The application of pinch analysis for the rational management of water and effluent in an industrial complex (1996)

Funded by: Water Research Commission

Partner organisations: Partners in Development, eThekwini Water and Sanitation

Project description
The damaging effect of the chemical process industry on the environment is one of the greatest challenges facing industry throughout the world. Although industry accounts for only approximately 16 % of the direct water use in South Africa, it often produces effluents, which contain toxins and other damaging pollutants. The damaging effect of industry in South Africa is compounded by a low availability of water. The reduction of both the consumption of water and production of effluent by this economic sector is of vital importance to the protection of South Africa's water resources and environment. The above factors have resulted in wastewater minimisation becoming an important environmental issue
to South African industry. 

Preventing pollution requires designs that are intrinsically eco-efficient, and not designs that rely on end-of-pipe treatment. In order to implement cleaner production designs, the designer requires methods to investigate the implications of the various design possibilities. Process integration is a holistic approach to process design, retrofitting, and operation which emphasises the unity of a process.

Raw water is pre-treated before use in various processes such as washing, (e.g. vessel cleaning). In these processes water comes into contact with process materials, becomes contaminated, and is sent to wastewater treatment. Freshwater (treated raw water) may be upgraded in boiler feed water (BFW) treatment for use in the steam system. Wastewater is generated by ion-exchange regeneration, boiler blow down and condensate loss. Another source of wastewater is the cooling tower blow down. The various wastewater streams are then typically mixed, along with contaminated storm water, and sent to treatment. 

Industrial processes thus require water with a range of qualities, and produce a range of effluents, which allow the possibility of a hierarchical use of water.
Possible strategies for reducing the production of wastewater include:
  • reuse: wastewater from one process can be directly reused in others, provided the level of contamination is sufficiently low to meet the requirements of the subsequent processes;
  • regenerative reuse : wastewater can be treated to reduce the levels of contaminants before being reused in other processes. In this option, the water is not recycled to the process from it came;
  • regenerative recycling: after regeneration, water can be recycled to the process from which it came. This is generally more difficult than reuse, because recycling tends to build up contaminants.
Project Objectives
  • To apply and assess the Water Pinch technology and approach for promoting water and effluent conservation in a chemical complex.
  • To apply the technique to the AECI Umbogintwini site.
  • To make any necessary refinements to the technique.
  • To transfer the technology to AECI management, water authorities, consultants and academics.
  • To train engineers with the ability to undertake formal water and effluent conservation surveys