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Synthetic wastewater prepared from readily available materials: Characteristics and economics [1]

['Abigail K. Kargol', 'School Of Environmental', 'Forest Sciences', 'University Of Washington', 'Seattle', 'Washington', 'United States Of America', 'Samantha R. Burrell', 'Indrajit Chakraborty', 'Heidi L. Gough']

Date: 2023-11

The wastewater used for experimental research is typically collected from a wastewater treatment plant or prepared as a synthetic solution in the lab. These options represent transportation and cost challenges, respectively, particularly for experiments requiring large volumes of wastewater. Here, we describe a method for creating inexpensive synthetic wastewater from readily available household products. The base solution, synthesized by soaking dog food pellets for 24 hours and straining the solution, had average nutrient values of 9.7 mg/L ammonia as N, 12.2 mg/L nitrate as N, 227 mg/L total nitrogen, and 4870 mg/L chemical oxygen demand (COD). Degradation tests demonstrated that soluble COD was biodegradable. The base solution was then used to prepare synthetic wastewater that met the requirements for two experimental applications; (1) anaerobic treatment of primary effluent and (2) land-application treatment of secondary effluent. Cost analysis indicated that the single-ingredient synthetic wastewater cost 92% less to produce than synthetic wastewater recipes that used laboratory chemicals, and reduced preparation time. These results demonstrated that use of commercial products can simplify the wastewater synthesis process and reduce experimental costs for large-volume research applications while still maintaining consistent wastewater characterization.

Funding: This work was supported in part by the McIntire-Stennis Cooperative Forestry Program grant no. NI20MSCFRXXXG040/project accession no. 1017343 from the USDA National Institute of Food and Agriculture (HLG). AKK was funded through the University of Washington, College of the Environment Graduate Research Opportunity Enhancement (GROE) Program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2023 Kargol et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

1 Introduction

Synthetic wastewater (SWW) has long been used in wastewater research [1]. It is used when a predictable wastewater composition is required [2–4]. SWW is also used when access to a wastewater treatment facility is limited [5] or year-round access and transport are not realistic [6]. Most SWW recipes include many chemical components and can be time-consuming and costly to prepare [7, 8]. Recipes commonly include peptone, meat and yeast extracts, cellulose, casamino acids, urea, and various trace elements to simulate the complex mixture of carbon and nutrients found in real wastewater [6, 9]. For studies that require large volumes of wastewater [8, 10–12], producing a steady supply of synthetic wastewater could become a challenge.

Published SWW recipes vary in their characteristics and limitations. For example, the Organization for Economic Co-operation and Development (OECD) [9] has published a standard method for preparation of SWW that includes peptone, meat extract, urea, and trace elements [9], which they recognize to contain higher nitrogen, and lower carbon (as chemical oxygen demand, COD) content than typical wastewater. The recipe for another SWW (“SYNTHO”) uses similar components but in different proportions, resulting in a COD to total N ratio of 7.3:1 [7]. A review by Prieto et al. [6] of 24 other SWW recipes found that most are either based on one of the recipes above or are unique to individual studies. These recipes are generally prepared with a large number of ingredients to create well-defined synthetic wastewater. The use of unique recipes or significant modification of existing formulas suggests that the standard recipes are not able to meet the experimental needs for all wastewater studies.

Preparation cost is also a barrier, which is stated in the ASTM SWW recipe protocol [13]. Some recipes replace laboratory chemicals with less expensive commercial products such as whey, milk powder, soybean oil [6, 14] or molasses [15]. Others have utilized waste products, including watermelon peels [16], cheese whey water, and sweet potato extract [17] to reduce costs. Additionally, when organic material is added to synthetic wastewater as simple carbon sources such as glucose, sucrose, or acetate [5], it does not replicate the complex mixture of compounds in real wastewater. Components such as trace organics and metals may also be omitted [18]. In all cases, the SWW requires multiple chemical components, which additionally introduces a preparation time barrier.

In this paper, we describe the development of a SWW recipe using dry dog food as the base ingredient. Commercially available dog food has previously been explored as a way to simulate biosolids [15] and food waste [3], and to increase particulate concentration in colloidal wastewater [19], but has not been used as the main carbon and nitrogen source in a synthetic wastewater. The formulation of dog food combining protein, fats, and simple carbohydrates makes this an ideal candidate for SWW. Using the dog food SWW (DSW) base, we evaluated the addition of supplemental household and laboratory chemicals to achieve the characteristics needed to satisfy different experimental requirements. Cost analysis was conducted to compare the new DSW formula with the OECD standard method for synthetic wastewater preparation. This simplified synthetic wastewater recipe offers a novel approach for cost and preparation time challenges that will advance research capabilities for large volume bioreactor testing and for easier transportation to remote field-scale biological treatment testing sites.

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[1] Url: https://journals.plos.org/water/article?id=10.1371/journal.pwat.0000178

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