136.5(P/5+10) | 35050 |
4 | Ministry of Urban Development Manual Formula | Q (kilo liters/d)=100 P for P>50000 | 31623 |
Q12) What is constructed wetlands?
A12)
A built wetland is a natural wastewater remedy machine that mimics and improves the effectiveness of the approaches that assist to purify water just like evidently happening wetlands. The machine makes use of water, aquatic plants (i.e.: reeds, duckweed), evidently happening microorganisms and a bed (typically of sand, soils and/or gravel).
Constructed wetlands may be used for both secondary or tertiary wastewater remedy. Many distinct designs exist together with vertical wetlands, which require much less land, however extra power for operations like pumping or siphoning than horizontal wetlands, that may rather rely upon gravity and topography.
The tremendous alternatives in layout, substances and generation permit the built wetland to be tailored to nearby situations and land availability. Costs are depending on the fee of land and substances, however in which land is inexpensive and broadly available, built wetlands are a completely cost-powerful approach of wastewater remedy. The popular idea is that the plants, microorganisms and substrates collectively act as a purification machine. First, water is slowed because it enters the wetland, taking into consideration the sedimentation of solids. Through the system of water waft via the built wetland, plant roots and the substrate put off the bigger debris gift withinside the wastewater.
Pollutants and vitamins gift withinside the wastewater are then evidently damaged down and brought up through the micro organism and plants, thereby disposing of them from the water.
The retention time withinside the wetland, which varies relying at the layout and favored high-satisfactory level, together with UV radiation and plant secretion of antibiotics may also kill the pathogens found in wastewater. After remedy in a built wetland, water may be thoroughly launched into floor waters or used diverse purposes.
Q13) What is phytoremediation?
A13)
Phytoremediation is a bioremediation technique that makes use of numerous varieties of flowers to remove, transfer, stabilize, and/or spoil contaminants withinside the soil and groundwater.
There are numerous exclusive varieties of phytoremediation mechanisms. These are:
1. Rhizosphere biodegradation. In this technique, the plant releases herbal materials through its roots, offering vitamins to microorganisms withinside the soil. The microorganisms beautify organic degradation.
2. Phyto-stabilization. In this technique, chemical substances produced via way of means of the plant immobilize contaminants, as opposed to degrade them.
3. Phyto-accumulation (additionally known as phyto-extraction). In this technique, plant roots sorb the contaminants in conjunction with different vitamins and water. The contaminant mass isn't destroyed however finally ends up withinside the plant shoots and leaves. This approach is used in the main for wastes containing metals.
At one demonstration site, water-soluble metals are taken up via way of means of plant species decided on for his or her cappotential to soak up huge portions of lead (Pb). The metals are saved withinside the plantÍs aerial shoots, that are harvested and both smelted for ability metallic recycling/restoration or are disposed of as a unsafe waste. As a popular rule, with no trouble bioavailable metals for plant uptake consist of cadmium, nickel, zinc, arsenic, selenium, and copper. Moderately bioavailable metals are cobalt, manganese, and iron. Lead, chromium, and uranium aren't very bioavailable. Lead may be made a whole lot greater bioavailable via way of means of the addition of chelating marketers to soils. Similarly, the supply of uranium and radio-cesium 137 may be more suitable the usage of citric acid and ammonium nitrate, respectively.
4. Hydroponic Systems for Treating Water Streams (Rhizofiltration). Rhizofiltration is just like phyto-accumulation, however the flowers used for cleanup are raised in greenhouses with their roots in water.
This device may be used for ex-situ groundwater treatment. That is, groundwater is pumped to the floor to irrigate those flowers. Typically hydroponic structures make use of an synthetic soil medium, along with sand combined with perlite or vermiculite. As the roots grow to be saturated with contaminants, they're harvested and disposed of.
5. Phyto-volatilization. In this technique, flowers soak up water containing natural contaminants and launch the contaminants into the air through their leaves.
6. Phyto-degradation. In this technique, flowers really metabolize and spoil contaminants inside plant tissues.
7. Hydraulic Control. In this technique, timber in a roundabout way remediate via way of means of controlling groundwater movement. Trees act as herbal pumps whilst their roots attain down in the direction of the water desk and set up a dense root mass that takes up huge portions of water. A poplar tree, for example, pulls out of the floor 30 gallons of water according to day, and a cottonwood can soak up as much as 350 gallons according to day.
Q14) Explain root zone technology.
A14)
Rootzone /Reed bed/ Constructed wetlands:
The root zone/ plant is a organic, wherein the organic remedy of waste water takes location in a soil volume, that is penetrated via way of means of roots.
The root community consists via way of means of appropriate plant species, it's far even useful if the choicest kinds of those species are selected. This shape means that the waste water flows. During the waste water flow, the nutrient factors and metals- are sure to the soil colloids respectively launched to the environment via nitrification and denitrification.
The turnover of the natural materials takes place with help from a diverse, cardio and anaerobic, microbial interest withinside the soil The cardio interest is provided with oxygen from the plant roots in addition to through the floor of the system. Thus, cardio interest is focused close to the plant roots, whilst anaerobic interest prevails in far from the roots.
This mosaic of cardio and anaerobic wallet gives choicest situations for a huge variety of lively microbial organisms. Aerobic in addition to anaerobic corporations of organisms are required for the specified down-damage of the waste water materials and can be in comparison with the anaerobic and cardio steps in a organic waste water remedy system.
In organic remedy plants, the 2 methods are usually separated. In the foundation zone/system, the above mosaic shape allows all methods to arise withinside the identical soil volume.
Q15) Give advantages of root zone technology.
A15)
Advantages
(i) Capital price worried is similar or decrease relying upon the topography of web website online and kind of soil available.
(ii) Construction of mattress is easy and entails no mechanical and electric equipment.
(iii) System calls for very little maintenance.
(iv) It is a sturdy technique and is capable of resist huge version of working conditions.
(v) It offers a regular nice of dealt with water.
(vi) It has a capability for hen sanctuary and flora and fauna habitat.
(vii) Regardless of application (municipal wastewater, mine drainage or others) the gadget has a capability to become a lovely landscape.
(viii) It may be utilised for huge variety of natural and inorganic contents withinside the effluent.
(ix) It may be set up economically for capacities as little as 1 m3/day to 10,000 m3/day and for COD enter as excessive as 50000 to 60000 mg/l.
(x) Lasts for extra than 50 to 60 years with none primary maintenance.
(xi) It can deal with effluents of huge variety of contaminants starting from sewage to distillery spent wash.
(xii) There isn't any manufacturing of sludge withinside the gadget.
(xiii) It does now no longer require professional operators.