Caravan parks are seasonal. They are busier at weekends than during the week. They are busier in July than they are in March. So the flow into the wastewater treatment plant will always be variable. A low flow may mean the wastewater has low Dissolved Oxygen. A high flow may lead to overloading of contamination. Often the plant operator has little control over the cleaning products used in the caravans. bleach and other biocides may be used by holiday makers, which will kill the good microbes in the wastewater treatment plant and compromise plant performance.

This caravan park in Cumbria was typical. The bar and restaurant was open all year. The caravan park was open for nine months of the year. Wastewater from the caravans, the toilet block and the restaurant all collected in a holding tank below the carpark. This was then pumped under a road to the Packaged Treatment Plant (PTP) and a soakaway in a field opposite.

Fats collected on the pump and around the walls in the holding tank. This affected performance of the pump. At times of low flow, the wastewater in the PTP was not being allowed to circulate, which lead to malodours.

New owners of the property came across these problems, which got worse as the restaurant and caravan park were improved and became more popular.