Numerical Analysis of a Full-Scale Thermophilic Biological System and Investigation of Nitrate and Ammonia Fates

Abstract

Thermophilic biological processes proved to be effective in aqueous waste (AW) and high-strength wastewater treatment. In this work, the monitoring of a full-scale aerobic thermophilic biological plant treating various high-strength AW in continuous mode is reported. This paper aims to: (i) provide models to help the AW utility manager in predicting the load of fed pollutants and performances, and (ii) fully investigate nitrogen transformations in biological reactor. Based on the results, the thermophilic sludge in the studied plant was able to degrade Chemical Oxygen Demand (COD) and remove nitrate nitrogen with very high efficiency (79.3% and 97.1, respectively). The monitoring was conducted following a statistical approach and searched for the possible correlations between the input parameters and the efficiency of removal of the plant. Moreover, a multivariate linear regression was carried out highlighting that the yield value of the removal of COD and nitrogen forms, apart from ammonia, was well explained (R2 = 0.9) by the linear regression against the other monitored parameters. As far as nitrification is concerned, there was, on the one hand, an increase in ammonium ions due to the hydrolysis of the organic substance that occurs in the reactor, and on the other hand, a stripping of the same ammoniacal nitrogen in the form of NH3. While nitrates were effectively removed, according to fluorescent in situ hybridization tests, sludge proved to be formed by minute flocs, where bacteria responsible for the oxidation of ammonium and nitrite seem to be unable to grow.

Statistical Characterization of Full-Scale Thermophilic Biological Systems to Inform Process Optimization

“…To obtain reliable modeling, the data were normalized by the maximum value of the series to obtain a series of homogeneous values between 0 and 1 [17]. Pearson and Spearman rank correlations were used to calculate the binary correlations between the nitrogenous forms monitored within the plant.…”

“…By observing the value in kg/week of each parameter output from the TMR it is possible to note the high removal yields shown subsequently in Table 1. The only parameter which has an output load value higher than the input is ammonia due of the strong ammonification process of organic nitrogen in thermophilic conditions [17]. The trend of the distribution of outgoing loads divided into the 6 years shown is instead useful for showing a second strong point of this technology [32].…”

“…The great elasticity of this treatment makes it suitable to be applied to different substrates in terms of both chemical and rheological characteristics [16]. This technology has demonstrated resistance to some conservative parameters and micropollutants and it has been applied in two full-scale plants [17]. As a matter of fact, TMR combines the robustness of physico-chemical treatments with the advantages of biological ones, thus allowing a production of equivalent CO 2 lower than standard physico-chemical treatments [18].…”

Assessment of the Impact of a New Industrial Discharge on an Urban Wastewater Treatment Plant: Proposal for an Experimental Protocol

“…OUR and AUR tests, whose important applicability has been demonstrated in many previous studies [2,[25][26][27][28][29], were inevitably included in the protocol structure to study the impact of different substrates on the autotrophic and heterotrophic mesophilic biomass of the urban WWTP. In particular, the aim was to evaluate the effect of the ID on the biological activity of the CAS system.…”

Coupled Photocatalysis and Microalgal–Bacterial Synergy System for Continuously Treating Aquaculture Wastewater Containing Real Phthalate Esters

“…Although no immediate health risks were discovered to be associated with consumption of these shrimps, the finding indicates that PAEs must be removed from real aquaculture wastewater. In future research, we will collect more data and think of using Spearman and Pearson correlation matrices [30] to analyze the correlation between parameters and phthalate esters.…”