Sanitary sewage

The treatment and disposal of domestic sewage is one of Brazil's main challenges. Sewage composition varies with the habits of the population and the frequency with which new contaminants are released into the environment. This study is a bibliographical review of the main aspects related to the characterization and composition of sanitary sewage, types of sewage treatment systems and pertinent legislation; and toxicity of domestic effluents. The review was based on publications available on Science Direct, Google Scholar and Scielo, as well as on printed publications, relevant legislation, and normative instructions. The research period adopted for the selection of publications was from 2005 to 2021. We found out that, in addition to the levels of organic matter from domestic sewage, residues from products used in daily life, such as pharmaceuticals and cleaning products, can be found in effluents in concentrations harmful to the environment. Often, the types of treatment used in municipal sewage treatment plants do not efficiently remove these contaminants. Thus, even if sewage is treated to meet the limits required for the physical-chemical and biological parameters established by law, domestic effluent can present a high potential for toxicity to various aquatic species such as microcrustaceans, mollusks and fish. Thus, ecotoxicological analyses represent a remarkable mechanism for indicating the efficiency of removal of emerging contaminants present in treated sanitary effluent, in addition to indicating the deleterious effects caused by these residues to the environment and ecosystems associated with the receiving water body.

Effect of turbidity on ultraviolet disinfection of domestic wastewater for agricultural reuse

Water treatment and reuse are fundamental because of the increasing demand for freshwater, especially in agriculture. Accordingly, this study evaluated the effects of turbidity of wastewater processed at the Effluent Treatment Station (ETE) of the UFSCar/Araras and of UV dose on microbial inactivation. The ETE treats up to 2000 L of wastewater daily from toilets and a university restaurant and has five components (grease box, septic tank, microalgae tank, upflow anaerobic filter, and wetlands). Pretreated effluents were used in the experiments, and sampling sites consisted of inspection boxes located after the wetlands. Sample collection, inspection, preservation, and analyses were performed according to standard methods. Sample turbidity was adjusted to 5, 50, 100, 200, and 300 nephelometric turbidity units (NTU), and UV doses of 7.2–28.8 mWs cm-2 were used. A 5 x 5 factorial design (five turbidity levels and five radiation doses) was used, totaling 25 treatments. Each treatment was performed in triplicate. The data were submitted to analysis of variance and Tukey’s test. The results showed that the increase in turbidity significantly decreased disinfection efficiency in samples with turbidity levels higher than 50 NTU. The microbial inactivation coefficients obtained here can be extrapolated to disinfection of wastewater with turbidity up to 300 NTU to eliminate thermotolerant coliforms. The UV sterilizer is feasible for wastewater treatment and its reuse in agriculture. Keywords: domestic effluent, sustainability, ultraviolet radiation, water reuse.

Distribution of Geochemical Species of P, Fe and Mn in Surface Sediments in the Eutrophic Estuary, Northern Taiwan

The Danshuei River Estuary (DRE) in northern Taiwan is a seriously eutrophic estuary due to the domestic effluent discharge. Surface sediment samples were collected from the DRE to study the concentrations and spatial distributions of different fractions of phosphorus through the five-step sequential extraction method which chemically divides the sedimentary P into five fractions: PSORB, PCDB, PCFA, PDET, and PORG. The Fe and Mn contents in the extracted solution were also determined. The total organic carbon (TOC) and grain size in sediment samples were analyzed as well. The sedimentary total P (TP) concentrations ranged within 537–1310 mg/kg and mostly exceeded 800 mg/kg, suggesting that the DRE sediments were moderately polluted by phosphorus. The PCDB was the dominant fraction of P, averagely contributing 58% of TP, followed by PDET 31%. The contributions of the PSORB and PCFA fractions to the TP were relatively minor. Two fractions, FeCDB and FeORG, of sedimentary Fe equally shared approximately 70% of total Fe, followed by FeDET with 22%. The contribution of different fractions of sedimentary Mn followed the sequence: MnCDB (36%) > MnCFA (29%) > MnORG (14.7%) > MnDET (14.5%) > MnSORB (5.3%). The sedimentary P, Fe, and Mn within the DRE are easily mobilized because they were mainly present in the reducible fraction. The concentrations of sedimentary TP positively correlated with the TOC contents and inversely negatively correlated with grain size, suggesting that the TOC and grain size play the crucial roles in influencing the distribution of sedimentary P within the DRE. Finally, the Fe(III) (hydro)oxides seems to play an important carriers to adsorb dissolved P because PCDB positively correlated with FeCDB.

Performance evaluation and coefficients of reliability for waste stabilization ponds in northeast Brazil

This paper assesses the reliability of Waste Stabilization Ponds (WSP) and proposes an alternative approach to WSP design based on the calculation of coefficient of reliability (COR) from an acceptable measure of violation of discharge standards. For that, data were collected from 10 full-scale systems operating in Northeast Brazil. All systems receive predominantly domestic effluent and are composed of one facultative pond and two serial maturation ponds. Different levels of restriction for effluent discharge were considered regarding the parameters: BOD, COD, total suspended solids, ammonia and thermotolerant coliforms. The Log-normal Probability Distribution Function (PDF) was able to represent the behavior of the concentration data in the effluent and, therefore, allowed the COR calculation. The COR was obtained from the coefficient of variation (CV) of the concentrations and the standardized normal variable associated with a 95% probability of non-exceedance. The observed dispersion of the results proved to be detrimental to the adoption of a single COR value for the evaluated parameters. In addition, the comparison between observed and design/operational concentration for optimal performance showed that the 95% reliability scenario represents a less achievable target for WSP systems.

Effects of domestic effluent utilisation on the blood characteristics of grower pullets

Two hundred 10- weeks old golden Hubbard grower chickens were randomly assigned to four water treatments: tap water (TW), alum treated domestic sewage (ATDS), secondary treatment domestic sewage (STDS) and raw domestic sewage (RDS). Each treatment was replicated twice with 25 birds per replicate. The trial lasted for 9 weeks. The experimental waters were analysed to determine their quality, water consumption by the chickens in each treatment was measured to assess their acceptability and the effects of water treatments on hematological and serum biochemical constituents over time were evaluated. The sequence of water quality in decreasing order is TW, ATDS, STDS and RDS. The effect of the water treatments on water consumption of the chickens was not significant (p>0.05). The packed cell volune, haemoglobin, serum total protein, serum albumin, serum globulin, serum calcium and serum phosphorus of the birds were not significantly different (p>0.05) at each bleeding throughout the experiment. While the blood constituents evaluated all had values within the normal limits, the concentrations of calcium in the sera of the bird receiving AIDS were slightly lower at weeks 5 and 9. The chickens on any of the treatments suffered no apparent harm. The physiological constitution of the chickens at this stage of growth appears to be able to accommodate the differences in the chemical and physical compositions of the domestic sewage effluents without disrupting the animal health.

An optimal control problem applied to a wastewater treatment plant

<p style='text-indent:20px;'>This paper aims to present a mathematical model that describes the operation of an activated sludge system during one day. Such system is used in the majority of wastewater treatment plants and depends strongly on the dissolved oxygen, since it is a biological treatment. To guarantee the appropriate amount of dissolved oxygen, expensive aeration strategies are demanded, leading to high costs in terms of energy consumption. It was considered a typical domestic effluent as the wastewater to test the mathematical model and it was used the ASM1 to describe the activated sludge behaviour. An optimal control problem was formulated whose cost functional considers the trade-off between the minimization of the control variable herein considered (the dissolved oxygen) and the quality index that is the amount of pollution. The optimal control problem is treated as a nonlinear optimization problem after discretization by direct methods. The problem was then coded in the AMPL programming language in order to carry out numerical simulations using the NLP solver IPOPT from NEOS Server.</p>