Sewage sludge

A considerable amount of sewage sludge is being spread on barley stubble in the municipality of Motilla del Palancar. Are there any restrictions on applying this waste to farmland (these plots will possibly be sown with lentils in the next growing season)? What controls are in place to determine if this product contains heavy metals or other contaminants, such as viruses, that could affect the human population?

There are manure management companies that mix extensive livestock manure with sewage sludge. Are there any limits on the quantities that can be mixed? Are these companies required to inform farmers about the mixture they sell?