Comparative Mammalian Cell Cytotoxicity of Wastewaters for Agricultural Reuse after Ozonation

Abstract

Reusing wastewater in agriculture is becoming increasingly common, which necessitates disinfection to ensure reuse safety. However, disinfectants can react with wastewater constituents to form disinfection byproducts (DBPs), many of which are toxic and restrict the goal of safe reuse. Our objective was to benchmark the induction of mammalian cell cytotoxicity after ozonation against chlorination for three types of real wastewaters: municipal secondary effluent and two sources of minimally treated swine farm wastewaters. A new method to evaluate samples of suspected high cytotoxicity was devised. For the secondary effluent, ozonation reduced the cytotoxicity by as much as 10 times; chlorination lowered the cytotoxicity only when followed by dechlorination. The swine farm wastewaters were up to 2000 times more cytotoxic than the secondary effluent, and the highest reduction in cytotoxicity was 17 times as achieved by ozonation. These results indicate that secondary effluent is preferred over swine wastewaters for agricultural reuse regardless of the tested disinfectants. Ozonation consistently reduced the cytotoxicity of both the full strength and the organic extracts of all tested wastewaters more than chlorination. The only significant correlation was observed in the secondary wastewater between total haloacetonitriles and cytotoxicity. While the association of reduced toxicity with the modification or reduction of specific compound(s) is unclear, regulated DBPs may not be the primary forcing agents.

Organohalogens Naturally Biosynthesized in Marine Environments and Produced as Disinfection Byproducts Alter Sarco/Endoplasmic Reticulum Ca2+ Dynamics

“…29,30 Remarkably, high levels of several halopyrroles, including tetrabromopyrrole ( 31 ), are produced as disinfection byproducts (DBPs) during treatment of drinking water, agricultural irrigation water and saline wastewater, and are considered as emerging pollutants because of their cytotoxicity, genotoxicity, carcinogenicity and developmental toxicity. 31–35 For example, 31 is a prominent byproduct of chlorination of seawater for sewage-treatment in coastal areas and exhibits potent developmental toxicity to Platynereis dumerilii embryos. 34 Another DBP first identified in Israeli drinking water, 2,3,5-tribromopyrrole ( 34 ), is produced during sewage treatment protocols utilizing both chlorine and seawater that are common in coastal communities, and is genotoxic and cytotoxic to CHO (Chinese hamster ovary) cells.…”

Human health trade-offs in the disinfection of wastewater for landscape irrigation: microplasma ozonation vs. chlorination

“…3 Lowered water toxicity after ozonation has also been reported. 18 Recently, an emerging method to produce ozonemicroplasma technologywas invented and brought to market. 19 Because the building block of microplasma ozone generators (known as a "chip") is modular and produces 2-3 grams of ozone per hour, virtually any ozone production rate can be generated by stacking individual chips.…”

Disinfection Byproduct Recovery during Extraction and Concentration in Preparation for Chemical Analyses or Toxicity Assays

“…While THMs and HAAs have been used to measure DBP exposure for epidemiology studies, there is growing interest in measuring unregulated (semi-)­volatile classes (e.g., haloacetonitriles) based on studies indicating that they could contribute more to the cytotoxicity of disinfected waters and that their concentrations do not correlate with THM concentrations . Recoveries of unregulated, (semi-)­volatile DBPs were lowest for XAD resin extraction (<30%), one of the most frequently employed techniques, ,− , including the U.S. EPA studies. , While recoveries were generally higher with SPE and LLE, they were below 70% for most of the (semi-)­volatile DBPs examined. Even these mediocre recoveries required solvent exchange, risking the potential for toxicity associated with incomplete removal of MtBE or EtOAc from the DMSO during N 2 blowdown.…”

“…Even these mediocre recoveries required solvent exchange, risking the potential for toxicity associated with incomplete removal of MtBE or EtOAc from the DMSO during N 2 blowdown. Recoveries of most unregulated, (semi-)­volatile DBP classes would be negligible for XAD resin extraction coupled with EtOAc elution when the EtOAc is evaporated nearly to complete dryness before resuspension in DMSO. ,− , …”

“…As most DBPs occur at relatively low concentrations (ng/L to μg/L levels) in disinfected water, extraction and concentration are needed to identify novel DBPs and facilitate the detection of biological effects in toxicity assays. Solid-phase extraction (SPE) using XAD resins has been used extensively to extract and concentrate DBPs in disinfected waters for bioassays, ,− including a standard operating procedure for studies by the U.S. EPA . XAD resin extraction typically involves passing ≥10 L of disinfected water through a mix of XAD-2 and XAD-8 resins, eluting the sorbed compounds with ethyl acetate, and concentrating the extract to ≤1 mL using rotoevaporation and nitrogen (N 2 ) blowdown .…”