Wastewater treatment pilot making green-brewing strides at PE plant
Volume: Vol 2 Issue 4 |  Tuesday, 03 May 2011 |  Eleanor Seggie  |  0 comment

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Rhodes University’s (RU’s) environment-friendly wastewater treatment plant has successfully treated about 0,15% of the water used each year by South African Breweries’ (SAB’s) iBhayi brewery during its pilot phase.

The project, dubbed Project Eden, is a first for the South African brewery industry and was initiated at the Port Elizabeth plant at the end of 2008, with an initial investment of R1-million from the SABMiller Group Technical unit. The wastewater was treated to discharge standards suitable for reuse in irrigation and other second- ary water uses.

RU Department of Ichthyology and Fisheries Science’s Dr Cliff Jones says 75% of the water used in breweries ends up as effluent and its disposal has financial and environmental impli- cations as well as a large energy footprint. It is food-grade water with nutrients in an unavailable, and therefore unusable, form.

The plant is the brainchild of the RU department and recovers water from brewery effluent using high-rate algal ponding (HRAP) built within a greenhouse and a constructed wetland, downstream of the brewery’s anaerobic digestion (AD) effluent treatment plant. Once the effluent has undergone AD, it enters the integrated algal ponding system: a primary facultative pond and the HRAP.

The algae assimilate nutrients from the effluent, which is then transferred by controlled flow to the pilot-scale constructed wetland, where locally sourced typha (cattail) plants further absorb nutrients. At this point, the discharge is no different to that of normal river water. To test its quality, the treated effluent is then transferred back to the greenhouse and used to irrigate hydroponic lettuce, fit for human consumption, and into fish-rearing ponds. At present, at full production, 600 heads of lettuce are produced in six weeks.

Initially, the survival and growth of hardy tilapia fish were tested in the ponds, but high-value ornamental swordtail fish are now being used and are showing healthy growth and reproduction.

Peer-reviewed data from May 2009 to June 2010 shows that, on average, the HRAP decreased the chemical oxygen demand (COD), or the amount of oxygen used from the environment by polluted water, by more than 50%, bringing the treated water close to the Depart- ment of Water Affairs (DWA) general limits. The wetland also reduced the COD, largely within DWA general limits. The amount of nitrogen, a by-product of the brewery process, was also reduced in the system to within DWA general limits. As such, the RU team believes that the system is effective in treating brewery effluent.

RU’s Environmental Biotechnology Research Institute (Ebru) assisted in developing some of the inexpensive and environmentally sustainable technology used in the project.

Jones says the system provides other benefits, including low energy inputs, capital and running costs and maintenance. Further, preliminary results suggest that the treated water can be reclaimed and by-products, such as algae, harvested and reused in other applications.

SAB is reviewing the financial feasibility of having 20% to 30% of its effluent water treated through the system for reuse in the iBhayi brewery and the company is in discussion with the Nelson Mandela Bay Metropole regarding this. SAB is investigating the use of this technology at one of its other breweries although, given the high land use of the constructed wetland, it is not suitable for breweries with space limitations.

Another drawback is that the treated water contains a concentration of chlorides (salts) and is currently only suitable for discharge into saline estuaries, such as that of the Swartkops river, near the brewery. However, with further investment in the plant to reduce the chloride concentrates and the conductivity of the effluent after the constructed wetland, the treated water would meet general discharge standards. SAB follows all the necessary municipal requirements and processes to discharge the treated effluent.

SAB GM of Newlands and iBhayi Breweries Diarmaid De Burca says the brewing process is intrinsically water intensive and, given the country’s water scarcity, its future water security poses a risk to SAB’s business and to the communities in which it operates. The company’s water strategy is driven by its sustainable development priority to “make more beer using less water” and its water efficiency has improved by 8% over the past two years, to an average of 4,1 ℓ of water for every litre of beer produced. It aims for a 13% reduction in the water ratio, from 4,1 to 3,6 by 2015.