Question 1
The solids sources present in the wastewater treatment plant can be established by considering the Type of plant in use. Sludge and solids can be traced in the various systems including grit removal, preaeration, screening, primary and secondary sedimentation, sludge-processing facilities, and biological treatment (Bahadori, 2014). In the process of using biological treatment mechanisms, suspended solid solids are often generated by means of Biochemical Oxygen Demand (BOD), which is a biological conversion technique. To concentrate the streams of waste sludge, thickening criteria may be utilized.
Moreover, in wastewater are iron, copper, aluminum, and other metal ions, which corrodes used equipment. During the oxidation process, these ions would combine with oxygen; thus, producing compounds, which in turn deteriorates the efficiency of machines in use ( Yu, Han, & He, 2017) . Other things of noteworthy entail salts present in water intake, chemicals that are utilized in the treatment process, and those used in processing. Also, the discharge of alkaline wastes may form insoluble hydroxide floc, which would then raise the wastewater pH.
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According to Bahadori (2014), there are also significant concentrations of sulfides, emulsifying agents, and phenols. In the final analysis, any material that is discharged to any drainage system or the oily sewer system should be assessed while considering the target for disposal and treatment of waste.
Question Two
The features of sludge and solids vary depending on specific factors: Solid origin, the aging amount that has occurred, and the processing procedure used. According to Bahadori (2014), grits are composed of denser inorganic solids; thus, this would aid the settling processing with moderately high velocity. Grits may contain in it some organic matter such as grease and fats dependent on the condition of operation. Also, Bahadori (2014) denotes that scum has floatable materials that are glided off the surface of secondary and primary tanks. It may have vegetables, animals, grease, cigarette, plastics, hair paper, skins of fruits, and other organic materials. Note that sludge emanating from the primary settling tank is often gray in color and may dispatch an offensive odor. Another point to note is that the activated sludge will always digest voluntarily alone or when it is intermixed with primary sludge. Also, under favorable conditions, the primary sludge can get digested readily without much input.
The sludge originating from chemical precipitation having signs of metal salts typically contain dark color. In some cases, its surface may be red in color in case it has signs of iron. The lime sludge is often grayish brown in color. Even though the odor that originates from the chemical sludge may be offensive it is not as bad as that one emanating from the primary sludge. The hydrate of either aluminum or iron present in the chemical sludge makes it look gelatinous.
Question Three
The traditional conventional and acceptable technique is to basically some commercial polymers for the role of increasing the generation of sludge in the suspension created, a process called sludge conditioning, then next step is to filter the sludge or press it to eliminate water to form a solid cake. By the time sludge cake is adequately dry, it becomes ready for the final disposal classification by a means of analytical tests to meet the required standards as required by relevant measures as stipulated in the Resource Conservation and Recovery Act.
According to Bahadori (2014), to improve the dewatering features of the sludge, it should be properly conditioned. It is economical to use conditioning methods such as heat treatment, solvent extraction, or even irradiation. Therefore, technical assessment should be made alongside financial situations. Note that the heat treatment technique can be useful when dealing with biological sludge because they often present stabilization or conditioning challenge when other criteria are used (Bahadori, 2014).
It has been realized that the use of filter cake that may need solids greater than 35% are cost-effective in case they are processed via a filter press. Therefore, in designing, the filter plates are supposed to be lined up on a frame, which is suspended and then it is tightly pressed using air pressure. Afterward, the liquid is forced via the filter plate structure with hydraulic pimps, and then the supernatant is sent to the holding tank or final treatment. In the holding tank, additional sludge conditioning, as well as re-filtering, occurs.
Question 4
There are many options available for dewatering. It includes presses such as filter, screw, belt, and rotary, and centrifuges. The most common of all used for forming cake during processing include three belt presser and filter sludge presser. According to Bahadori (2014), belt filter presses has merits such as low energy needed, low setting up capital, low operating cost, easier to maintain and not complex in structure, and it has high-pressure machines capable of generating dry cake. On the other hand, recessed filter presses have advantages such as a high concentration of solid cakes, and has a low level of suspended solids in its filtrate.
When it comes to demerits, the belt filter press is sensitive to the characteristic of the sludge feed which is incoming, limited in throughput as far as hydraulics is concerned, its media life is short, and it needs the sludge grinder in its feed stream. Contrariwise, plate filter pressers have a batch operation, labor cost is high, the cost of equipment is high, and it needs some kind of special requirement in its structure.
The demerit of one technique used over the other depends on external factors, especially on the rate of required dryness of the sludge for low-cost disposal. It would reduce the probability of charges of free liquid stabilization, which occurs at the landfill. Disadvantages include too much time taken in processing sludge into the cake, and it takes long operational hours in clearing sludge cake off the press.
References
Bahadori, A. (2014). Waste Management in the Chemical and Petroleum Industries . West Sussex, United Kingdom: Wiley.
Yu, L., Han, M., & He, F. (2017). A Review of Treating Oily Wastewater. Arabian Journal of Chemistry , 10 , S1913-S1922.
