By Nicholas Earl Water utilities loaded with debt are at a growing risk of collapse as interest rates rise, argued David Black, chief executive of Ofwat. The boss of the industry regulator revealed feared that utilities have piled on debt could go under, piling further pain on households at a time when bills are already soaring. Black told The Sunday Times that Ofwat was keeping a close eye on the impact of rapid rate increases from the Bank of England, which could heap costs on highly leveraged water companies. Commenting on the affects of interest rates, he said: “We tend to see the cost of …