The world is letting wastewater go waste. That has emerged from a new report titled ‘The United Nations World Water Development Report 2017’. As untreated sewage, agricultural runoff and inadequately treated wastewater from industry continue to deplete the quality of water around the world, we should start looking at wastewater not as a problem but as a part of the solution.
Wastewater is gaining momentum as a “reliable alternative source of water, shifting the paradigm of wastewater management from ‘treatment and disposal’ to ‘reuse, recycle and resource recovery’”.
According to the report, high-income countries treat about 70 per cent of municipal and industrial wastewater they generate. That percentage drops to 38 in upper-middle-income countries and to 28 in lower-middle-income countries.
In low-income countries, only 8 per cent of wastewater undergoes treatment of any kind.
The report claims that failure to address wastewater as a social and environmental problem would nullify other efforts towards achieving the 2030 Agenda for Sustainable Development.
Wastewater as a resource
Wastewater can be a cost-efficient and sustainable source of energy, nutrients and other useful by-products like organic and organic-mineral fertiliser. The benefits of extracting such resources from wastewater go beyond human and environmental health. They have implications on food and energy security as well as climate change mitigation.
However, according to the report, wastewater’s potential as a source of resources remains underexploited. Prospect of energy generation, especially biogas, is largely ignored.
Technologies, which can be integrated in wastewater treatment plants for on-site energy recovery through sludge/bio-solids treatment processes, are available. Sludge incineration in centralised plants through thermal treatment processes is one of the ways to ensure off-site energy recovery.
Moreover, technologies are being developed for recovering nitrogen and phosphorus from sewage or sewage sludge. Phosphorus recovery from on-site treatment facilities like septic tanks and latrines can be feasible by transforming septage into organic or organic-mineral fertiliser.
There’s a possibility of urine collection and use becoming an important component of ecological wastewater management as it contains 88 per cent of nitrogen and 66 per cent of phosphorus found in human waste—essential components for plant growth.
The health connection
Emphasising how managing human waste is beneficial for public health and environment, the report claims that for every US$1 spent on sanitation, the estimated return to society is $5.5.
Given that improved sanitation services can contribute towards reduction of health risks, the report says that health gains may be realised through improved wastewater treatment. However, improved sanitation coverage cannot be equated with improved wastewater management.
Only 26 per cent of urban and 34 per cent of rural sanitation and wastewater services effectively prevent human contact with excreta, and therefore, can be considered safely managed.
The extremely low level of wastewater treatment in low-income and lower-middle-income countries reveals an urgent need for implementing low-cost solutions and safe water reuse options.
To involve citizens in deciding types of sanitation facilities desirable, the report calls for reaching out to marginalised groups, ethnic minorities and people living in extreme poverty in remote rural areas or informal urban settlements. It also calls for engaging with women who bear the brunt of health consequences stemming from unsafe management of human waste.
Management of wastewater
Wastewater is roughly composed of 99 per cent water and one per cent suspended, colloidal and dissolved solids.
To prevent pollution at source, local authorities can prohibit or control the use of certain contaminants. It will eliminate or limit their entry into wastewater streams through regulatory and technical means.
Stating that large-scale centralised wastewater treatment systems are no longer the most viable option for urban water management, the report called for decentralised wastewater treatment systems that serve small groups of people or properties. Such a system allows recovery of nutrients and energy and ensures access to water in times of scarcity.
According to estimates, investment costs for these treatment facilities are only 20–50 per cent of conventional treatment plants.
Region-wise scenario
In Africa, the main challenge related to wastewater treatment is the lack of infrastructure for collection and treatment, resulting in pollution of surface and groundwater resources that are already limited.
In several Arab states, use of safely treated wastewater has become a means of increasing water and it is a main component of water resources management plans. In 2013, about 71 per cent of the wastewater collected in Arab States was safely treated, out of which 21 per cent was used for irrigation and groundwater recharge.
In Asia and the Pacific region, the municipalities and local governments often lack human and financial resources necessary to enforce environmental regulations. As a result, maintenance of water treatment infrastructure and services is a problem. In India, 78 per cent of sewage remains untreated. The report recommends more support to municipal and local governments in managing urban wastewater and capturing its resource benefits.
European and North American region has a relatively higher (95 per cent) access to wastewater treatment. Although tertiary treatment has increased, significant volume of wastewater still gets collected and discharged without treatment, especially in Eastern Europe.
The coverage of urban wastewater treatment in Latin America and the Caribbean has nearly doubled since late 1990s. The coverage is estimated to have reached between 20 and 30 per cent of the wastewater collected in urban sewerage systems.