First thing we have to ask ourselfs is what is Working Capital in general?
Working capital is a financial metric which represents operating liquidity available to a business, organization or other entity, including governmental entity. Along with fixed assets such as plant and equipment, working capital is considered a part of operating capital.
In other words, this is just the cash you use in day-to-day operations.
On the other hand Treasury includes management of an enterprise's holdings, with the ultimate goal of managing the firm's liquidity and mitigating its operational, financial and reputational risk.
In other words, Treasury takes care that there is always enough working capital for day-to-day operations and it looks for ways to make working capital improvements across the organization.
By doing so it might include improving visibility and control, application of the next generation technology, implementation of process standardisation, for example in payments variants or cash flow. Likewise, Risk Management and hedging of future transactions is considered.