Effects of Sewage Discharge on Trophic State and Water Quality in a Coastal Ecosystem of the Gulf of California

Abstract

This paper provides evidence of the effects of urban wastewater discharges on the trophic state and environmental quality of a coastal water body in a semiarid subtropical region in the Gulf of California. The concentrations of dissolved inorganic nutrients and organic matter from urban wastewater primary treatment were estimated. La Salada Cove was the receiving water body and parameters measured during an annual cycle were temperature, salinity, dissolved oxygen, nitrite, nitrate, ammonia, orthophosphate, and chlorophyll a. The effects of sewage inputs were determined by using Trophic State Index (TRIX) and the Arid Zone Coastal Water Quality Index (AZCI). It was observed that urban wastewater of the city of Guaymas provided 1,237 ton N yr−1 and 811 ton P yr−1 and TRIX indicated that the receiving water body showed symptoms of eutrophication from an oligotrophic state to a mesotrophic state; AZCI also indicated that the environmental quality of the water body was poor. The effects of urban wastewater supply with insufficient treatment resulted in symptoms of eutrophication and loss of ecological functions and services of the coastal ecosystem in La Salada Cove.

Reduction in toxicity of wastewater from three wastewater treatment plants to alga (Scenedesmus obliquus) in northeast China

“…Acute toxicity evaluation for municipal wastewater has also been conducted in recent years with aquatic organisms, such as luminous bacteria, algae and fish (Mendonca et al, 2013;Ma et al, 2013Ma et al, , 2005. Some investigations revealed that municipal wastewater could induce eutrophication of its receiving water body with the blooming of algae growth (Vargas-Gonzalez et al, 2014;Bayram et al, 2013). Although there are many researches on contaminants removal from wastewater during its treatment process, studies on the toxicity removal of wastewater are still limited (Mendonca et al, 2013;Ma et al, 2013;Zhao et al, 2014;Zhang et al, 2013a).…”

Assessment and remediation of pollutants in Ghana's Kete-Krachi District Hospital effluents using granular and smooth activated carbon

“…Moreover, for all the GAC treatment weeks, the DO value improved only about 1.9 times. Essentially, the lower DO values (<3 g/L) in the RSW2 and RSW3 reflect the hypoxic activities which adversely affect aquatic lives and the environment [39] .

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“…The DO values mg/L indicate that the anaerobic activities in the effluent caused by anaerobic organisms such as bacteria were enormously reduced after treatment since sufficient oxygen decreases anaerobic decomposition of the organic matter [33] . Therefore, the treated effluent has enough oxygen capacity to absorb and digest the organic waste it receives [39] .…”

Concerns and Threats of Contamination on Aquatic Ecosystems

“…Fresh water sources "serve as best sinks for the discharge of these wastes" (Das and Acharya 2003;Tukura et al 2009). It is estimated that "58% of the wastewater from urban areas and 81% of industrial wastes are discharged directly into water bodies with no or inadequate treatment results in contamination of ~73% of the water bodies" (Vargas-Gonzalez et al 2014). The release of "sewage has led to the increase in water pollution and depletion of clean water resources" (Avalon Global Research 2012).…”