Water Quality; Wastewater Management - Essay Example

Water Quality; Wastewater Management Compare and contrast the secondary water treatment methods to the tertiary water treatment (also known as advanced or final water treatment) methods, in the context of the wastewater treatment process. In your answer, consider that there are multiple secondary water treatment methods and multiple tertiary water treatment methods. The secondary wastewater treatment methods are employed after the primary physical treatment operations while the tertiary treatment units follow the secondary treatment.

The tertiary treatment aims in the complete removal of contaminants as well as any pathogenic organisms to enable the treated water for various reuse applications (Malzer et al, 2002). The wastewater having very high amount of dissolved BOD or COD would require either biological treatment processes, like activated sludge treatment, trickling filters upflow anaerobic sludge treatment, or chemical treatment units like coagulation techniques, filtration with ion exchange etc. These methods would not be adequate for complete elimination of the dissolved impurities.

For example in the case of municipal wastewater, the secondary treatment would results in the reduction of organic part of the total contaminants dissolved in it. On the other hand, the pollutants like nitrates and phosphates or bacterial/microbiological contamination would not be totally removed using these methods. Hence, advanced treatment operations are additionally required for the removal of the aforementioned impurities (Malzer, 2002). The treatment processes employed in such situations are classified as the tertiary treatment.

The techniques are usually nitrification and denitrification units which are also biological methods undertaken with the help of bacterial mass. On the other hand, phosphates too need specialized treatment units for its removal. Further, if the objective is to eliminate the bacterial contamination, disinfection systems need to be provided appropriately as the tertiary unit operation. Thus the methods used under the secondary and tertiary treatment units are of multiple types and each having different purpose.

Thus in a typical treatment system where the secondary operations are dependent on the activated sludge plants, the operations consist of a series of inter linked units having a settling basin where the sludge is separated from the treated water, following by sludge thickening, sludge drying and sludge disposal. The treated water from the settling tank marks the end of secondary treatment operations the water would still contain large amount of bacterial contamination along with high levels of nitrates and phosphates (Malzer, 2002).

And hence the clarified water from the settling unit flows into tertiary treatment operations. 2) Discuss the appropriate uses of reclaimed water.The water moving out of a tertiary treatment unit could be used for multiple uses. The important applications are explained as follows ;As part of resource reduction exercises, the treated water could be used for gardening and floor washing where in most of the situation large quantities of potable water are used. Though there is a general practice of using secondary treated water for the gardening and agriculture, the possibility of pathogenic bacteria entering into the fruits and vegetables cannot be ruled out.

Thus its always safe to use the tertiary treated water for the reuse needs. Also, in the industries where stream is to generate for energy requirement, it would be better to use the tertiary treated water rather than potable water.Another area of potential application of reused water is in the toilet flushing operations. The large quantities of water that goes directly into drain could be the recycled water thus helping to save large volumes of water. 3) Explain whether you would recommend secondary treatment or tertiary treatment for the groundwater recharge, if this water were to end up being used for drinking.

If the water need to be used for drinking purpose it must be free from all the pathogenic matter besides removing all the dissolved chemical and organic compounds. A properly functioning tertiary treatment unit would be able to achieve the standards set for the potable water. Besides, the water recharged into the ground if made to infiltrate through the thick sand layer, it would further help to eliminate the dissolved impurities and bacterial mass thus ensuring additional safety. Thus the tertiary treated water if recharged through the ground would be amenable for drinking purpose also.

ReferenceMalzer, H.J., Gimbel, R. and Schippers, J.C. (2002), Innovations in Conventional and Advanced Water Treatment Processes: Selected Proceedings of the International Conference on Innovations in Conventional . science & technology: Water supply, IWA Publishing.