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Recycling of Cooling Water Using Ultrafiltration Membrane at Sakata

The Challenge

Sakata, a rice cracker manufacturer, investigated ways of reducing water demand during their manufacturing process. It was recognised that 40 per cent of water use occurs during the dough cooling process, in which water cools and lubricates hot dough as it leaves the oven. To enable the reuse of dough water a technology capable of removing starch whilst maintaining water quality was required. After a successful pilot, Sakata have installed an ultrafiltration system that is expected to save 24 million litres a year.

The Project

Water is an important part of the dough cooling process and its use cannot be avoided. Investigations were therefore focussed on how water use could be minimised during the process. The taps in the dough cooling area were adjusted to trickle water on the surface of the dough as an initial step in achieving minimal water usage.

The second major task was investigating water reuse. Good water quality in the dough cooling process is particularly important to final product quality. A large number of water quality tests were conducted on the dough water to identify what pollutants would hinder reuse. While water was generally of a good quality, testing revealed low limits of starch and total plate counts were in excess of the sites stringent quality requirements.

Sakata engaged Veolia to conduct research and pilots on possible filtration units to treat the water to an acceptable reuse standard. With funding assistance from City West Water, Veolia conducted research and pilots on possible filtration units that would remove starch and lower the total plate count.

A microfiltration unit was initially trialled, however build up of starch over time resulted in continuous fouling of filters. Ultrafiltration was trialled next. Again starch built up over time, however the more robust membrane was able to withstand chemical cleaning techniques which removed the fouling material. Based on successful trials a full scale system was investigated.

To ensure the system was sufficiently robust to meet Quality Assurance requirements, additional steps to ensure pathogen kill where included in the treatment train. These involved ultra violet light, and chlorine treatments of the recycled water.

The Outcome

A feasibility study on up-scaling the project was presented to City West Water, who assisted in co-funding two large ultrafiltration units to service Sakatas five production lines. Production using the new ultrafiltration units commenced late 2011. The system installation is expected to reduce water consumption by 24 million litres per year with similar reductions to trade waste volumes at the site.