Introduction

Water is the most essential substance on Earth. Water is essential for all living things, including animals and plants. Without water, there wouldn't be any life on Earth. It is essential for all forms of life and covers 71% of the Earth's total surface. Only 2.5% of Earth's water supply is freshwater. Rapid urbanization and industrialization release huge amounts of wastewater that is used increasingly as an irrigation resource in urban and rural agriculture. It is a major driver of economic activity and supports many livelihoods, especially those of poor farmers. It is being impacted by industrialization and urbanization. The risk of water contamination and the associated sanitation problems is growing in many developing nations. The growing problem of water shortage has a significant impact on economic development, human livelihoods, and the environment. It is therefore essential that the environment today protects water and develops cost-effective solutions to its protection. Globally, there are approximately 1.1 billion people who drink unclean water. According to the World Bank, 21% of all communicable diseases in India are water-related. In 2004, diarrhea was the most fatal disease among Indians, killing more than 535,000 people. In wastewater treatment systems, the major microbial populations are bacteria, protozoa, and viruses. Most of these organisms can cause disease spread. Nitrogen and phosphorus are the two main chemical contaminants found in wastewater. Many chemical pollutants can cause eutrophication, including heavy metals and pesticides. However, the main limiting nutrients are nitrogen and phosphorus. Although many traditional methods of treating wastewater have been around since antiquity, they are expensive and inefficient. To overcome these traditional methods, advanced green technical methods have been developed. This study is about new green technical methods that are showing superior results to the traditional methods. The potential low-cost wastewater treatment using the microalgae method is one of the most promising. Microalgae are responsible for the development of new wastewater treatment methods. They are efficient at reducing toxic components. The quality and availability of water resources are being impacted by rapid population growth and human development. This is most evident at the interface of water and human health, where infectious water-borne diseases continue to be the leading cause of death and morbidity worldwide.

While some techniques are for the reduction of heavy metals, others deal with the reduction of nitrogen or phosphorus. The conventional methods are ineffective at reducing toxic heavy metals, nitrogen and phosphorous, as well as other pollutants.

There is no single method that can treat all compounds in one step. This paper will discuss technological advances in wastewater treatment and sewage water treatment.

2. 2. Background information

The first methods of wastewater treatment emerged from the need to address the negative effects of wastewater discharge on the environment and public health. As cities grew, there was less land available for wastewater treatment and disposal. This was mainly due to intermittent filtration and irrigation. As people grew, so did the amount of wastewater generated. The deteriorating quality of this large volume of wastewater far exceeded the self-purification capacities of streams and rivers.

Other methods were therefore developed to speed up the forces of nature in controlled conditions at smaller treatment facilities. While cleanup is essential to avoid any further release of contaminated wastes to the environment, an industry-friendly technology must be developed. The traditional methods for wastewater remediation include flocculation and activated charcoal, filtration, flocculation, and ion-exchange resins. From the early 1900s to the 1970s, the main treatment goals were: (i) removal of suspended and floating material from wastewater, (ii), treatment of biodegradable organs (BOD), and (iii). Elimination of disease-causing pathogenic microorganisms. From the 1970s through to the 1990s, wastewater treatment was primarily concerned with aesthetic and environmental issues. However, the earlier tasks of reducing and removing BOD suspended solids, and pathogenic micro-organisms were still being performed, though at higher levels. In some streams and lakes, it was also possible to remove nutrients like nitrogen and phosphorus.

Global initiatives were undertaken to increase the effectiveness and distribution of wastewater treatment to improve the quality of surface water. This was possible due to: (i) better understanding of the environmental impacts of wastewater discharges; and (ii) better knowledge of the long-term adverse effects of wastewater discharges. 

Because of the increased scientific knowledge and a wider information base, wastewater treatment now focuses on health concerns related to potentially harmful chemicals that are released into the environment. While the water quality improvement objectives have been maintained, the emphasis has shifted to the removal and definition of toxic and trace chemicals that could potentially cause adverse environmental effects and long-term health effects. 

While the original treatment goals are still valid today, the amount of treatment required has significantly increased. In addition, new treatment goals and objectives have been developed. The typical Dewats system includes primary and secondary treatment, as well as disposal (or use) of solids or treated water. Septic tanks can be used to remove settleable solids and provide anaerobic treatment. This is useful in areas with poor soil or high groundwater. The above modifications enable aerobic treatment to the affluent and prevent floating solids from entering the secondary treatment. They are inexpensive and easy to maintain, but they can fail easily and may leave behind a pathogen-rich wastewater stream. Sand filters are an effective way to remove pathogens from areas with very permeable soils. 

However, they may not be able to work in other locations with more permeable soil types. The use of biological systems to remove radionuclides as well as heavy metals from solutions has received a lot of attention. Massoud and colleagues. A comprehensive review of existing treatment methods was done by Parkinson and Tayler. All biological-treatment methods take advantage of the microorganisms' ability to use diverse wastewater constituents as energy. The metabolic activity can remove contaminants as diverse as raw materials or by-products. The removal method chosen will depend on the number of toxic metals remaining in wastewater treatment facilities. There are many options for final treatment. These include adsorption using activated charcoal or other suitable sorbents, reverse osmosis, and electrochemical treatment.