Excessive discharges of phosphorus in treated wastewater and urban and agricultural runoff can choke lakes, rivers, and bays with algae. In addition to their foul odor and unsightly appearance, these algae deplete the oxygen supply in the water, killing fish and other aquatic organisms, and release toxins that can force shutdowns of water treatment plants that provide water for human consumption. Application of HAOPs technology as a tertiary treatment can remove phosphorus from wastewater to almost any target level, while simultaneously removing residual organic matter and color, with minimal expenditure of energy. The process is highly robust, responding instantaneously and automatically to changes in feed composition and flow rate.