Engineering and project management consultancy Royal HaskoningDHV presented an academic paper that highlights the possibilities of water and feedstock recovery for the food and beverage industry at this year’s Water Institute of Southern Africa conference, held last month in Durban.

In 2011, international food manufacturing company Mars requested assistance from Royal HaskoningDHV to achieve its water goal as part of Mars’ ‘sustainable in a generation’ programme, which aims to see the company limit its environmental impact by 2040.

Subsequently, Royal HaskoningDHV conducted a series of tests and process evaluations, which resulted in a water and glucose recovery rate of 84% in one of its heaviest water-consuming manufacturing processes.

Royal HaskoningDHV water process engineer Marco Kerstholt, a member of the team that worked on the project, tells Engineering News that the consultancy followed its proprietary WaterScan approach to identify potential water-reduction opportunities.

This approach enabled Royal HaskoningDHV to better understand Mars’ production process through the development of mass balances of the water, consumables and energy used in the process, and identification of the key operating parameters for water consumption.

Subsequent to the determination of the mass balances, a number of options were available to Mars to reduce its water consumption.

Most of the options were process-integrated solutions, which would only allow for water savings of up to 30%.

By analysing the effluent stream of the process, which includes water, glucose and particulate matter, it was found that separating the various components of the effluent stream made it possible to reuse the water and glucose inputs of the manufacturing process. The only waste product in the process would, therefore, be the particulate matter.

Kerstholt notes that, thereafter, it was important to identify the correct technologies to separate the particles from the liquid phase, and a technology that would separate the water and glucose liquid fractions.

Filtration technologies were initially con- sidered to separate the particulate matter from the initial liquid phase; however, owing to the significant fraction of the particles and the potential for biological fouling, filtration posed a significant operational risk. Using filtration would also result in significant volumes of water and glucose being lost during sludge discharge.

It was found during reviews that the most appropriate technologies would be dis- solved air flotation and centrifugation.

A disc centrifuge was selected for the process instead of air flotation, because air flotation would require the addition of chemicals to the process, which was unacceptable because of the possibility of food products being contaminated or their taste being changed.

Meanwhile, to separate the water and glucose liquid fractions, the Royal HaskoningDHV team considered nanofiltration and evaporation techniques.

Nanofiltration was considered unreliable, owing to the risk of biofouling because of the presence of glucose, which is highly biodegradable.

Evaporation techniques require a significant amount of energy, despite the technology being more reliable and robust, compared with nanofilters.

A mechanical vapour compression evaporator was selected because of its heat recovery efficiency, with the integration of the evaporation and production processes allowing for the heat recovered from the evaporator to be used for the production process.

This resulted in no additional energy consumption, compared with the previous production process.

The test was scaled up from the lab to a pilot field test, which further proved the efficiency of the disc centrifuge and evaporator in recovering the water and glucose inputs.

Meanwhile, it was also found during the pilot test that pretreatment would be required to prevent particulate matter blockages in the disc centrifuge.

Further, in instances where the evaporator operated at too high a temperature, the glucose would suffer from colourisation, caramelisation and foaming.

The final pilot project was completed in early 2015 and the project is likely to move to full-scale demonstration installation, the success of which could result in this process being rolled out across all Mars’ manufacturing facilities.