The Journey from Dilution to Zero Liquid Discharge

Estimated reading time: 2 minutes

Editor’s note: To address this topic in a manageable way, all examples and explanations will be hung on a framework that assumes a new build on a greenfield site. GreenSource Engineering is aware that in many cases, the customer already has a wastewater solution and therefore only needs an end-of-pipe solution (EOP) to achieve zero liquid discharge (ZLD) or minimum liquid discharge (MLB). A case study will be used for explanation.

If you’re familiar with the PCB industry, and a little long in the tooth like me, you may remember the cry, “The water board is here!” (or an equivalent authority). This was the signal for a frantic but regularly rehearsed exercise to turn on all the rinses. This anecdote demonstrates that in the early days of PCB production, prevailing practices revolved around a “dilution is the solution” mentality, in which manufacturers used copious amounts of water to dilute contaminants before discharging them into regulated municipal wastewater systems or natural water bodies.

This approach, while superficially addressing immediate discharge requirements, failed to consider the long-term environmental consequences of such practices, leading to growing awareness of pollution and its effects on public health and ecosystems. As the mg/L unit changed to mg/day, the tightening of industrial regulations to align with environmental concerns became paramount. These more stringent regulations led directly to more technological approaches to wastewater treatment.

In addition to the water regulations making significant wastewater investment obligatory, the increasing water costs fueled a water-saving mindset. This enforced investment without a viable ROI was coupled with potentially poor rinsing, which then needed to be addressed. That solution was water recycling. Initially, the industry stumbled through a series of inefficient, expensive solutions and ultimately could not produce water that supported the more sensitive, chemically based processes, such as electroless final finishing.

To continue reading this article, which appeared in the April 2026 I-Connect007 Magazine, click here.