# Treatment and Effective Utilization of Greywater:
## 1 Introduction  
The United Nations highlighted the SDGs (sustainable development goals) for 2030, where the sixth objective is to represent clean water and wastewater treatment [1]. In developing countries, thousands of deaths were reported due to waterborne diseases, and these results indicate the massive failure to reach the sixth objective of SDGs. With various types of technologies, several decentralized wastewater treatment plants have been installed in developing countries [2].  
Few researchers [3, 4] have referred to developing nations' current opinions about decentralized wastewater treatment systems for big/megacities' sanitation systems as effective and robust. On the other hand, [PERSON] et al. [5] conducted a comparison study of three different wastewater treatment plants (i.e., hybrid, centralized, and decentralized) to understand the issues with the economic perspectives of urban growth. The outcome of the mentioned research is the possible advantages in terms of total discounted lifetime costs. In the second opinion, a decentralized treatment will be more advantageous for lower population growth than expected and lower idleness of the treatment plant. Moreover, centralized treatment plants need a more complicated treatment system to achieve the same quality of treated wastewater with a significant amount of carbon dioxide and energy consumption [6].  
The decentralized solution is now highly adopted because of low environmental impact association rather than the construction of sewer networks to connect the usersto centralized plants [7]. Nowadays, decentralized wastewater management is prevalent and demanding due to economic, social, and environmental advantages [7]. According to WWAP [8], decentralized treatment systems could be another suitable way to the academic/university campus, rural area, or even in some peri-urban regions, where it's challenging to install traditional treatment plants. Simultaneously, greywater could be treated near the sources where it is coming from, and the treated water could be reused/distributed close to or at the same site of the treating unit.  
The small household technique to treat wastewater can be used as decentralized treatment systems. The treatment unit's important highlight is low capital and less operational expenditure occupying small areas other than traditional wastewater treatment unit/plants. The present form of treatment plant has few qualities (i.e., simple operations and annexation of natural gravity-based technologies to reuse the wastewater in situ) to show the low-cost method's main advantages with unique household techniques over traditional plants [9]. In higher pollution, water scarcity, and unsustainable development practices, the demand for treated water will increase in cities/society and academic campuses [1]. Many water demands (i.e., gardening, car washing, floor cleaning, etc.) by institutions and university campuses can be achieved by low-cost treatment units [10; 11; 12].  
Therefore, to reduce the water demand for future sustainability, a simple operation and low-cost method with a unique household technique was introduced to reuse the greywater from the university campus's administrative block. The present work aims to reduce the demand for water or groundwater extraction subsequently. A small unit for greywater treatment is installed in Karunya Institute of Technology and Sciences, an academic campus to manage the administrative block's greywater. The main objective is to develop a low-cost and effective method to treat greywater using gravity-governed filtration techniques.