Successful solution for high nitrogen content wastewater treatment from rendering plants

Coronavirus disease 2019 (COVID-19) and its spread prevention actions (SPAs) have affected a large number of human activities globally in 2020-2021. Temporary lockdowns, stay-at-home policies, movement restrictions, and personal health care actions have relatively changed the daily life routine in urban areas which can eventually affect the characteristics of municipal wastewater (MW). This study evaluates the performance of wastewater treatment plants (WWTPs) during COVID-19 pandemic and related SPAs. This evaluation also considers MW variations in quality and quantity and compares the performance of WWTPs (2020) with earlier data (2015–2019). For this purpose, 23 WWTPs located in Isfahan province, Iran, were chosen as the study area and classified based on their locations, biological treatment unit, and capacities. Results indicate that the inflow of WWTPs increased 20 % on average during SPAs, while the concentrations of COD and BOD in MW decreased 23 and 16 %, respectively. Nevertheless, the performance of WWTPs remained rather constant. It is concluded that increasing the dilute domestic proportion of MW, particularly in smaller communities, as a matter of COVID-19 SPAs could not impose adverse impacts on wastewater treatment operations and pollution removal. Different types of secondary treatment units, such as activated sludge, stabilization pond, and aerated lagoon showed stable performances. However, disinfection was enhanced in WWTPs in order to reduce the probability of viral transmission via wastewater for reuse. This study also recommends that the characteristics of MW, and not treated wastewater, can be used as an indicator for coordinating SPAs in similar epidemics. This notification can be helpful for the management of WWTPs and risk control in urban areas.

The rapid identification of the amount and characteristics of chemical oxygen demand (COD) in influent water is critical to the operation of wastewater treatment plants (WWTPs), especially for WWTPs in the face of influent water with a low carbon/nitrogen (C/N) ratio. Given that, this study carried out batch kinetic experiments for soluble chemical oxygen demand (SCOD) and nitrogen degradation for three WWTPs and established machine learning (ML) models for the accurate prediction of the variation in SCOD. The results indicate that four different kinds of components were identified via parallel factor (PARAFAC) analysis. C1 (Ex/Em = 235 nm and 275/348 nm, tryptophan-like substances/soluble microbial by-products) contributes to the majority of internal carbon sources for endogenous denitrification, whereas C4 (230 nm and 275/350 nm, tyrosine-like substances) is crucial for readily biodegradable SCOD composition according to the machine learning (ML) models. Furthermore, the gradient boosting decision tree (GBDT) algorithm achieved higher interpretability and generalizability in describing the relationship between SCOD and carbon source components, with an R2 reaching 0.772. A Shapley additive explanations (SHAP) analysis of GBDT models further validated the above result. Undoubtedly, this study provided novel insights into utilizing ML models to predict SCOD through the measurements of the excitation–emission matrix (EEM) in specific Ex and Em positions. The results could help us to identify the degradation and transformation relationship between different kinds of carbon sources and nitrogen species in the wastewater treatment process, and thus provide a novel guidance for the optimized operation of WWTPs.

Performance of full-scale rural wastewater treatment plants in the reduction of antibiotic-resistant bacteria and antibiotic resistance genes from small-city effluents

Many of Egypt's cities have existing treatment plants under operation that have been constructed before 1970. Almost all of these treatment plants now need rehabilitation and upgrading to extend their services for a longer period. One of these plants is the Beni Suef City Wastewater Treatment Plant. The Beni Suef WWTP was constructed in 1956. It has primary treatment followed by secondary treatment employing intermediate rate trickling filters. The BOD, COD, and SS concentration levels are relatively high. They are approximately 800, 1100, and 600 mg/litre, respectively. The Beni Suef city required the determination of the level of work needed for the rehabilitation and upgrading of the existing 200 l/s plant and to extend its capacity to 440 l/s at year 2000 A description of the existing units, their deficiencies and operation problems, and the required rehabilitation are presented and discussed in this paper. Major problems facing the upgrading were the lack of space for expansion and the shortage of funds. It was, therefore, necessary to study several alternative solutions and methods of treatment. The choice of alternatives was from one of the following schemes: a) changing the filter medium, its mode of operation and increasing the number of units, b) changing the trickling filter to high rate and combining it with the activated sludge process, for operation by one of several possible combinations such as: trickling filter-solids contact, roughing filter-activated sludge, and trickling filter-activated sludge process, c) dividing the flow into two parts, the first part to be treated using the existing system and the second part to be treated by activated sludge process, and d) expanding the existing system by increasing the numbers of the different process units. The selection of the alternative was based on technical, operational and economic evaluations. The different alternatives were compared on the basis of system costs, shock load handling, treatment plant operation and predicted effluent quality. The flow schemes for the alternatives are presented. The methodology of selecting the best alternative is discussed. From the study it was concluded that the first alternative is the most reliable from the point of view of costs, handling shock load, and operation.

This paper addresses the implementation of economic-oriented model predictive controllers for the dynamic real-time optimization of the operation of wastewater treatment plants (WWTP). Both the economic-optimizing controller (pure-EMPC) and the economic-oriented tracking controller (Hybrid-EMPC, or HEMPC) formulations are validated in the benchmark simulation model (BSM1) platform that represents the behavior of a characteristic activated sludge process. The objective of the controllers is to ensure the appropriate operation of the plant, while minimizing the energy consumption and the fines for violations of the limits of the ammonia concentration in the effluent along the full operating period. A non-linear reduced model of the activated sludge process is used for predictions to obtain a reasonable computing effort, and techniques to deal with model-plant mismatch are incorporated in the controller algorithm. Different designs and structures are compared in terms of process performance and energy costs, which show that the implementation of the proposed control technique can produce significant economic and environmental benefits, depending on the desired performance criteria.

Dynamic modelling and simulation is increasingly being employed as an aid in the design and operation of wastewater treatment plants (WWTPs). In this paper a simulation model is used to investigate control of an activated sludge process (ASP). It is shown how the recycle and wastage flow rate variables can be employed to continually maintain plant operation in the presence wastewater load disturbances and plant changes. Considerations are also given as to how plant operation could be optimised in order to increase treatment capacity and reduce operating costs.

The present study has been undertaken to evaluate the performance of wastewater treatment systems (WWTS) in three different districts (Kolkata, Howra and Hugli) in West Bengal, India. Performance of these wastewater treatment plants are essential parameter to be monitored as the treated effluent is discharged into River Ganga which is the National River of India. The performance evaluation will also help for the better understanding of design and operating difficulties in wastewater treatment plants. The performance evaluation was done on the basis of removal efficiency of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), Total Coliform (TC) and Fecal Coliform (FC). The performance of prevailing oxidation pond and activated sludge process type was good in terms of BOD, COD and TSS removal. Even though the removal efficiency of total and fecal coliform was high (85-98%), none of the plants meet the coliform discharge standards because of the high incoming TC and FC.

The COVID-19 pandemic is considered one of the most significant threats to health. The effect of the pandemic on performance of wastewater treatment plants has not received much attention in the literature. This study assessed the impact of Coronavirus pandemic on the wastewater quantity, characteristics, treatment processes, and water reuse in Kuwait. It focused on three municipal wastewater treatment plants (WWTPs) with different design capacities, namely Sulaibiya (600,000 m3/d), Kabd (180,000 m3/d), and Umm Al-Hayman (27,000 m3/d), all using tertiary treatment. Daily data records were obtained on influent and effluent over the years 2018–2020 (before and during the pandemic). In addition, influent and effluent samples were collected from the Sulaibiya and Kabd plants for laboratory analysis to determine the effect of increase in the use of home disinfectants. The results indicate an increase (<50%) in the average daily flow rates received in WWTPs during the 2020 home quarantine lockdowns. Statistical analysis showed stability of the Sulaibiya in BOD5, COD, and TSS removal efficiency while a decrease in the Kabd and UAH plants removal efficiency was observed during the pandemic. During the lockdown period, GC-MS analysis showed a high probability of chloroxylenol (>90), one of the main components of Dettol disinfectant, existing in the raw wastewater samples while the GC-FID analysis indicated the presence of (PAH) as emerging contaminants, at higher concentrations in the influent and effluent samples. The pandemic adversely affected wastewater treatment plant performance and excessive use of Dettol disinfectant by homes resulted in the presence of objectionable organic pollutants in the tertiary-treated effluent which would impair water reuse. Reverse osmosis process used in Sulaibiya plant proved to be effective in removing residual organics and improving effluent quality for reuse during the pandemic.

Wastewater treatment allows for the safe disposal of municipal and industrial wastewater to protect public health and the ecosystem[...]

Water and wastewater treatment plant operators must have a breadth of knowledge that encompasses more than scientific theory. They need to be generalists with knowledge bridging several scientific, academic, and engineering disciplines. Unfortunately, until now, many of the existing texts in the field were too limited in scope and narrow in focus.

Ensuring the stable operation of urban wastewater treatment plants (WWTPs) and achieving energy conservation and emission reduction have become serious problems with the improvement of national requirements for WWTP effluent. Based on a wastewater quality analysis, identification of the contaminant removal, and a simulation and optimization of the wastewater treatment process, a practical engineering diagnosis method for the cyclic activated sludge technology process of WWTPs in China and an optimal control scheme are proposed in this study. Results showed that exceeding the standard of effluent nitrogen and phosphorus due to unreasonable process cycle setting and insufficient influent carbon source is dangerous. The total nitrogen removal rate increased by 9.5% and steadily increased to 67% when agitation was added to the first 40 min of the cycle. Additionally, the total phosphorus (TP) was reduced to 0.27 mg/L after replacing the phosphorus removal agent polyferric sulfate with polyaluminum iron. The corresponding increase in the TP removal rate to 97% resulted in a reduction in the treatment cost by 0.008 CNY/t.

Sludge management is a very relevant aspect in the operation of Wastewater Treatment Plants (WWTPs). In activated sludge systems, it is common to have daily (or continuous) monitoring of total suspended solids in the aeration tank (MLSS). If such control is not properly performed, it can cause solids to wash out in the secondary sedimentation tank or significantly impact BOD (Biochemical Oxygen Demand) and nitrogen removal. There are many commercially available systems which can provide real-time monitoring of solids (mainly optical or ultrasound sensors). Even though commercially available (usually with a high cost), there are still issues related to the use of such sensors. The most important one is the progressive accumulation of solids, which cause measurement errors. In this work, the authors investigated the application of a low-cost US sensor for MLSS (mixed-liquor suspended solids) monitoring in two full-scale activated sludge WWTPs. The tested sensor was similar to a previously described device, which had been previously employed in a pilot-scale UASB reactor in Brazil. The main differences were related to an integrated treatment and acquisition system which allowed real-time treatment of the US wave as well as data acquisition at a predefined time. The values generated by the sensor were compared with a commercial optical sensor installed in the same WWTP and double-checked with periodic gravimetric tests. The results at a Leeuwarden WWTP showed that the measurements of the US sensor, the optical sensor, and gravimetric test did not present significant differences during the test period at a significance level of 5%. Absolute errors were on average 0.04% (US sensor) and 0.03% (optic sensor) of MLSS compared to the gravimetric test. Although the use of the tested US sensor for monitoring solids in WWTP is promising, there are still several improvements that need to be made to the sensor. These include implementing a more precise calibration frequency, establishing a cleaning routine, and preventing sensor fouling. Furthermore, the sensor still needs a more thorough cost–benefit analysis, which would help assess the practicality of implementing this technology in various WWTPs.

The operation of modern wastewater treatment plants (WWTPs) is driven by activated sludge microbiota, a complex assemblage of trophically interacting microorganisms. Microbial predation is crucial to fundamental understanding of how biological interactions drive microbiome structuring and functioning of WWTPs. However, predatory bacteria have received little attention regarding their diversity, activity, and ecological function in activated sludge, limiting the exploitation of food web interactions for wastewater microbiome engineering. Here, by using rRNA-stable isotope probing of activated sludge microbiota with 13C-labeled prey bacteria, we uncovered diverse as-yet-uncultivated putative predatory bacteria that actively incorporated 13C-biomass. Myxobacteria, especially Haliangium and the mle1-27 clade, were found as the dominant active predators, refreshing conventional views based on a few predatory isolates of Bdellovibrionota from WWTPs. The identified predatory bacteria showed more selective predation on prey compared with the protists dominated by ciliates, providing in situ evidence for inter-domain predation behavior divergence in activated sludge. Putative predatory bacteria were tracked over a two-year microbiome monitoring effort at a local WWTP, revealing the predominance of Myxococcota (6.5 ± 1.3%) over Bdellovibrionota (1.0 ± 0.2%) lineages. Phylogenetic analysis unveiled highly diverse myxobacteria inhabiting activated sludge and suggested a habitat filtering effect in global WWTPs. Further mining of a global activated sludge microbiome dataset revealed the prevalence of Myxococcota (5.4 ± 0.1%) species and potential impacts of myxobacterial predation on process performance. Collectively, our findings provided unique insights into the predating activity, diversity, and prevalence of Myxococcota species in activated sludge, highlighting their links with wastewater treatment processes via trophic regulation of enteric and functional bacteria.

Prediction of effluent quality in a wastewater treatment plant by dynamic neural network modeling

Chapter 9 - Wastewater Treatment