Enhancing zero discharge for sustainability by waste water recycling

A waste water recycling plant in southern California, USA

A waste water recycling plant in southern California, USA

 Fungai Khuzwayo
FRESH water, that precious liquid which is often equated to life itself, is running out owing to climate change and other factors.

An unfortunate development facing the world today is its supply of fresh water is finite and threatened by pollution.  Rising demands for water to supply agriculture, industry and cities are leading to competition over the limited fresh precious liquid.

Water conservation and recycling produce substantial environmental benefits, arising from reductions in water diversions and the impacts of waste water discharges on environmental water quality.  However, substantial water quality tests are required to guarantee the safety of public health.

The concept of reclaimed waste water to be considered as a resource for indirectly augmenting the potable supplies has been a subject of debate. Wastewaters can introduce microbial and chemical contaminants into the environment.

Even though the existing waste water treatment plants can successfully remove the conventional contaminants such as organics and nutrients, they are less effective in removing the emerging contaminants such as pharmaceutical and personal care products, endocrine disrupting chemicals and new emerging microbial contaminants.

Problems concerning water sanitation stem from the rise in urban migration and the practice of discharging untreated waste water.

The uncontrolled growth in urban areas has made planning and expansion of water and sewage systems very difficult and expensive to carry out.

Industrial development has always been afflicted with the issue of residue disposal, industrial effluents are one of the largest sources of water pollution and one with the most lethal composition of toxins.

As a matter of serious concern one of the ways to reduce the impact of water scarcity and pollution is to expand water and waste water reuse by wastewater recycling.

Water, as one of the world’s most valuable resources, is under constant threat due to climate change, exponential population growth as well as pollution impacts. Industrial and municipal water reclamation and recycling is now one of the most promising efforts to stem the water crisis.

The sewage contamination of our lakes, rivers and domestic water bodies have reached dangerous levels warranting attention by the responsible regulatory bodies and the whole community at large.

There is a growing awareness of the impact of sewage contamination on rivers and lakes resulting in severe eutrophication of the water bodies.

Eutrophication is a syndrome of ecosystem responses to human activities that fertilise water bodies with nitrogen (N) and phosphorous (P) often upsetting both acquatic and terrestrial animals and plant population resulting in the degradation of the water and habitat quality.

Pristine aquatic ecosystems function in approximate steady state in which primary production of new plant biomass is sustained by N and P released as byproducts of microbial and animal metabolism.

This balanced state is disrupted by human activities that artificially enrich water bodies with N and P, resulting in unnaturally high rates of plant production and accumulation of organic matter that can degrade water and habitat quality.

These inputs may come from untreated industrial effluent, sewage discharges, sewage treatment plants, etc.

In some cases the climax stage of algal blooms can release toxic chemicals such as domoic acid to the aquatic environment, creating elevated metabolic risks to a variety of fish and other aquatic mammals.

Water recycling is the reuse of treated waste water for beneficial purposes such as agricultural, landscape and landscape irrigation, industrial processes, toilet flushing, or replenishing groundwater sources also known as groundwater recharge.

Water recycling allows communities to become less dependent on ground water and surface water sources and can decrease the diversion of water from sensitive ecosystems.

It also may reduce the nutrient loads from waste water discharges into waterways, thereby reducing and preventing pollution.

This water source may also be used to replenish overdrawn water sources and rejuvenate or re-establish the ones previously destroyed.

Water reclamation and reuse constitute one of the major trends in water management. The drivers are population growth, urbanisation, industrialisation in emerging markets, pollution of raw water sources and to some extent, climate change.

The consequences derived from these phenomena are water shortages and the excessive use of ground and surface water, which are putting severe pressure on the responsible authorities, municipal and industrial consumers.

Statistics reveal that in a developing urban society, waste water generation usually averages 30 to 70m3 per person per year.

In a city of one million people, the waste water generated would be sufficient to irrigate approximately 1,500 to 3,500 hectares of land.

According to the World Bank, “the greatest challenge in the water and sanitation sector over the next two decades will be the implementation of low cost sewage treatment that will at the same time permit selective reuse of treated effluents for agricultural and industrial purposes”.

Our urban waste water treatment has received less attention compared to water supply and treatment.  The waste water system is a linear treatment system that is based on disposal.

The traditional system needs to be transformed into a sustainable, closed loop urban waste water management system that is based on the conservation of water and nutrient resources.

To achieve an ecological waste water treatment, a “closed loop treatment system” is recommended. Many present day systems use a “disposal –based linear system”.

The traditional linear treatment systems must be transformed into the cyclical treatment to promote the conservation of water and nutrient resources. Using organic waste nutrient cycles, from “point – of- generation” to “point – of – production”, closes the resource loop and provides a better approach for the management of valuable wastewater resources.

Failing to recover organic waste water from urban areas means a huge loss of life- supporting resources that, instead of being used in agriculture for food production, fill rivers with polluted water.

The development of ecological waste water management strategies will contribute to the reduction of pathogens in surface and ground water to improve public health.

In the growing number of conflicts between agricultural and domestic use of scarce water resources, an increased use of treated waste water for irrigation purposes is vital.

A key component in any strategy aimed at increasing the coverage of waste water treatment should be the application of appropriate waste water treatment technologies that are effective, simple to operate, and low cost (in investment especially in operation and maintenance).

Appropriate technology processes are also more environmentally friendly since they consume less energy and thereby have a positive impact on efforts to mitigate the effects of climate change.

Appropriate technology unit processes include; lagoons treatment (Anaerobic, Facultative and Polishing).

In wetlands treatment, natural forces (chemical, physical and solar) act together to purify the waste water, thereby achieving waste water treatment.

A series of shallow ponds act as stabilisation lagoons, while water hyacinth or duckweed act to accumulate heavy metals. Multiple forms of bacteria, plankton, and algae act to further purify the water.

Wetland treatment technology in Zimbabwe offers a comparative advantage over conventional, mechanised treatment systems because the level of self-sufficiency, ecological balance, and economic viability is greater.

The system allows for total resource recovery. Lagoon systems pose a low cost technology where sufficient, non-arable land is available.

Another treatment option where land availability is not a challenge is anaerobic digestion. Anaerobic bacteria degrade organic materials in the absence of oxygen and produce methane and carbon dioxide.

The benefits include; a reduction of bio-solids volume of up to 50 – 80 percent and a final waste sludge that is biologically stable can serve as rich humus for agriculture.

To alleviate water shortages, serious consideration must be given to waste water reclamation and reuse.

There is, however, a need for appropriate risk assessment before implementing the reuse of waste water.

Proper consideration of the health risks and quality restrictions must be a part of the assessment. Source point measures rather than end of pipe solutions are essential.

Source point measures require extensive industrial pre-treatment interventions, monitoring and control programmes, and incentives for the community to not dispose any harmful matter like sanitary pads and pampers into sewers.

For the implementation and promotion of new technology, strategies must include local participation as well as municipal action.

Inclusive business strategies are another avenue that can create buy in by local communities, with examples such as fish farming which makes use of the reclaimed water.

An inclusive business is a sustainable business that benefits low-income communities. It is a business initiative that, keeping its for-profit nature, contributes to poverty reduction through the inclusion of low income communities in its value chain.

Alleviating poverty in these communities will thus serve to create a strong sense of ownership by members of the community from such projects; such pride helps to ensure sustainability of the water supply and sanitation systems.

About the writer: Fungai Khuzwayo is a Technical Projects & Office Administrator with BUMIRA Environmental Consultants/BCSDZ Matabeleland Branch Secretariat. Contact Details: Email: fkhuzwayo@bumira.net. Cell: +263 774 010 436

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