Reuse Water between Businesses

Reusing products (e.g. water) within different industries is often called industrial symbiosis. Industrial symbiosis is part of a new field called industrial ecology. Industrial ecology is principally concerned with the flow of materials and energy through systems at different scales, from products to factories and up to national and global levels. The keys to industrial symbiosis are collaboration (matching needs and openness) and the synergistic possibilities offered by geographic proximity. The three major opportunities for industrial symbiosis are:

• Exchanging by-products,
• Sharing management of utilities, and
• Sharing ancillary services.

This factsheet will cover opportunities in by-product reuse to optimise water use. Typical examples are the symbiosis of an industry producing heat and nitrogen rich wastewater with fish aquaculture or plant aquaculture.

 

Industry is the fourth largest consumer of water in the world (UNESCO 2009). Industry withdraws 5-10% of global water, ranging from 50% of national withdrawals for developed countries to 5% for developing nations (UNESCO 2009). The primary industrial uses of water are for energy (hydropower), cooling water (from power generation), process water (chemical processes, steam for direct drive power), products and waste disposal (washing) (WBCSD 2009). Industrial symbiosis has the potential to create closed loop processes that drastically alter the industrial process paradigm from extraction to renewal.

Industrial symbiosis can result in considerable environmental and economic benefits for participants, however recent studies in Yale's Journal of Industrial Ecology have found that the majority of benefits occur upstream and not at the plants themselves. Paper and pulp mills operating as industrial ‘symbionts’ had modest improvements in environmental impacts of 5-20% (SOKKA et al. 2010).                  

By-product reuse requires information sharing between firms about what each has to offer in order for firms to self organise. Firms also need assurance about the quality and consistency of the by-product. Biogas settlers may benefit from nutrient rich wastewater from another firm, while a plant or fish aquaculture might need to be promised that the water never contains certain toxins or organisms. By-product sharing must answer to the same concerns as traditional purchasing relationships: supply security, quality control and availability.

Examples of By-Products and their Reuse Opportunities

• Fly ash from power plants for concrete manufacturing
• Organic waste from fermentation, brewery or pharmaceuticals for fertiliser manufacturing (see also use of compost)
• Steam from power plants can be reused by oil refineries
• Treated greywater and other wastewater can be reused in cooling towers for power plant

Examples of Water Reuse Opportunities

With appropriate controls, industrial water can be reused for many industrial processes, including the following:

• Material washing
• Process rinse water
• Crate and pallet washing
• Hardstand and vehicle washing
• Industrial fire protection
• In production line
• pH adjustment

Non-Industrial Water Reuse Opportunities

With appropriate controls, and where risks can be managed to an acceptable level, industrial water may potentially be reused for the following uses:

• Crop and landscape irrigation, including irrigation of municipal parks and gardens (e.g. surface and subsurface drip irrigation)
• Construction (for example, road compaction)
• Dust suppression
• Fire protection
• Toilet flushing at non-residential facilities
• Heating/cooling (air-conditioning) systems
• Commercial car washing facilities or depots
• Commercial laundries or washing machines at non-residential facilities.

Wastewater Treatment Can Increase Reuse

To increase opportunities for reuse between firms treatment systems may be necessary. Collective management of wastewater treatment plants can lower costs for all participants.

Possible Treatments

Possible treatment options for water reuse include: waste stabilisation ponds, aerated ponds, trickling filters, vertical flow constructed wetland, hybrid constructed wetland, freesurface constructed wetland and horizontal flow constructed wetland.

Treatment options where biogas can be produced using anaerobic digestion: UASB reactors, biogas settlers or in large scale digesters.

Advanced (more high-tech options): activated sludge, MBRs, advanced oxidation processes, ozonation, activated carbon.

Another form of industrial symbiosis can be simple utility sharing. For example, several firms could share a closed-loop solvent recovery programme collectively run or in cooperation with a local wastewater treatment service. Each firm may not use enough solvents to justify a system of solvent recovery, but several firms together can. Pulling solvents out of the waste stream reduces the wastewater treatment necessary and creates the potential for reuse (ASHTON 2008).

Geographically close firms can save money and energy by sharing ancillary services like transportation, landscaping, waste collection, and emergency management. For example, companies could share reservoirs for storing water for industrial fire protection (ASHTON 2008). Examples:

• The term industrial symbiosis was popularised in the small town of Kalundborg, Denmark to describe their unique partnership for sharing groundwater, surface water, wastewater, steam, sludge, gas, sulphur, fuel, etc. between several different industries.

Another example of industrial symbiosis is located in Switzerland. The Wolhusen Tropenhaus represents long-term cooperation between private and public enterprise. Waste heat from a nearby natural gas plant is run through a steam generator to produce energy for the greenhouse nearby. The waste heat from that process is used to heat a nearby hospital and to heat water for the greenhouse's aquaculture system. Currently the hospital and greenhouse use 40% of the natural gas plants waste heat.

Primarily, case studies of industrial symbiosis have come from regions with large-scale heavy industrial processes like Kwinana industrial area in Australia or Rotterdam harbour in the Netherlands (ASHTON 2008). However, small-scale agricultural businesses have also engaged in industrial symbiosis, like Montfort Boys Town in Fiji (ASHTON 2008). Many also exist that are not documented or advertised as such.