Water Savings in Sugar Refining Zimbabwe - Full scale

MANUFACTURE OF FOOD PRODUCTS AND BEVERAGES # 48

Background

The Zimbabwe Sugar Refining Corporation operates two sugar refineries in Harare and Bulawayo. The refineries receive raw sugar from sugar cane mills, and further process it into refined, white sugar. White sugar is produced for the local market and for regional export. The Harare plant was established in 1953. The main equipment dates back to the same period. The factory runs seven days a week, twenty-four hours a day and has a yearly production of 140,000 tons of refined sugar. The factory employs approximately 500 people. This case study follows the assessment in the Harare factory.

The focus of the CP assessment was on water conservation, as a long drought had resulted in severe water shortage and rationing in Zimbabwe. The sugar refinery was faced with high surcharges when the water consumption level exceeded the allocated amount.

The most significant sources of water loss included the following:

Approximately 42 m3 of fresh water used daily to wash the bagasse originating from the clarifier into the sewage system;
An overflow of 264 m3 per day from an insufficient water storage capacity from the cooling towers, due to the increase in the capacity of the evaporation tanks;
Use of 216 m3 of fresh water to wash the charhouse (an older method for decolorization using bone char)

Cleaner production (CP) measures were implemented with assistance from National Cleaner Production Centers (NCPCs)

Cleaner Production Principle

New technology, Recovery, reuse and recycle

Cleaner Production Application

The following CP solutions have been implemented:

A water softener and additional piping were commissioned to recycle water as "sweet water" in the melting pot at the start of process;
The bagasse generated at the clarifiers is now put through a press filter and used for agricultural purposes, instead of being discharged into the sewage system. The water is recycled as "sweet water" in the melting pot;
Water meters were installed to improve water management at units with high water consumption.

The option to redirect the overflow from the cooling towers to the production process is under investigation.

Environmental and Economic Benefits

The implementation of the three options is projected to reduce the water consumption by approximately 86,000 m3 annually. Solid wastes to the municipal sewer is projected to be reduced by 120 tons per year.

The factory invested US$ 28,000 for the reduction of water consumption. With an expected saving of US$ 24,000 per year on water charges, pay-back will be 14 months (not considering any possible surcharges for which they may have been responsible).

Constraints

None reported.

Contacts

Mr. Harrison
Zimbabwe Sugar Refineries
47 Douglas Road
Workington
P.O. Box ST 396
Southerton
Harare, Zimbabwe
Tel: +263 4 620911; Fax: +263 4 620902
 
Mr. Lewin Mombemuriwo, Director
Zimbabwe Cleaner Production Center
Takura House, 1st floor
Union Avenue
Harare, Zimbabwe
Tel: +263 4 731778/9; Fax: +263 4 731779
e-mail: cpczim@harare.iafrica.com
 
UNIDO
NCPC Program
Environment and Energy Branch
P.O. Box 300
A-1400 Vienna, Austria
Tel: +43 1 26026 4696; Fax: +43 1 26026 6803
e-mail: ncpc_env@unido.org
Internet: http://www.unido.org
 
UNEP IE
Cleaner Production Program
Tour Mirabeau
39-43, quai Andrť-CitroŽn
75739 Paris Cedex 15, France
Tel: +33 1 44371450; Fax: +33 1 44371474
e-mail: uneptie@unep.fr; Web: http://www.uneptie.org/home.html

Review Status

This National Cleaner Production Center case study was presented in the document "NCPC Case Studies" available from UNEP IE or UNIDO (addresses above). It was formatted and edited for the ICPIC diskette in August 1997.  

Subsequently a technical review was done by Dr. Prasad Modak, Environmental Management Centre, Mumbai, India in September 1998.