Trade waste compliance is a condition of operating for most food and beverage manufacturers that discharge to sewer. A trade waste approval from the local water utility sets limits on what the plant can discharge, and charges are typically linked to how much is discharged and how strong it is. Production, however, does not generate wastewater evenly: cleaning cycles, product changeovers and spills create peaks in flow, pH and organic load that are difficult to manage by hand.
Where trade waste problems arise
The most common difficulties for food and beverage plants are:
- pH excursions from cleaning chemicals, outside the approved range
- Load peaks when product, sugar or fat reaches the drain during changeovers and cleaning
- Temperature from hot washdown water and process discharges
- Fats, oils and grease that exceed limits when pre-treatment is overloaded or poorly maintained
- Incomplete records of what was discharged and when
Urban Utilities’ trade waste acceptance criteria illustrate the kind of limits involved, including a pH range of 6 to 10.5 and limits on biochemical oxygen demand (BOD) and grease and oil. Its trade waste environmental management plan notes that approvals may require pre-treatment, pH control, flow monitoring and sampling facilities. Other Queensland utilities apply their own criteria, and your approval sets the limits that apply to your site.
Why manual management falls short
The person responsible for trade waste is rarely watching the drain. Peaks occur during cleaning at the end of a shift or during a changeover, when attention is on production. Pre-treatment equipment such as balance tanks and grease arrestors only works if it is operated consistently: tanks emptied at the right rate, pumps running when needed and alarms acted on.
Automated trade waste compliance control
The control system manages flow from a balance tank, holds pH in range, monitors discharge quality and records it.
How it works
- 1
Balance
Wastewater collects in a balance tank. A variable speed discharge pump releases it at a steady rate, smoothing out the peaks from cleaning and changeovers.
- 2
Correct pH
pH is measured and corrected by metered dosing in the tank, so discharges stay within the approved range.
- 3
Monitor
Flow, pH and temperature are measured continuously at the discharge, with alarms on any parameter approaching its limit.
- 4
Record
Flow and quality are logged continuously, giving the site a complete discharge history.
One contract, every trade licensed
Trade waste work connects to the sewer and must be done by licensed plumbers. Plumbing and drainage, including tanks and sewer-side pumps and pipework, is carried out by a QBCC-licensed plumbing contractor that we engage and manage. We carry out the electrical, instrumentation and controls work under QLD Electrical Contractor Licence 1513082. One contract and one accountable lead covers the whole system. For plants whose main issue is pH alone, see washdown pH control.
The commercial case
The benefits are reduced risk of exceedances, more predictable trade waste charges where they depend on volume and strength, and records that make discussions with the utility straightforward.
Alternatives
- Manual monitoring and dosing. Low capital cost, but dependent on staff attention at exactly the times production is busiest.
- Process changes. Reducing product loss to drain is always worthwhile, and complements automated treatment control.
- Packaged treatment systems. Suitable for some sites. Integration with existing equipment, cleaning schedules and records is where a site-specific design adds value.
- Separate contractors. An electrician, plumber and controls contractor engaged separately leave coordination and accountability with the site.