WSP is the technology with the lowest LCC which would need the highest area of the 11 technologies. WSP is suitable for rural areas or where land is available at a plausible and low cost. WSP is the most affordable because it uses little power and also has low capital, operation, and maintenance costs. In comparison to other technologies, its effluent quality or degree of treatment is average. It necessitates a lengthy treatment period (retention). In this method, sludge removal is a laborious task. This technique's treated wastewater cannot be reused directly. WSP's net savings are positive when compared to the base case SBR.
PHYTORID is the WWTT with the second lowest LCC. It is a natural treatment method that requires little energy and has a low operating cost. Phytorid has a lower O&M cost than WSP. Furthermore, the quality of post-treatment liquid waste is above average in terms of BOD, COD, and coliform removal percentages. The capital cost required to install the Phytorid processing facility is the reason for its LCC being higher than WSP. It can endure load fluctuations and does not entail mechanical device for treatment.
UASB is a technology that requires a little extra amount of space than Phytorid. However, UASB has a limitation in that it cannot meet discharge standards on its own; the effluent must be treated further before discharge or reuse. It cannot remove faecal coliform from wastewater. UASB produces biogas, which is a valuable source of revenue. UASB does not require a mechanical aeration device, which reduces energy consumption and ensures that its performance is unaffected by power fluctuations.
SBT is the next innovation in aspects of LCC values. SBT is a natural treatment method that employs very little energy because no mechanical devices are used in the treatment. Because of its highest capital cost, SBTs LCC is more expensive than the other three technologies. The highest capital cost is caused by the culture and membrane used for lining the bed, as well as the required land area, which is the second highest in all technologies (after WSP). However, its operating and maintenance costs are the lowest of any technology. Its effluent quality is also the best among the technologies, with the exception that coliform removal is not achieved, which is its only disadvantage. However, it can still be used for horticulture and farming purposes.
BioFOR is ranked fourth out of 11 WWTTs. BioFOR is a small treatment system that requires little space and has a low initial investment. However, the O & M cost is higher due to the continuous chemical and power requirements, despite the fact that it requires less manpower for supervision. Its treatment efficiency is above average in terms of TSS, COD, and Coliform removal, but average in terms of BOD removal, hence it is ranked higher (greater number) than other technologies.
TF is an ancient method that is still widely used due to its affordability. Its LCC is higher than WSP and UASB, but its O&M costs is lower in comparison. Power usage is also low compared to other technologies. Its overall degree of treatment is average, which is better than UASB and WSP, but it fails to remove coliform from wastewater. The trickling filter's productivity increases as its rate slows. Due to the spraying mechanism required for its operation as well as the slime layer, the capital cost of TF is the second highest among 11 technologies.
Because of the high power required for the treatment, SAFF has a higher LCC. Due to the specialised media used for treatment, the operating and maintenance costs are also higher than in the previous six technologies. Its capital cost is not significantly affected because it requires significantly less land area. Because of the proprietary media used, the quality of treated wastewater is above average, ranking fourth out of eleven.
The ASP LCC is ranked eighth. It is the most widely used technology due to its high level of treatment and popularity. ASP, on the other hand, necessitates a larger land area than SBR, SAFF, MBR, BioFOR, and MBBR. The reason its LCC being high is its capital cost, O & M cost. During the winter season, it may experience operational issues and is affected by power fluctuations. Its treatment efficiency in terms of percentage removal of BOD and faecal coliform is above average.
SBR is a space-saving technology that provides the highest treatment efficiency. Its LCC is high due to high capital and O&M costs. High costs are incurred as a result of the decanting mechanism and automated system. Because of the control systems, it requires less manpower, though the manpower required must also be skilled, and there is a lower chemical requirement. Because it is the most widely used technology in India, it was chosen as the base case for calculating net savings.
MBBR has a very high LCC due to its high capital, operating, and maintenance costs. Such high costs are seen as a result of the specialised membrane used for treatment, which provides the highest percentage removal.
MBR is the technology with the highest LCC due to its high annual O & M costs. While its land area requirement is the second lowest among 11 technologies, its operating and maintenance costs are the highest. Its treatment level is above average in terms of TSS and BOD removal. However, it is less effective at removing coliforms. It is expensive due to the specialised attention and care required for the membrane (like cleaning to prevent clogging). Costs are also affected by automation and the availability of membranes. Pumping is required to transport the effluent from the reactor unit.
The figure depicting the uncertainty of land cost shows how each WWTTs LCC is affected. The cost of the land was set at a range of 0 to 100 crore Rs. And the LCCs were plotted on two y axes. The primary axis (on the left) is for high LCCs of MBR, MBBR, SBR, and ASP, and the secondary axis (on the right y axis) is for TF, BioFOR, SBT, SAFF, UASB, Phytorid, and WSP.
The graph in Fig. 5 depicts the variation of the discount rate from 0–10% in LCCs of WWTTs. LCC is plotted on the primary and secondary y axes, and the discount rate is plotted on the x axis in this graph. Figure shows the trendline equation in terms of x and y for each treatment technology. The trendline equation represents the change in LCC with respect to change in discount rate. The trendline equation is in same colour code as of the line representing the values. The primary y axis (left) represents MBR, MBBR, SBR, ASP, BioFOR and SAFF while the secondary y axis (right) represents TF, SBT, UASB, Phytorid, and WSP. A combination of two axes is used to clearly observe the changes.
Except for MBBR and MBR, the NS of all technologies is positive, indicating that the other 8 technologies are relatively cheap than SBR. SBT has the highest NS, followed by Phytorid, TF, WSP, UASB, SAFF, BioFOR and ASP. As a result, green technologies are a viable option that should be prioritised. The SIR evaluated is ranked based on its values, with higher SIR receiving higher rankings. WSP, SAFF, ASP, UASB, Phytorid, BioFOR, TF, MBR and SBT are the cost-effective technologies that save more money than SBR, according to SIR. Because its value is less than zero, the SIR of MBBR is not cost effective in comparison to SBR. ASP has high SIR because of its low investment cost difference than SBR. The lower the denominator, the higher is the ratio. The SIR rank indicates which technology will save the most money if preferred over SBR.