Sentence:  The high cost of land and a few operational problems resulting from excessive loadings have created the need for a wastewater treatment system with the operational characteristics of the oxidation pond but with the ability to <WSD>treat</WSD> more organic matter per unit volume . 
Meaning of the word marked with <WSD> tags:  subject to a process or treatment, with the aim of readying for some purpose, improving, or remedying a condition