Methods to Achieve Waste Minimization - Assignment Example

ASSIGNMENT QUESTIONS [Name] [Professor] [Institution] [Course] [Date] Question 1 (a) From the table, the SS value of stream #4 and #5 is very high as compared to other streams. This means it is highly concentrated. Therefore, an effective scheme will involve separating #4 and #5 followed by anaerobic digestion treatment. Stream #3 has more water content. This water can be recycled in order to minimize the wastes. Stream #6 and #7 have got low SS values. This shows that it is lowly concentrated. They contain a lot of water or are dissolved in water. Some of the components in #6 and #7 should first be separated from any water content before further processing. Streams #1, 2 and 7 can be let to settle in order to segragate them from other wastes, and then subject them to further treatment. (b) The flow and the BOD concentration of the combined stream of #4 and #5. The BOD concentration of combined #4 and #5 stream is given by: = The Flow of the combined #4 and #5 stream is given by: = = = = 0.3991 L/min Question 2 The three methods used to achieve waste minimization in paper and pulp manufacturing processes. (i) By-product recovery In paper and pulp manufacturing process, by-products can be recovered throght two main methods. This includes recovery from black liquor and recovery from effluents. Black liquour gets concentrated in many stages through the procecess of evaporation. It is heated using steam until it remains with about 66% solids and then the black liquour obtained is burnt within the recovery boiler and different salts are produced in the process. Such salts include sodium sulfate, soduim carbonate and sodium sulfide. (ii) Process chemical change Bleaching in the pulping mills leads to production of COD by almost half. Therefore, in order to reduce the COD in the pulping mills, hydrogen peroxide or chlorine oxide can be used instead of ozine or chlorine bleaching. Hydrogen peroxide is very strong in both oxidizing and reducing. It does not have the environmental impacts associated with chlorine and that is why the chemical change to use hydrogen peroxide is preferable. It can reduce the yellowing of pulp. (iii) Wastewater recycling The different chemicials used in the paper industry make the paper to be colored. A lot of water and some additions are used in order to decolour the paper. Waste water is produced depending on the bleaching agents used. The waste water results from the paper machines and processes. It is treated and put back into use. Some of the methods of water treatment include reverse osmosis process. Question 3 Human Barriers of Waste Minimization (i) People’s attitudes People normally tend to waste rather than to save. Some do not know how to segregate the wastes. Negative attitude of the workers may also lead to insubordination towards waste minimization. (ii) Lack of resources A lot of knowledge, people or money are needed in order to carry out effective waste minimization. Some recycling processes need technological know-how. For instance, besides having the equipment, some knowledge is required in the operation of the reverse osmosis equipment. Money may also pose challenges because some equipment are expensive. (iii) Lack of environmental concern and awareness This is a common barrier since most people do not have sufficient information about the need to preserve the envirinnment. Awareness on the need to preserve water resources and natural resources, such as trees, should be used in the most economical ways to avoid waste. Trees play a crucial role in purifying the envirionment. Question 4 Treatment methods for reuse or by-product recovery for (a) Dairy (milk) waste containing whey (protein) material Whey is one of the derivatives of a dairy industry. Its properties allows it to be separated through the process of cross flow ultrafiltration (CFUF). CFUF allows the dairy waste to flow at a high speed and pressure through the CFUF membrane. This prevents the accumulation of whey solid matter, thus blocking the membrane. The protein constituents are concentrated, and can be collected. (b) Cutting oil waste out of metal cutting machines The oil used in the cutting machinery can be brought back into use through ultra filtration. High molecular weight particles of metal cuttings are removed. Ultra filtration is a cross-flow separation process, just like reverse osmosis. The process allows for concentration of small pieces of the metal cuttings, thus allowing them to be collect through additional processes such as magnetism. (c) Dye waste from cloth dyeing industry The dye waste from cloth in the dyeing industry consists of many components such as water, and a composition of many colors. Therefore, the dyes can be separated through the process of ultrafiltration. Dye colours are obtained through the many solid substances initially added to it. Through ultrafiltration, the solid molecules that constitue the dye colour are eliminated from dye waste. Question 5 Filter A filter is a mechanical component used for separating solids and fluids. In this process, the mixture from the sedmentation basin is separated into solids and liquid. The liquid in let to proceed to the activated carbon filter, whereas the solid components remain in the filter for further action. Activated Carbon Filters The activated carbon filters for this process are situated between the filters and the final discharge of waste water into the river. They play the role of water treatment by removing the free organic compound or chlorine in the water. This is meant to remove compounds which would otherwise make the water unsuitable for discharge. Filter press From the thickener, the mixture consists of liquid-solid slurry or suspension. This suspension is more like a milk shake because it contains solids in it that easily dissolve in the liquid, and thus carried along with it. However, with the use of the filter press, the solids that are in the suspension are separated from the liquid in order to form polymers, whereas the liquids are moved to the equalizer tank. Equalization Tank The role of an equalizer tank is to provide temporary storage for collected liquids, such as waste water from some streams within the process or microfiltration process. The equalizer tank is used along with the transfer pump. The tank ensures proper holding capacity. The tank helps in equalizing the flow, and can also be used as a staging area to allow for addition of chemicals, activated sludge or any other agents to be added to the waste-water treatment processes. Question 6 (a) Environmental problems of using incinerators and how they can be overcome I. Incinerators produce two forms of ash. The fly ash from the stack has components that make it dangerous, whereas the bottom ash that is mixed with the slag may also be dangerous. The toxics and heavy metals contained in the incinerators’ waste gases are harmful to the environment. However, the toxic substance can be trapped at some levels through the use of expensive technologies instead of getting trapped in the ash. II. Some pollutants can still reside as trapped components in the ash or filters. This calls for the use of special landfills in order to dispose the wastes. (b) Charges for Disposal of Waste with and without Recycling at the Transfer Station Total waste generated Recyclable waste Total cost of disposal with recycling at the transfer station Value of recyclable goods Cost of Recycling waste at the station Transportation Tipping cost Total cost of disposal with recycling Total cost of Disposal without Recycling Transportation Tipping cost Total cost of disposal without recycling Thus, the cost of disposal without recycling is more than the cost of disposal with recycling by a difference of $680. Therefore, it is wise to recycle the waste before disposal in order to make it cheap. Question 7 Estimation of moisture content Mass and volume of the moisture in: Food waste: Mass = 70% x 20 = 14 Volume = mass/density = 14/ 290 =0.0483 m3 Paper: Mass = 8% x 50 = 4 Volume = mass/density = 4/85 =0.0471 m3 Garden trimmings: Mass = 60% x 15 = 9 Volume = mass/density = 9/110 =0.082 m3 Wood: Mass = 20% x 5 = 1 Volume = mass/density = 1/250 =0.004 m3 Metal cans: Mass = 2% x 10 = 0.2 Volume = mass/density Total mass of the moisture content Total volume of the moisture content = 0.1836 m3 Thus, the total volume of the moisture content = 0.1836 m3 Total percentage by mass Percentage of solid waste by mass Mass and volume of the solid waste in: Food waste: m3 Paper: m3 Garden trimmings: m3 Wood: m3 Metal cans: m3 Total volume of the solid waste Total percentage mass of solid waste Thus, density = mass/ volume Kg/m3 Question 8 Seawater desalination process and the functions of the desalination plant in Australia. Seawater desalination refers to the process of converting seawater into the form of potable water. The process of reverse osmosis through the use of some thin-film membranes is used, and has lowered the cost of desalination. In the technology process of reverse osmosis, the water is forced against the semi-permeable membrane under high pressure and in a continuous flow. The main function of desalination process in a desalination plant is to separate water from the many sea water salts. The Sydney’s drinking water treatment plant is more elaborate than just the use of reserve osmosis technology. The plant is meant for packaging drinking water. The output is very high and involves the use of high pressure pumps, storage tanks, and automated bottle filling machines. Unlike desalination plants, Sydney’s drinking water plants involve steps such as purification filling, rinsing, capping, adding of coagulation chemicals, sterilization of water by use of oxidants, filtration processes, further purifications, and water softening. References Jacqueline, V 2009, Waste Management, ABC-CLIO Inc, California. Nicholas, PC 2003, Handbook of Solid Waste Management and Waste Minimization Technologies, Elsevier Science, Burlington, USA. Read More