Wastewater Treatment and Reclamation †Free Samples to Students

Question: Discuss about the Wastewater Treatment and Reclamation. Answer: Introduction: Recycling wastewater means that it is the same water that is used hence water from other areas is not utilized. In places where there is plenty of fresh water normally suffer when their water is taken hence recycling water will it only ensure that their water is maintained but also environmental sustainability is promoted(Bonomo, 2011, p. 535). In most cases, the process of recycling water inhibits its removal from delicate ecosystems and also prevents the wastewater from polluting other water bodies such as seas or oceans. This process ensures that the waste water such as sewage is treated and reutilized thereby the saving the aquatic life from pollution(Partners, 2012, p. 430). Increases Irrigation Benefits According to EPA recycled water contains best properties such as high levels of nitrogen which are of high benefit to irrigation systems(Hamidi Abdul Aziz, 2014, p. 332). Improved Wetlands There a lot of being benefits derived from the wetlands including accommodating wildlife, sustaining the aquatic life, improving water quality and lessening of floods, according to the EPA. The addition of recycled water to dried wetlands helps in sustaining their survival. Provides Future Water Supply Recycling wastewater ensures that there is absolutely hope of water by the future generation. Reduced transportation costs Industries that produce a high volume of wastewater find it difficult in transporting it hence recycling the wastewater will greatly eliminate the costs incurred when transporting the wastewater. Additionally, there will also be a reduction in demand for new water sources since there will be plenty of readily available treated wastewater(Kurbiel, 2009, p. 978). Lower Operation Costs Besides, the repeated use of recycled wastewater is comparatively cheaper as compared to the use fresh water. Else, using fresh water also slowly eliminates the freshwater bodies rendering them obsolete and polluted. Treatment Process This system will function based on the physical principles, chemical and biological principles to eliminate the pollutants from the water. Hence it will entail three stages namely; primary treatment, secondary treatment and finally the tertiary treatment process or the advanced treatment(Kurbiel, 2009, p. 432). There are various strategies which have been put into place at each and every stage to ensure that the water is of high quality as described below. Primary Treatment This stage utilizes simple and sustainable mechanical and biological processes to eliminate the first half of the pollutants present in the wastewater. It comprises of bar screens, grit chamber and the primary clarification. Bar screens These are screens which are mechanical in nature and they are responsible for eliminating larger particles or instance plastic rags, rocks etc. There is the presence of a rake placed horizontally on a ragged gear drive which takes the captured wastes to a conveyor which in turn places the wastes into a dumpster for exclusion(Partners, 2012, p. 909). Grit chamber In this section, the flowing wastewater enters this chamber which is aerated to allow fine grit particles to settle. Primary clarification After the water passes through the grit chamber, it is allowed into the primary clarifies which regulates the speed of the water flow to allow bigger particles to settle. These particles then are digested and dried for useful purposes such as composting(Partners, 2012, p. 434). At the end of the primary treatment, the quality of water is a bit increased and can be quantifiable be graded at 20%. Secondary treatment This stage uses biological means of eliminating the remaining pollutants. It has the following sections; aeration basins and the final clarifiers Aeration basins The wastewater is allowed to the aeration basins which helps in mixing the water with oxygen. The bacterial microorganisms present then take in the organic material. The microorganisms convert solids that have not settled to a form that they easily settle and thereafter they get absorbed in the final clarifiers as bio solids(Russell L. Culp, 2011, p. 754). Final Clarifiers At this stage, the solids which are still remaining settle here and get digested, however, some are taken back to the aeration chamber to be released into the incoming wastewater. At the end of the primary treatment, the quality of water is a bit increased and can be quantifiable be graded at 71%(Kurbiel, 2009, p. 843). After the primary and the secondary processes of water treatment, the water finally undergoes chemical treatment. This stage comprises of sand filters, disinfectants and DE chlorinators. Sand filters Upon leaving the secondary treatment stage, the water goes into sand filters which primarily eliminates any solids that have been left out. The advantage with this filtering system is that it can be easily observed when it is under operation. These filters are located between the disinfection chamber and the final clarifiers(Russell L. Culp, 2007, p. 444). Disinfection and DE chlorination Water from the sand filters is passed through the chlorine chambers for disinfection whereby the remaining microorganism are done away with. Thereafter, the chlorine is eliminated by the aid of sulphur dioxide since sulphur is not desirable to be present in the water bodies. At the end of the advanced treatment, the quality of water is a bit increased and can be quantifiable be graded at 93%(Skarheim, 2008, p. 783). Outfall After the whole water treatment process, the water is now clean and ready to be released into the environment. At the point where water is released into the environment is called the outfall. Solid waste processing During the treatment processes, bio solids are generated from each stage. These bio solids are very beneficial to the environment and should be decomposed. They act as natural organic fertilizer and also as soil conditioners. Besides, these bio solids can be utilized agriculturally by providing the full micronutrients and essential nutrients required by a healthy plant growth. Thus, they can be applied directly to the Land or applied in gardens and lawns as compost manure. Below are ways of processing bio solids(Skarheim, 2008, p. 498). Thickening In this chamber, air under high pressure is forced into the liquid where it gets dissolved and then it is allowed into the sludge. At the sludge, tiny air bubbles rise carrying the solids into the surface(Russell L. Culp, 2007, p. 523). Anaerobic digester Here, the sludge which has settled into the primary clarifiers is pumped in for stabilization. The air inside the tank is restricted and cannot escape at any point thereby encouraging anaerobic respiration(Skarheim, 2008, p. 436). De watering This process is meant to remove water from the digested solids. It is mechanically done using belt filter press or through squeezing. Below is the flow chart diagram Technically, Wastewater refers to the water which is combined with water materials and then released to the environment. The sources of the waste materials range widely from residential to industrial, institution and also to commercial. These wastes are harmful to the environment and also to human thus a more friendly and sustainable way should be put into place to ensure they are done away with(Kurbiel, 2009, p. 977). The whole process of wastewater treatment process involves biological, mechanical and sludge treatment process and it is done in structures called wastewater treatment plants. Assuming that the following information is provided to be used in the design of a wastewater plant; -M is the last two digits of group members when averaged and other values have been assumed as per the references and citations, the wastewater CONTAINS impurities that are big sized i.e. Bottles and hair(Steven E. Esmond, 2009, p. 852). Designing, Silt particles having a diameter and density of 0.017*(1+M*0.1) cm and 3*(1-M*0.1) g/cm3 respectively. Design a grit chamber and write down the merits of an aerated grit chamber? Solution Grit chamber: M = 5 O the particles = 0.017*(1+ M*0.1)/100 = 0.000255 m Density = 3*(1-M*0.1) = 1500 kg/m3 From introduction to environmental engineering book, the temperature of wastewater 22 degrees Celsius, while the density of density is approximately 1000 kg/m3 .besides, the viscosity is 0.995 mPa. Silt particles diameter is 0.000255 m., length of the grit chamber = 13.5m Vs. =g* {(s )*d}/18 but g =9.8, s=1500, =1000, d=0.000255m, =0.995 Hence replacing; Vs. = 9.8 (15001000)0.000255/18(0.995) = 0.0177 m/s settling velocity Reynolds number is thus calculated as shown; Re =settling velocity * silt diameter / viscosity = (0.0177)*(0.000255)/ (0.000995/1000) = 4.54 Assuming that horizontal velocity =0.25m/original velocity is Vo = 0.028 m/s, rate of flow = 0.15 m3/s, channel width= 0.56m The cross sectional area is calculated by dividing the flow rate by horizontal velocity. A = (0.15 m3/s)/ (0.25m/s) = 0.60 m2 Height of the flow is obtained by; area/channel width = 0.60/0.56 h =1.07m The time taken by the particle to reach the bottom of the chamber is evaluated by t=h/Vs. = 1.07/0.028 = 38.2 s Comparing with the total time taken by the particles in the grit chamber will use the assumed grit chamber length and horizontal velocity of 13.5 m and 0.25 m/s respectively(Russell L. Culp, 2007, p. 232). Thus, t = 13.5/0.025 = 54s, hence the particle will have no doubt be contained in the chamber Overflow velocity = 0.15/ (13.5*0.56) =19.8 mm/s Diving by the settling viscosity to obtain the ratio, Vs. /Vo = 17.7 / 19.8 = 0.893 which is less than 1. This means that particles having a diameter equal to this would settle in the bottom of the chamber. Advantages of aerated grit chamber: Below are some of the merits that come with this design of the aerated grit chamber, The effluent removal efficiency is Consistent for a longer period. The pre aeration process helps to improve downstream performance which alternatively reduces the incoming wastewater septic conditions(Steven E. Esmond, 2009, p. 500). The versatile nature of the aerated grit chambers helps in enabling the addition and mixing of chemical and also flocculation process. The maintenance cost is greatly reduced(Hamidi Abdul Aziz, 2014, p. 224). This design is very simple since there are no underwater parts that are in motion Besides, the lift pumping can be enabled by a blower The primary purpose of the equalization basin is improving the efficiency of secondary treatment and progressive treatment processes. Thus, the design will firstly involve the determination of the average flow, which is 0.1404 m3/s as can be seen from the above table. The flows are then organized starting with the time and flow which surpasses the average flow and time. I.e. t= 0900h at flow v= 0.1965m3/s. below is the table arrangement. The other columns have been generated as shown below. Volume inflow = inflow *time difference (1hour)*3600 seconds per hour Volume outflow = outflow *time difference (1hour)*3600 seconds per hour dS= inflow volume outflow volume The required volume for the equalization basin is the maximum cumulative storage. With the requirement for 25 percent excess, the volume would then be(Kurbiel, 2009, p. 522). The maximum cumulative volume/ storage would then be obtained by a 25% excess of volume i.e. =125/ 100 * 2219.4 =27774.25 m3. The average concentration is determined as. Sav= inflow volume at certain time interval * average BOD5 concentration at certain time interval + previous time interval final volume of basin water * BOD5 concentration in the basin) initial volume + settling volume. Design of the Primary sedimentation Using the following set of data, evaluate the design of the primary sedimentation with regards to the detention time, weir loading and the overflow rate. Design data. Length of the weir = 75m, Concentration of sludge = 6 %, Flow = 0.1965 m3/s., Efficiency to be achieved = 60%, Effective Length = 40 m, depth of the liquid = 2 m, Influent= 286 mg/l. Width = 10 m Detention time= tank volume / flow, = {40*10*2/ 0.1965}/ 3600 = 1.13 h which is reasonably good. The overflow rate= flow /surface area. Vo = 0.000491 x 86400 = 42.4 m/d which is reasonably good. The weir loading = flow/length of the weir = 0.00262 x 86400 = 226.368 m3/d. m which is reasonably good. Design of the secondary settling tank. Taking the average overflow rate obtained above of 42.4 m/d, the diameter of the secondary tank is first computed as shown below, Area = (0.150 86400) /42.4 = 305.66 m2 = ?D2/4 Hence the diameter is approximate D= 20 m Selecting an SWD of 3.7 m settling basin table and thus checking the solids loading, we obtain SL = 2500 0.3 ? (20)2/4 = 750/314 *10-3*86400 = 206.36 kg/d .m2. Comparing this rate with the maxima in the figure above. We can deduce that; Assuming SVI= 175 f, the extreme permissible loading is 200 kg/d .m2. The weir loading, WL = 0.15 86400 ? (20) = 206.36 m3/dm. Which is reasonably accepted since it does not exceed prescribed weir loading in GLUMRB Ways of handling sludge Sludge is basically a bio solid or residue that is responsible for the storage in sewage treatment plants and its proper handling ensures that it is properly consumed. The treatment comprises of the various process involving stabilization, dehydration, burning, absorption, and dewatering. Below are ways of handling the bio solids(Skarheim, 2008, p. 357). Agriculturally though inorganic manure production It can also be used as compost manure Landfilling Merits and drawbacks of biological phosphorus elimination process Advantages The ability of dewatering is not altered hence resulting to high-quality sludge Low content of saline is obtained The biological elimination means that no chemicals are produced during sludge production Besides, the inhabitation of nitrification process is reduced Drawbacks Some phosphorus content is released during treatment process There is Reliance on wastewater composition hence the process may not be stable at times The volume index of the sludge is influenced negatively Cost analysis: infrastructure cost maintenance cost (energy consumption) During the water treatment process, various form of energy is involved I.e. electrical, chemical and also manual. These forms can be classified as either renewable, nonrenewable or indirect form of energy. Below is the estimation of how the various forms are consumed This comes as a result of the load in the motor which is operated for a specific period of time in hours. Assuming that the motor is having an efficiency of 0.8, below will be the approximate kilowatt-hour usage for the total energy specifics. The total amount of energy consumed is found to be approximately 1.03kWh/m3 of wastewater treatment which is considerably lower than the values which are contained in the literature for large-scale wastewater treatment plants. Thus making this kind of design more adaptable Conclusion Recycled wastewater has a lot of benefits such as environmental benefits, improvement of the wetlands, lowering of the operation costs, reducing transportation costs, increasing irrigation benefits as well as providing future water supply. This project involved the design of a wastewater treatment plant address various risks as indicated above, the data used in the design have been assumed and the various stages have been designed including the secondary settling tank, grit chamber, primary sedimentation tank and the equalization basin, besides the theoretical aspects of the benefits and reason as to why the waste water treatment plant should be adopted have been well explained(Skarheim, 2008, p. 667). References Bonomo, L., 2011. Advanced Wastewater Treatment, Recycling and Reuse: Selected Proceedings of the 6th International Conference on Advanced Wastewater Treatment, Recycling and Reuse. 4th ed. Virginia: Pergamon Press. Hamidi Abdul Aziz, A. M., 2014. Wastewater Engineering: Advanced Wastewater Treatment Systems. 3rd ed. Chicago: IJSR Publications. Kurbiel, J., 2009. Advanced Wastewater Treatment and Reclamation: Proceedings of the IAWPRC Conference Held in Cracow, Poland, 2nd ed. Virginia: Pergamon Press. Partners, G., 2012. Engineering SoundBite: Advanced Wastewater Treatment. 2nd ed. Carlisle: Guyer Press. Russell L. Culp, G. L. C., 2007. Advanced wastewater treatment. 1st ed. Westminster: Van Nostrand Reinhold. Russell L. Culp, G. M. W. G. L. C., 2011. Handbook of Advanced Wastewater Treatment. 2nd ed. Michigan: Van Nostrand Reinhold. Skarheim, H. P., 2008. Biological Monitoring of an Advanced Wastewater Treatment Plant. 2nd ed. New York Hans Petter Skarheim press. Steven E. Esmond, T. A. . M. U. M. E. R. L., 2009. The removal of metals and viruses in advanced wastewater treatment sequences, Volume 1. 2nd ed. Leicester: Municipal Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency.