As a result of population growth, urbanization, and climate change, public water supplies are becoming stressed, and the chances of tapping new water supplies for metropolitan areas are getting more difficult, if not impossible. As a consequence, existing water supplies must go further. One way to achieve this objective is by increased water reuse, particularly in supplementing municipal water supplies. Although water reuse offers many opportunities it also involves a number of problems. A significant cost for nonpotable water reuse in urban areas is associated with the need to provide separate piping and storage systems for reclaimed water. In most situations, the cost of a dual distribution system has been prohibitive and thus, has limited implementation for water reuse programs. The solution to the problem of distribution is to implement direct potable reuse (DPR) of purified water in the existing water distribution system. The purpose of this paper is to consider (a) a future in which DPR will be the norm and (b) the steps that will need to be taken to make this a reality. Following an overview, the rationale for DPR, some examples of DPR projects, technological and implementation issues, and future expectations are examined.

The state of California has passed legislation to divert organic materials from landfills to reduce the emission of methane to the atmosphere. A large amount of this source separated organic (SSO) material is expected to be used as a feedstock for anaerobic digestion processes. Based on a review of properties for likely SSO feedstocks, it is clear that while SSO are high in volatile solids, they are also concentrated sources of nutrients (principally, ammonium). When SSO feedstocks are digested, these nutrients are released into the digestate, where ammonium can cause problems both within the digester and in downstream treatment processes. The focus of this paper is on the performance of two pilot studies designed to remove ammonia from a digester effluent. The process used in the study is a thermal stripping column with tray configuration, operating under a vacuum. In the first study, food waste digestate was treated as a slurry in the stripping column with and without NaOH addition. At process temperatures near 90 °C, the performance with and without caustic was similar. In the second study, centrate from a co-digestion facility, that blends food processing waste with wastewater process solids, was treated in the same thermal stripping column under the same conditions and without chemical addition. The results from both studies, which can be described using the same performance curves, are presented and discussed in this paper.

In the practice of wastewater treatment system design, process selection is often constrained by factors such as operational costs, performance, and physical footprint. Processes employing colloidal gaseous aphron (CGA) technology have proven to be highly effective for the clarification and thickening of activated sludge mixed liquor, waste-activated sludge (WAS), and anaerobically digested sludge within a small footprint. Technically, an aphron is defined as a gas or liquid phase encapsulated by a surfactant film. Since their initial identification and formulation, aphrons have been used extensively in a number of chemical processes, including gas and oil drilling and food processing waste-treatment applications. The generation and use of CGAs for thickening of WAS and other wastewater applications has been commercialized with the development of the Suspended Air^® flotation (SAF^®) process. The purpose of this paper is to (1) provide background on CGAs flotation technology, (2) identify applications of CGA in wastewater treatment, (3) discuss thickening of WAS with CGA, and (4) present findings from three case studies where WAS thickening with a legacy dissolved air flotation (DAF) process was replaced with a CGA process to increase capacity or address operational challenges, typically within the same flotation tank footprint. The case studies demonstrate the versatility of the SAF^® CGA process for (a) its ability to process the most challenging feedstock, including stored WAS; (b) enhancement of the digestion process and elimination of digester foaming; and (c) high capacity and ease of operation, reducing operation needs.

A urease extract prepared by decanting liquid from a suspension of finely ground Citrullus lanatus (watermelon) seeds was characterized and applied to dilute urine samples to demonstrate a low-cost field method to estimate total Kjeldahl nitrogen (TKN) concentrations in human urine. The extract exhibited a Michaelis-Menten constant, K_m, of 3.00 mM urea and a specific activity of up to 12.2 U/mg protein at an optimum pH of 8.1. A statistical F-test on 54 samples demonstrated that TKN can be estimated as the total ammonium-nitrogen recovered upon addition of urease in dilute fresh and stale urine samples. The total ammonium-nitrogen in urine samples determined after treatment with watermelon seed urease was consistent with that determined using traditional acid digestion techniques. The extract retained 85% of its initial capacity after three months of refrigeration. The effectiveness of this method to assay nitrogen in unbuffered urine samples will be useful in nitrogen analyses in nutrient recovery and urine or slurry storage contexts. Accordingly, this study is useful in understanding the kinetics of a plant-derived urease acting in dilute urine.

To achieve the water quality goals of the future while avoiding major increases in the cost and carbon footprint of wastewater management, it will be...