When washing equipment operates incorrectly or begins to wear, saleable material can escape into the wastewater stream instead of reaching the stockpile. The result is a chain reaction of operational problems like settlement ponds filling faster, declining water quality, rising maintenance costs, and valuable product loss.
Excess solids in wastewater also increase chemical treatment costs for operations using clarifiers or thickeners. Over time, dirty process water reduces washing efficiency and impacts final product quality. Beyond the operational challenges, producers are also losing material that could otherwise be sold — directly affecting profitability.
Settlement ponds are a common and economical way to handle wastewater. These ponds are large, excavated areas where wastewater containing suspended solids is directed to allow natural settling. Gravity causes suspended particles to gradually sink to the bottom, allowing clearer water from the top of the pond to be recycled back into the washing process.
There are a few signs to watch for that may indicate valuable material is escaping into a pond.
For starters, a sandbar may appear at the discharge point earlier than expected – often the first noticeable sign that something isn’t right.
Equipment issues can also provide visual cues:
Sand buildup accumulating at the back of sand screws.
Finished product changes from cyclones, often an indicator of good material loss.
Aggregate washing equipment tends to deteriorate gradually over time rather than experience a large failure event, so it’s important to stay vigilant and ensure equipment is running in top condition.
Ponds that require more frequent maintenance or cleaning might be another indicator that something has gone wrong. For example, if your pond suddenly needs maintenance every three months, rather than every six months, it’s time to check for a problem.
The use of flocculants – polymer compounds that accelerate the settling of solids in wastewater – is becoming more common in the aggregate industry, particularly in areas with limited space, when production exceeds the capacity of existing ponds, or where conservation is top of mind.
Think of these chemicals like a long spaghetti noodle with either positive or negative charges that attract soil particles with opposite charges. When enough soil particles attach to the polymer chain, the combined mass sinks to the bottom of the vessel or pond, speeding up the settling process.
The proper balance of chemicals is crucial, as too much flocculant and not enough solids may result in the chemical working its way back into wash plant. This can have an especially poor impact on washing equipment like sand screws, which will act like a clarifier with dirt sinking to the bottom of the screw, rather than being washed out.
In regions where water use is at a premium, or where space for a larger settling pond is limited, flocculants are a common choice – but they add expense to operations and must be used diligently.
Preventing valuable material from entering settlement ponds requires attention to detail throughout the production process. Regular monitoring, proper equipment maintenance, understanding material variations, and effective pond management all contribute to keeping saleable product where it belongs – in the stockpile rather than the waste pond. Adopting recommended strategies and practical measures will allow aggregate facilities to function more effectively, reduce financial waste and get the greatest possible return from their valuable resources