What is the fine-grained topic of the following text: It will not surprise you that this month’s newsletter is devoted solely to the mid-Vaal and the complete destruction wrought by the discharge of at least 150 million litres of raw sewage daily into SA’s most important river from Emfuleni’s sewage plants which decant into the Barrage reservoir. Only return the topic.
Environmental damage of the mid-Vaal river due to sewage discharge from Emfuleni's plants.