Reduction of organic matter containing benzimidazole and toxicity in real livestock wastewater through advanced oxidation processes.

Livestock wastewater (LWW) has a complex characteristic of high organic matter content, metals, nutrients, and pharmaceutical compounds. Advanced oxidation processes (AOP) are a potential option for treating this wastewater. This study evaluated real LWW and the performance of UV/H2O2 and UV/peroxymonosulfate (UV/PMS) for its treatment. The experiments were conducted in a UV photoreactor (16 mW/m2, λ = 254 nm). The oxidant agents (Ox) tested were H2O2 and PMS, each at low, medium, and high TOC/Ox molar ratios. A pretreatment based on chemical precipitation was implemented. Annually, the LWW showed total organic carbon (TOC) values of 859 ± 13.37 mg/L, 168.85 ± 1.62 mg/L of total Kjeldahl nitrogen (TKN), and toxicity of 96% v/v. In the dry season, albendazole (ABZ) (95.3 ± 35.16 mg/L), Cu (4.3 ± 0.23 mg/L), Fe (3.8 ± 0.38 mg/L), and suspended solids (SS) (1015 ± 586.9 mg/L) were identified, so pretreatment was implemented. The UV/PMS process with the lowest molar ratio [TOC/Ox 1:0.75] removed significantly lower TOC concentrations (p < 0.05), but toxicity decreased entirely. The study of mineralization and toxicity provided insight into the changes in LWW during treatment with AOP. Furthermore, it contributed to establishing the technical basis for implementing efficient treatment processes.

Emulating natural wetlands oxygen conditions for the removal of N and P in agricultural wastewaters.

The aim of this research was to evaluate a constructed wetland system (CW) operated under aerobic-anoxic-aerobic conditions to remove C, N and P from water with high concentrations of the last two nutrients. A series of three CW were operated continuously for 190 days. An aerobic vertical CW was used in the first and third stages and an anoxic horizontal CW was used in the second stage. The total nitrogen (TN) removal efficiency was 70 ±â€¯1.5%. Similar removal efficiency behavior was observed in others nitrogen compounds, where a removal of 85 ±â€¯1.5% for NO3--N and 97 ±â€¯2.2% for NH3+N were achieved. The combination of different oxygen conditions enhanced oxidation of nitrates and the assimilation of ammonium by vegetation. On the other hand, 54 ±â€¯6.5% total phosphorus (TP) was removed in the entire system, which is higher than the reported in several investigations, including mechanized and controlled systems such as activated sludge. The phosphorous removal efficiency was attributed to the adequate design and configuration of CW, which facilitated dissolved oxygen (DO) conditions required for phosphorus capture. Despite in this investigation the CW was not designed for an optimal removal of organic matter the removal efficiency of this parameter was 64 ±â€¯7.5%. The successful results suggest that the combination of aerobic-anoxic-aerobic stages is a technically suitable option for the treatment of agricultural wastewater with high content of N and P.

Evaluation of the ultrasound effect on treated municipal wastewater.

In this research, ultrasound (US; 26 kHz) application was evaluated as tertiary treatment of treated municipal wastewater coming from conventional activated sludge (AS) and constructed wetland (CW) systems. The degree of disinfection was evaluated through the total (TC) and faecal (FC) coliforms and by somatic coliphages (SCs) determinations. The experiments were carried out without temperature control at times of 200, 400 and 600 s and with temperature control (298.1 K) at 600, 1200 and 1800 s. Changes in the concentrations of C, N and P were also studied. The results shown that treatment without temperature control allowed 100% inactivation for TC, FC and SC at 600 s, while maximum with temperature was achieved at 1800 s. Temperature was an important factor influencing pathogens inactivation. In both cases, microorganism concentrations complied with different international guidelines for the reuse of treated wastewater. At 1800 s sonication concentrations of biochemical oxygen demand, chemical oxygen demand and total phosphorus were reduced 39.5, 39.4, 50.0 and 37.3% TN in the AS-treated water and 24.0, 49.8, 20.2 and 7.7% in the CW-treated water, respectively. In both cases, the formation of H⋅ and OH⋅ radicals is most likely related to the observed pollutants removal. While energy consumption of ultrasound was higher than other advanced treatments such as electrocoagulation, its implementation allows the simultaneous removal of pathogens and organic pollutants without the generation of toxic by-products. In conclusion, ultrasound can be implemented as tertiary treatment of municipal wastewater for the removal of biological and organic pollution, according to reuse guidelines in terms of pathogens presence.