How is sewage treated?

No matter how stringent measures are taken and no matter how advanced technology is adopted, the discharge of sewage is inevitable and since water pollution is already a fait accompli in many places, the study of sewage treatment techniques and methods becomes very necessary. At present, according to the principles and methods of the natural sciences adopted, sewage treatment is generally categorized into physical, chemical, physico-chemical and biological methods.

Physical method is the use of physical action to remove sewage floating, suspended matter and oil, etc., in the treatment process does not change the chemical nature of pollutants, while recovering useful substances from the wastewater in a simple water treatment method. Commonly used in the physical methods of water treatment are gravity separation, filtration, evaporation and crystallization and physical conditioning methods. Gravity separation method refers to the use of sewage sediment, suspended solids and oil in gravity and water separation characteristics, after natural settlement, the specific gravity of the sewage in the suspended matter removed. Centrifugal separation method refers to the centrifugal effect of mechanical high-speed rotation, the different quality of suspended or emulsified oil through different outlets were diverted out for recovery. Filtration method is to use quartz sand, screen mesh, nylon cloth, grill, etc. as filtration media to retain suspended matter. Evaporation and crystallization method is to heat the water in the sewage to gasify, and the solids get concentrated and crystallized. Magnetic separation method is the use of magnetic field force, rapid removal of wastewater difficult to separate the fine suspended solids and colloids, such as oil, heavy metal ions, algae, bacteria, viruses and other pollutants.

Chemical method is to make toxic and harmful wastewater into non-toxic and harmless water or low-toxicity water, a method, mainly acid and alkali neutralization method, coagulation, chemical precipitation, oxidation and reduction. Acid-base neutralization method refers to the use of alkaline substances to deal with acidic wastewater, acidic substances to deal with alkaline wastewater, so that the two neutralized, and then filtered wastewater can be basically purified. Coagulation method refers to the addition of alum to the sewage, stirring thoroughly, so that the colloidal ions with charge precipitation down. Chemical precipitation method is to add chemical precipitant in wastewater, so that it reacts with heavy metal pollutants in wastewater to generate insoluble solids and precipitation. Redox method is to add chemical oxidizing agent or reducing agent, selectively change the nature of toxic substances in wastewater, so that they become non-toxic or slightly toxic substances; electrochemical method is the use of electrolysis tank chemical reaction, treatment of pollutants in wastewater, a technology, including electrolysis oxidation reduction, electrolysis coagulation and other different processes.

Physical-chemical method is the use of physicochemical action to remove pollutants in wastewater, mainly adsorption method, ion exchange method, membrane separation method, extraction method and so on. Adsorption method is to put into the wastewater adsorbent such as activated carbon, the use of its physical adsorption, chemical adsorption, oxidation, catalytic oxidation and reduction and other properties to remove a variety of pollutants in the wastewater method. Ion exchange method is to remove harmful ions in wastewater with the help of ion exchangers in the exchange of ions with the ions in the wastewater. Membrane separation method is the use of special membranes (ion exchange membranes, semi-permeable membranes) selective permeability, the solute in the wastewater or particles of the separation or concentration of the method is collectively referred to. Extraction method is the use of solutes in immiscible solvents in the solubility of different, with a solvent solute from another solvent composed of the solution of the operation method.

Biological methods utilize microorganisms to break down organic pollutants in order to purify wastewater. Wastewater that is discharged without treatment will gradually become clearer and the odor will disappear after flowing for a certain distance; this phenomenon is a natural purification of the water. Microorganisms in the water play the role of cleaning sewage, they take organic pollutants in the water body as their nutritional food, through adsorption, absorption, oxidation, decomposition and other processes, organic matter into simple inorganic matter, both to meet the microbial needs of their own reproduction and life activities, but also to purify the sewage. Microorganisms such as bacteria, algae and protozoa have a strong ability to adsorb, oxidize and decompose organic pollutants. They have different requirements for oxygen in the treatment of waste, according to which the biological method can be divided into two categories: aerobic and anaerobic treatment. Aerobic treatment is aerobic treatment, anaerobic treatment is carried out under anaerobic conditions. Biological method is the longest and most widely used and quite effective method of wastewater, especially for the treatment of organic sewage.

Links: Crossing the Water Divide

The Fifth World Water Forum was held in Istanbul, Turkey, in March 2009, and was attended by 28,000 delegates from 156 countries and territories around the globe, including more than 90 ministers, 63 mayors, and 148 parliamentarians. The theme of the Fifth World Water Forum was "Crossing the Water Divide," with specific sub-themes and topics below.

Subtheme 1: Global Change and Risk Management

Theme 1: Responding to Climate Change

The understanding of the many causes and consequences of global warming is rapidly growing. The main question facing the water community is how will climate change affect the water cycle? What are the key strategies for addressing climate change and reducing human and environmental risks? Given the many different physical and economic conditions and the inherent uncertainties associated with impacts and required actions, it is important to engage in substantive discussions on policy responses, technical options, political resolutions, and top priorities through the Issues Sessions.

Issue 2: Water-related migration, land use and habitat change

Increasing pressures on water, land and habitat lead to population movements, which in turn have an impact on the new habitat. Can the demand for migration and its impacts on settlements be reduced by improving water management, land and the environment? What are the strategies for appropriate water supply development and management to cope with current and future population growth?

Issue 3: Managing disasters

Currently, increasing urbanization and climate change, and the resulting more frequent and extreme disasters, pose new threats to the lives and economic security of hundreds of millions of people. The first priority is to prepare for disasters and to cooperate among government agencies at different levels to build and maintain critical water infrastructure to minimize the loss of lives, jobs, property and business continuity in the event of a disaster. In this context, there are many different perspectives on the urgency of this issue, on the cost-effectiveness of different levels of preparedness, and on the support for official development assistance (ODA) needed by the most vulnerable, least developed countries (LDCs) and small island states.

Sub-theme 2: Promoting human development and the Millennium Development Goals (MDGs)

Issue 4: Water and sanitation for all - guaranteeing adequate facilities to protect public health

There is broad ****ing recognition of the goal of providing water, sanitation and health for all. At the same time, there is less awareness of how to achieve this goal and, more fundamentally, of the basic articulation of achieving a safe water supply and providing environmentally sustainable sanitation. Following the International Year of Sanitation 2008, the Fifth World Water Forum will provide a new opportunity to discuss the real state of progress on water, sanitation and health, and the political commitment needed to tackle the world's most challenging regions. The question of whether local entrepreneurs can fundamentally change the paradigm of water and sanitation provision will be discussed at the Forum, along with the more traditional roles of financing institutions, communities and operating partners.

Issue 5: Water and Energy

The growing shortage and increasing cost of energy resources have important implications for the future of water production, use and treatment, including desalination and water recycling. At the same time, increasingly scarce water resources are needed to meet increasing energy demands. Hydropower requires water to be stored behind dams and water to flow through turbines to generate electricity without consuming natural resources. Water and energy policies need to be harmonized when combined with community-based actions and appropriate technologies. But can this harmonization be achieved in practice?

Issue 6: Water and food to end poverty and hunger

More food needs to be produced from less water and land. Growing populations, the challenges posed by changing diets, and the unquenchable thirst for agricultural biomass energy are placing increasing pressure on finite land, water, and environmental resources, both globally and locally. How do we find the balance to achieve sustainable development? How do we respond to food security and energy security, and how do we need to adjust market access and pricing regimes to prevent the worst impacts on poor people.

Issue 7: Developing and protecting the multiple services of water

Multiple uses of water, conflict or harmonization? By using water more efficiently, and by harmonizing it with agricultural uses, water can better meet household, urban and energy production needs. Significant returns on investment can be achieved when institutions and agencies are ready and able to optimize the multiple uses of water. Is it necessary to institutionalize and scale up multiple uses to better contribute to the achievement of the Millennium Development Goals? What administrative, institutional and financial measures are needed to enhance the sustainability of these services?

Sub-theme 3: Managing and protecting water resources and their supply systems to meet human and environmental needs

Theme 8: Basin management and transboundary water cooperation

With increasing pressures on water resources, coupled with the projected impacts of climate change, improved management, and cooperation in the management of transboundary water resources, is becoming an essential element of meeting the needs of people and the environment.

Issue 9: Securing adequate water resources and storage facilities for agriculture, energy and urban needs

Securing adequate water resources is important for development, and even more so when considering the increasing impacts of climate change. This requires adequate natural and artificial water storage facilities. How can a compromise be found among the many different perspectives on protecting the resource and its ecosystems while adequately meeting human needs in a sustainable manner?

Issue 10: Sustaining natural ecosystems

In order to sustain ecosystems and environmental flows for human well-being, natural ecosystems and environmental flows should be an integral part of the entire process of planning, decision-making and implementation of land and water resources management. What role can existing international laws and agreements play? What needs to be done at the national and local levels of planning to take human needs and local values and conditions into account?

Issue 11: Managing and protecting surface water, groundwater, soil water and rainwater

Rainfall is the largest available source of water, but its management is the least developed. Groundwater is the most reliable source of water, but also the most vulnerable, susceptible to pollution and over-exploitation. Despite this, institutional inertia encourages water management to remain focused on surface water. To protect these different water resources and freshwater ecosystems and to maximize their potential in a responsible manner, an integrated approach to planning and management of surface water, groundwater, soil water and rainwater is advocated. So what changes to the legal and institutional frameworks are needed? How best to inculcate scientific knowledge in politicians?

Sub-theme 4: Water governance and management

Issue 12: Implementing the right to water and sanitation and improving access to water and sanitation

The right to water and sanitation is indeed very relevant, and the recognition of the right to use water and sanitation will inevitably lead to improvements in people's access to water and sanitation, in particular those living in poverty, and in the access of people in situations of conflict. Recognizing the right to water and sanitation will inevitably improve access to water and sanitation, especially for the poor, and in situations of conflict. Will the right to water and sanitation actually make a difference for poor and marginalized people? How can these people use the right to water and sanitation as a tool to access water and sanitation and to hold governments and other actors accountable? If the right to water and sanitation is a tool to drive progress on the Millennium Development Goals, what actions are needed? The right to water is clear, but have we reached the same level of understanding of what the right to sanitation entails? Do we know how to operationalize the right to sanitation?

Issue 13: Regulatory approaches to improving operations

There is a worldwide push to establish regulatory frameworks for independent operators and service providers as a means of clarifying mandates and responsibilities, and improving services and economic operations. But does regulation work in all situations? What is the current situation? What role can regulatory frameworks play in the future with regard to wastewater reuse? What role will it play in the sustainable use of groundwater resources?

Theme 14: Ethics, transparency and stakeholder empowerment

While the concept of "water ethics" may seem indisputable, better water management requires an accepted interpretation of it. Is this possible? At the same time, developing such a standard would encourage stakeholders to participate in decision-making processes. These decision-making processes would be transparent, responsibilities would be clarified, and fair opportunities would be provided. What other measures would accomplish this?

Issue 15: Optimizing public and private roles in water services

Economic and labor conditions are changing, and the roles and responsibilities of public **** and private organizations in the provision of water services are likewise changing. In this context, in addition to outsourcing to the private sector to add special roles, communities are moving to a variety of service delivery models, including collectivization of utilities in the case of public ownership, delegated service delivery models, and hybrid models involving small service providers. In some cases, these changes have become controversial due to concerns about loss of community control as a result of greater private sector involvement.

Issue 16: Institutional arrangements for efficient and effective water resources management

For water resources management to be equitable, efficient and effective, it needs to be coordinated at all levels of government. This theme focuses on the coordination and allocation of water resources in the context of increasing water scarcity, concentrating on some of the issues that are misunderstood and on which there is no agreement, including ways of establishing water governance aimed at coordinating the various water management agencies, all water-related sectors, and stakeholders, both at the national level and at the regional level.

Sub-theme V: Financing

Issue 17: Sustainable Financing for the Water Sector

Achieving the Millennium Development Goals (MDGs) and addressing global challenges requires investment. The capacity to lend is available, but the capacity to borrow is not. What do different stakeholders need to do to increase their borrowing capacity? What do financial institutions need to do to make their financial products meet the needs of borrowers? What can local governments do to become more reliable financing stakeholders so that operators and utility managers can expand investment coverage and improve services? What non-traditional financing mechanisms are feasible for improved watershed management?

Topic 18: Pricing Strategies as a Tool for Water Sector Sustainability

Water pricing strategies respond to policy objectives of financial, social, economic and environmental sustainability, but water pricing on its own is not an appropriate means of achieving social policy objectives. This topic will attempt to reveal the main trade-offs between urban water supply, rural water supply and irrigation services, including pricing strategies for sanitation service provision.

Topic 19: Financing Policies and Strategies to Support the Poor

While adequate financing is necessary to extend services and meet the needs of poor communities, many financing mechanisms do not really serve the poorest. Many specific financing and legal solutions will be investigated to accelerate access to affordable water and sanitation services for the poor.

Sub-theme 6: Education, knowledge and capacity building

Issue 20: Education, knowledge and capacity building strategies

Much money and effort has been invested in capacity building. But how successful is capacity building at different levels? What are the results of capacity building at the business and operational level in particular? How can we ensure that the various stakeholders, including children, young people and educators, contribute and have equal access to the vast and rapidly growing body of knowledge and experience that we have? Scientific knowledge must be relevant to current issues and be available to all in an effective and timely manner so that communities with local knowledge can make a difference in reducing the impacts of major water issues.

Issue 21: Water Science and Technology - Appropriate and Innovative Solutions for the 21st Century

In order to build a better future, water management strategies should draw on a number of ideas from outside the industry. Can the combination of emerging technologies and standard personalized information platforms lead to flexible systems that respond quickly to change?

Topic 22: Utilizing the Resources of Professional Associations and Networks to Achieve the Millennium Development Goals (MDGs) Although professional associations and networks have a very important role to play in the achievement of the MDGs, at present their role remains small. This topic focuses on the question of whether professional associations are seen as an underutilized resource by development agencies, and how they can be used and encouraged to support professional associations and networks so that they can make a significant contribution to the achievement of the MDGs.

Topic 23: Information ****enjoyment

The wealth of open information is not just a question of access to information, but also of understanding which elements are most important and which means can be put into practice to best ****enjoy knowledge. With only 20% of water-related information easily accessible, how well do we already understand the water cycle in terms of science and practice?

Issue 24: Water and Culture Cultural diversity and its integration with water management approaches, science, policy development and capacity building present not only opportunities but also challenges for sustainable water resources management. In addition, history provides important knowledge to help address current and future challenges.

Afterword

In June 2009, the average monthly temperature in Beijing reached 28.8°C, while between 1999 and 2008, the average monthly temperature in June was 24.9°C, meaning that the average monthly temperature in June 2009 was nearly 4°C higher than normal. High temperatures directly lead to record high water consumption. As the temperature continues to rise, the urban water supply also continues to increase. June 1, the urban daily water supply of 2.6 million cubic meters, exceeding the highest daily water supply since 2000, than the highest daily water supply in 2008, 140,000 cubic meters. June 24, the urban daily water supply of 2.66 million cubic meters. June 25, the urban daily water supply amounted to 2.73 million cubic meters. June 29, water supply The highest record was set again, the urban daily water supply reached 2.78 million cubic meters, the highest level in Beijing's 100-year water supply history.

What happens in Beijing when the temperature rises and the water consumption increases steeply? Similar situations are occurring pretty much all over the country and around the globe. Rising temperatures may be the natural ebb and flow of climate change, but we cannot rule out the possibility that human activity is contributing to it. In addition, human activities have caused atmospheric pollution, and the destruction of the ozone layer has led to an increase in the number of accidents in which ultraviolet rays cause harm to human beings and other living creatures; and reports of food failures as a result of acid rain pollution have appeared frequently in the press. The destruction of the ozone layer, warming of the climate, the threat of acid rain and the water crisis are things that are happening around us.

It's time to reflect on human behavior, it's time to consider the way human beings create wealth, it's time to bet on the sunshine, air and water that we can't leave. Only when the sun is still bright, the air is still fresh, and the water is still clear, will mankind have a better tomorrow to look forward to. Contents of the first chapter of air pollution and ozone layer destruction once air pollution leads to the destruction of the ozone layer, resulting in the ozone hole, is equivalent to the sunshine added "toxin". Without the ozone layer's "isolation", sunlight may become synonymous with disaster for the earth, living creatures, and human beings.