Biological Sewage Treatment Plant Research Articles

Assessment of Cu(II) impact on aerobic sludge biomass and its post-exposure self-recovery potential

Heavy metals are released from various sources, including metal plating, potentially at a small-scale industrial level, and from automobile service and repair workshops, paint works, etc., spread across the city. Being part and parcel of the city, the wastewater from these metallic sources finds its way into the sewage system and can potentially disrupt biological sewage treatment plants. Therefore, conducting health and quality assessments of the sludge biomass becomes crucial to ensure the effective operation of these treatment plants and to maintain environmental and public health standards. In this study, impacts of Cu(II) (10, 20, 40, and 80 mg/L) exposure on sludge biomass have been investigated, and the potential of self-recovery of sludge biomass was explored when Cu(II) exposure is stopped. Reactors have been operated for 0–25 d with Cu(II) (termed as stressed phase) and then another 29 d without Cu(II) (termed as recovery phase) in the feed. During stressed phase operation, Cu(II) stressed reactors have shown 39–75 % chemical oxygen demand (COD) removal, compared to 91 % for control. Biomass activity and ECatalase activity have been inhibited under Cu(II) stress with changes in microbial community structure. During the recovery phase, Cu(II) stressed reactors have shown 41–82 % COD removal, whereas the control reactor has shown 91 % COD removal. A low sludge volume index (SVI) and high biomass interface settling velocity (ISV) with increased biomass activity have been obtained for biomass exposed to 10 and 20 mg/L of Cu(II). Lower Cu(II) doses have led to partial recovery of enzyme activity and microbial community structure, but higher doses have shown incomplete recovery. The study shows the impact caused by Cu(II) metal in a biological wastewater treatment reactor. Through comprehensive analysis of basic and advanced physico-chemical and biological parameters, the study recommends preliminary and confirmatory tests to know metallic ingress through wastewater influent in a treatment system. Advanced knowledge about metallic ingress will be useful for operators to take necessary steps for the sustainable operation of wastewater treatment systems.

Hierarchically porous biochar derived from aerobic granular sludge for high-performance membrane capacitive deionization

Membrane capacitive deionization (MCDI) is a cost-effective desalination technique known for its low energy consumption. The performance of MCDI cells relies on the properties of electrode materials. Activated carbon is the most widely used electrode material. However, the capacitive carbon available on the market is often expensive. Here, we developed hierarchically porous biochar by combining carbonization and activation processes, using easily acquired aerobic granular sludge (AGS) from biological sewage treatment plants as a precursor. The biochar had a specific surface area of 1822.07 m2 g−1, with a micropore area ratio of 58.65% and a micropore volume of 0.576 cm3 g−1. The MCDI cell employing the biochar as electrodes demonstrated a specific adsorption capacity of 34.35 mg g−1, comparable to commercially available activated carbon electrodes. Our study presents a green and sustainable approach for preparing highly efficient, hierarchically porous biochar from AGS, offering great potential for enhanced performance in MCDI applications.

Application of New Polymer Flocculants in Industrial Wastewater Treatment

Polymer flocculants are used in wastewater treatment processes, and the necessity and universality of their use result from changes in production technologies, also causing variability in the parameters of treated wastewater. Industrial wastewater contains a substrate that is difficult to biodegrade (BOD5/COD < 0.02), and the presence of toxic compounds makes it necessary to treat them in many stages before discharging them to the receiver or reusing. The study aimed to assess the possibility of using a new generation flocculent to support coagulation. The research was conducted on mine water originating from hard coal mines and on treated coke wastewater from the biological sewage treatment plant. The synthesis of copolymers of acrylamide with acrylic acid and acrylamide with acrylonitrile allowed the extraction of effective products – flocculents with specific properties, supporting the coagulation process and reducing the parameters of contaminants in treated industrial wastewater. Compared to commercial polyelectrolyte Praestol, copolymers of acrylamide with acrylic acid removed turbidity more effectively than acrylamide-acrylonitrile copolymers.

A new environment-friendly polyferric sulfate-catalyzed ozonation process for sludge conditioning to achieve deep dewatering and simultaneous detoxification

The dewaterability of sludge from biological sewage treatment plants is extremely poor since the highly hydrophilic biomacromolecules. This work developed a new polyferric sulfate-catalyzed ozonation (PFS/O 3 ) process to disintegrate sludge flocks and extracellular hydrophilic substrates for liberating bound water. With 40 mg/gTS PFS catalyzing 60 mg/gTS O 3 , bound water content declined to 1.42 g/gTS, and water content of dewatered sludge dropped to 59.79%. Meanwhile, microbial cells were inactivated by 47.3%, and extracellular protein-like components were degraded substantially, rendering the neutral potential and low apparent viscosity. PFS/O 3 treatment significant facilitated CHO-compound decomposition, reactions of nitrogenous groups, and P-containing biomolecule release. And more hydrophobic groups were exposed on the bio-matrix surface. Besides, polyhydroxy Fe as skeleton builder reconstructed sludge drainage passages for more water permeation. The predominant mechanism for enhancing sludge dewaterability in PFS/O 3 process was the oxidation role of improved • OH, and the chemical reaction chains were proposed tentatively. Moreover, this process simultaneously removed 26.95%–60.05% heavy metals and 31.18%–80.91% polycyclic aromatic hydrocarbons in dewatered sludge, and its chemical cost was preliminarily estimated as 88.80 USD$/tonTS. Therefore, the PFS/O 3 process was of great prospect and practical value in sludge treatment for dewatering and detoxification. • A new PFS-catalyzed O 3 process assisted sludge deep dewatering and detoxification. • EPS conformation turned to be loosened with more hydrophobic groups exposed. • Molecular composition and transformation of DOM were shown by ESI FT-ICR MS. • Chemical reaction mechanism of PFS-catalyzed O 3 was put forward for the first time. • Polyhydroxy Fe serving as supporting skeleton rebuilt multihole drainage passages.

Multiresidue Determination of Endocrine Disrupting Compounds in Sewage Treatment Plants (SPE-HPLC-DAD)

This work focuses on the validation and application of solid phase extraction followed by high-performance liquid chromatography (SPE-HPLC) analysis of important endocrine disruptors compounds (EDC) from different classes in highly complex wastewater matrix. The endocrine disruptors investigated included three different categories: pharmaceuticals (sulfamethoxazole (SMZ), trimethoprim (TMP) and diclofenac (DCF)), hormones (estrone (E1), 17α-ethinylestradiol (EE2) and 17β-estradiol (E2)) and plastic materials (bisphenol A (BPA)). The method involves pre-concentration by SPE using Strata-X extraction cartridges followed by HPLC coupled with diode array detector (DAD). As the assumption of homoscedasticity was met for analytical data, ordinary linear regression procedure was applied to the data. The method was considered validated for 7 EDC after consistent evaluation of the key analytical parameters. Recoveries were ranged from 52.3 to 179.6%. Limits of quantification were in the range 6.0-0.4 µg L−1. The described method was applied to evaluate the occurrence and removal efficiency of EDC in two biological sewage treatment plants (STPs). The influent mean concentrations of E1, E2 and EE2 hormones were 79.54; 175.09 and 102.19 µg L−1, respectively, while for SMZ, TMP, DCF and BPA were 215.17; 187.01; 218.97 and 87.12 µg L−1 for STP A, respectively. The efficiencies for the removal of EDCs ranged from 0 to 79.4%.

Quantitative estimation of wastewater quality parameters by hyperspectral band screening using GC, VIP and SPA.

Water pollution has been hindering the world’s sustainable development. The accurate inversion of water quality parameters in sewage with visible-near infrared spectroscopy can improve the effectiveness and rational utilization and management of water resources. However, the accuracy of spectral models of water quality parameters is usually prone to noise information and high dimensionality of spectral data. This study aimed to enhance the model accuracy through optimizing the spectral models based on the sensitive spectral intervals of different water quality parameters. To this end, six kinds of sewage water taken from a biological sewage treatment plant went through laboratory physical and chemical tests. In total, 87 samples of sewage water were obtained by adding different amount of pure water to them. The raw reflectance (Rraw) of the samples were collected with analytical spectral devices. The Rraw-SNV were obtained from the Rraw processed with the standard normal variable. Then, the sensitive spectral intervals of each of the six water quality parameters, namely, chemical oxygen demand (COD), biological oxygen demand (BOD), NH3-N, the total dissolved substances (TDS), total hardness (TH) and total alkalinity (TA), were selected using three different methods: gray correlation (GC), variable importance in projection (VIP) and set pair analysis (SPA). Finally, the performance of both extreme learning machine (ELM) and partial least squares regression (PLSR) was investigated based on the sensitive spectral intervals. The results demonstrated that the model accuracy based on the sensitive spectral ranges screened through different methods appeared different. The GC method had better performance in reducing the redundancy and the VIP method was better in information preservation. The SPA method could make the optimal trade-offs between information preservation and redundancy reduction and it could retain maximal spectral band intervals with good response to the inversion parameters. The accuracy of the models based on varied sensitive spectral ranges selected by the three analysis methods was different: the GC was the highest, the SPA came next and the VIP was the lowest. On the whole, PLSR and ELM both achieved satisfying model accuracy, but the prediction accuracy of the latter was higher than the former. Great differences existed among the optimal inversion accuracy of different water quality parameters: COD, BOD and TN were very high; TA relatively high; and TDS and TH relatively low. These findings can provide a new way to optimize the spectral model of wastewater biochemical parameters and thus improve its prediction precision.

ALGORITHM OF MANAGEMENT OF WATER-PROTECTIVE ACTIVITY OF JSC «SEGEZHA PPM» ON BASIS OF MATHEMATICAL MODELING

Modern environmental legislation of the Russian Federation requires the introduction of automated systems for the control of waste and natural waters for large water users, which include JSC «Segezha PPM». The article proposes an algorithm for integrating the current automated process control system of JSC «Segezha PPM» into a unified system of water safety management. The proposed automated control system contains sensors for monitoring the parameters of the production process, the parameters of biological sewage treatment plants, wastewater and Lake Vygozer in the background section. The process of managing water protection activities is based on the use of neural networks, an event tree, and models of convective-diffusive transfer and transformation of substances in water bodies. The implementation of the system will ensure the environmental quality standards of the water body, optimally redistribute the load between water outlets, optimize the parameters of the production process, and form model forecasts of the state of Lake Vygozero.

ECOLOGICAL AND MICROBIOLOGICAL ASSESSMENT OF SEWAGE SLUDGE OF WASTE TREATMENT PLANTS IN THE CITY OF ODESA

Objective. Investigate the number of microorganisms – representatives of various ecological trophic groups in mechanically dewatered and naturally disinfected sewage sludge (SS) of the biological sewage treatment plants (BSTP) “Pivnichna” and “Pivdenna” of the City of Odesa to determine their suitability for microbiological parameters for use as fertilizers in agriculture.
 Methods. Microbiological, statistical.
 Results. It was established that SS of BSTP “Pivdenna” and “Pivnichna” in the City of Odesa, bacteria that consume organic and mineral nitrogen compounds, phosphate-mobilizing microorganisms, are actively developing, due to the presence of the corresponding trophic substrates. By the number of ammonifiers, microorganisms that consume mineral compounds of phosphorus and bacteria capable of hydrolyzing the organophosphates, spore microorganisms, the waste is inferior to traditional organic manure – animal manure. The functional orientation of microbiological processes in the studied substrates is determined on the basis of the obtained data, calculations of the mineralization-immobilization factors and the oligotrophic index. The parameters of the mineralization-immobilization factors (0.04-0.2) in the SS indicate the predominance of synthesis processes over the destruction of organic matter. The oligotrophic index (an indicator of the supply of substrates with easily digestible nutrients) shows insignificant content of nutrients available for microorganisms in SS from BSTP “Pivnichna” (OI = 1.0) and a high level of supply with nutrients of SS from BSTP “Pivdenna” (OI = 0.1). In general, according to microbiological parameters, investigated SS are suitable for use as fertilizing substrates in agriculture.
 Conclusion. Taking into account the obtained data and taking into account the results of previous studies on the compliance of SS with sanitary regulations, it can be considered that the use of SS as fertilizers will have a positive effect on the functioning of agrocenoses.

Influence of Sitkówka sewage treatment plant on the Bobrza River water quality

Abstract The paper presents an analysis of 20 physicochemical elements in the Bobrza River water sampled above and below the treated sewage discharge point. Sitkówka mechanical and biological sewage treatment plant with a value of 289 000 People Equivalent discharges on average 51 000 m3 of treated sewage daily, which makes up 29% of mean daily flow in the Bobrza River. On the basis of hydrochemical analyses it was stated that the discharge of treated sewage led to worsening of 18 out of 20 studied water quality indices in the Bobrza River. In the river water below the sewage discharge statistically significantly higher values of electrolytic conductivity, dissolved solids, calcium, magnesium, sodium and potassium were registered. A decrease in dissolved oxygen content in the water and increase in its electrolytic conductivity caused a change of water quality class in the Bobrza River from the maximum potential to potential below good. On the other hand, increase in concentrations of dissolved solids and sulphates caused a change of the water class from the maximum potential to good potential. Statistical factor analysis (FA) made possible a reduction of a set of 20 physicochemical elements to four mutually orthogonal factors explaining 95% (above the treatment plant) and 96% (below the treatment plant) of the internal structure of primary data. The first factor is connected with point source pollution (sewage discharge), the second describes oxygen conditions in water, the third results from seasonality and is responsible for the pollutants from natural sources, whereas the fourth factor has not been unanimously defined yet.

HUMAN INTERFERENCES TO THE ENVIRONMENT, CONSEQUENCES AND CARE

The need to restore the relationship of mankind with the environment led to the designation of measures, terms and processes worldwide for the prevention or reduction to the highest possible degree of the negative consequences to the environment ensuring a high level of protection of human health and the environment. It is general ascertainment that there is a big lack of objective information in Greece regarding the possibilities of modern science and technology for the treatment of Solid Industrial Wastes (SIW), Municipal Solid Wastes (MSW) and biological Sewage Treatment Plants (STP) products safely for the public health and the environment. In Greece the most significant sources of SIW are the big exploitations of “Mineral Ores”.On the contrary, the cement industries provide an important way out for the consumption of SIW like fly ash, red mud, et. A big percentage of the total amount of produced alloys of iron, copper, zinc and aluminium do not use “Mineral Resources” as raw materials but recycle scrap metals. At the end, the successful results of pyrometallurgical production of final products by SIW as well as the results of the production of new friendly to the environment and high technology refractory materials are given in this work.

Detection and genotyping of group A rotaviruses isolated from sewage samples in Monastir, Tunisia between April 2007 and April 2010.

To ascertain the viral load, the distribution of G and P types of group A rotaviruses (RV-A) in sewage samples and to compare strains in clinical, animal and environmental samples. During our study from April 2007 to April 2010, 518 samples of raw and treated sewage were collected from two biological sewage treatment plants (STPs) located in the Monastir region, Tunisia. RV-A was detected by real-time RT-PCR in 375 (72·4%) sewage samples. According to the quantification results of RV-A, it appears that the viral load in raw and treated sewage of the two STPs was quite similar (P=0·735). The genotyping of RV-A strains detected in sewage samples showed a great diversity with 10G types and 8 P types. Most of them were described as common in humans, but we also detected genotypes commonly found in animals. All the genotypes detected in two previous studies performed in our laboratory on clinical and bovine samples were also found in environmental samples. However, some genotypes commonly found in animal were only found in sewage samples. The comparison of environmental, clinical and animal data suggests that STPs may convey not only human sewage but also animal wastes, both of them contaminated with numerous RV-A strains which are not efficiently eliminated by the sewage treatment process and may spread to surface waters. This work demonstrates the potential release of human and animal RV-A into water sources, representing a public health risk, by inducing gastroenteritis in population, but also by increasing the risk of zoonotic transmission and formation of reassortant viruses which could get a higher infectious potential. Our findings also suggest that monitoring of sewage may provide an additional tool to determine the epidemiology of RV-A circulating in a given community.

Molecular detection of human noroviruses in influent and effluent samples from two biological sewage treatment plants in the region of Monastir, Tunisia.

Noroviruses (NoVs) are responsible for numerous cases of waterborne and foodborne gastroenteritis every year. They are released in the sewage and their detection in this environment can reflect the epidemiology of the viral strains circulating in the community. A three-year (2007-2010) survey was conducted in order to evaluate the presence of human NoVs using RT-PCR in 518 sewage samples collected at the entrance and exit of two biological sewage treatment plants located in Monastir region, Tunisia. In this study, we aimed to genetically characterize the most prevalent GI and GII NoV strains, in order to obtain a rough estimate of the efficacy of disinfection treatments and to compare the results with clinical data documented in the same area during the same period. This work confirms the wide circulation and the genetic diversity of NoVs in Tunisia and the widespread distribution of NoV variants in both raw and treated wastewater. Indeed, NoV was detected in 192 (37.1%) sewage samples, among them mixed infections with group A rotavirus were detected in 125 (65.1%) cases. The genotypes of the GI NoVs were GI.1, GI.2, GI.4, GI.5, and GI of unassigned genotype (GI.UA), and the genotypes of the GII NoVs were all GII.12. This study enhances the currently poor environmental virological data gathered in Tunisia, demonstrates the benefit of environmental surveillance as a tool to determine the epidemiology of NoVs circulating in a given community, and underlines the need for the design and support of similar long-term studies in our country, in order to compensate for the absence of a national surveillance system for gastroenteric viruses.

Simultaneous Spectrophotometric Determination of Orthophosphate and Silicate Ions in River Water Using Ion-Exclusion Chromatography with an Ascorbate Solution as Both Eluent and Reducing Agent, Followed by Postcolumn Derivatization with Molybdate

Ion-exclusion chromatography was examined for the simultaneous spectrophotometric determinations of orthophosphate and silicate ions in river water using an ascorbate solution as both an eluent and a reducing agent, followed by postcolumn derivatization using molybdate. The detector responses for both ions increased with increased ascorbic acid concentration in the eluent, but peak tailing was observed for the orthophosphate ion. This suggests that the amounts of undissociated orthophosphate ions increased with decreased eluent pH, resulting in the penetration of the phosphate to the Donnan's membrane formed on the resin surface. Using a neutral sodium ascorbate solution as an eluent, the peak shape was improved. With optimized separation and derivatization conditions (eluent, 20 mM sodium ascorbate; color-forming reagent, 10 mM sodium molybdate-60 mM sulfuric acid; flow rates of eluent and color-forming reagent, 0.4 and 0.2 mL min(-1); coil length, 6 m), the detection limits of orthophosphate and silicate ions were 0.9 and 1.0 microg L(-1), respectively. This method was successfully applied to the determination of orthophosphate and silicate ions in Kurose River water and the quantitative evaluations of the effects of water intake to a reservoir and discharge from a biological sewage treatment plant on the fluxes of these ions in the river.

Discharge of pharmaceutical products (PPs) through a conventional biological sewage treatment plant: MECs vs PECs?

Pharmaceuticals for human use are consumed in significant quantities and their occurrence in aquatic systems has been reported by a number of authors. In the context of environmental risk assessment, there is an increasing interest in evaluating the discharge of pharmaceutical products to surface waters through sewage treatment plants (STP). This case study was carried out on a conventional biological treatment plant (Alès, France) and focused on a set of eleven drugs representing the main therapeutic classes. Measured environmental concentrations (MECs) range from the low ng L − 1 to 1.5 µg L − 1 in effluent and up to few hundred ng L − 1 in receiving surface waters. There is a good agreement between MEC and predicted environmental concentration (PEC) values for seven of the eleven investigated drugs in STP effluent. There is not such a good match between PEC and MEC values in surface waters, and this highlights the limits of this approach, at the local scale.

Simultaneous spectrophotometric determination of phosphate and silicate ions in river water by using ion-exclusion chromatographic separation and post-column derivatization

The simultaneous spectrophotometric determination of phosphate and silicate ions in river water was examined by using ion-exclusion chromatography and post-column derivatization. Phosphate and silicate ions were separated by the ion-exclusion column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the H +-form (TSKgel Super IC-A/C) by using ultra pure water as an eluent. After the post-column derivatization with molybdate and ascorbic acid, so-called molybdenum-blue, both ions were determined simultaneously by spectrophotometry. The effects of sulfuric acid, sodium molybdate and ascorbic acid concentrations and reaction coil length, which have relation to form the reduced complexes of molybdate and ions, on the detector response for phosphate and silicate ions were investigated. Under the optimized conditions (color-forming reactant, 50 mM sulfuric acid–10 mM sodium molybdate; reducing agent, 50 mM ascorbic acid; reaction coil length, 6 m), the calibration curves of phosphate and silicate ions were linear in the range of 50–2000 μg L −1 as P and 250–10,000 μg L −1 as Si. This method was successfully applied to water quality monitoring of Kurose-river watershed and it suggested that the effluent from a biological sewage treatment plant was significant source of phosphate ion in Kurose-river water.

Phosphate Elimination and Recovery From by Active Filtration Using Crushed Gas Concrete

Laboratory long-term upstream fixed-bed experiments were carried out to investigate the efficiency of phosphorus elimination with the effluent of a biological sewage treatment plant using crushed gas concrete. The development of the pHvalue in the column outflow as well as the reaction kinetics was investigated. Furthermore, the phosphorus yield was balanced for phosphorus recovery and the calcium phosphate compounds generated were specified by mineralogical analysis methods. These activities were followed by a study with respect to the suitability of the material as raw material for the phosphate industry.

The effect of a new sewage treatment plant on faecal indicator numbers, campylobacters and bathing water compliance in Morecambe Bay.

Until recently, sewage from Morecambe was macerated, but otherwise untreated, and discharged at high water via a short outfall pipe into Morecambe Bay adjacent to a recognized bathing water. In March 1997, a new biological sewage treatment plant came on-line and the effluent was discharged via a longer outfall pipe into the Bay south of Heysham. The effect of the new sewage treatment on the quality of the bathing waters was monitored by testing sea water collected from the three EU designated bathing waters on Morecambe Bay: Morecambe North, Morecambe South and Heysham. After sewage treatment came on-line, the numbers of faecal coliforms and faecal streptococci were lower at Morecambe North and Morecambe South but higher at Heysham. Although the changes in numbers were not always statistically significant, they were sufficient to affect compliance with the EU Bathing Water Directive Imperative (mandatory) standards. Compliance improved markedly at Morecambe North and South but declined at Heysham, the closest bathing site to the new outfall. Numbers of thermophilic campylobacters were similar in both years, which is suggestive of their sources being different from those of the indicator bacteria. Campylobacter lari and urease-positive thermophilic campylobacters (UPTC) were the only species of Campylobacter isolated from Morecambe's bathing waters. Very low numbers of Salmonella were found, with Salm, arizonae the only species isolated.

Behavior of fluorescent whitening agents during sewage treatment

Fluorescent whitening agents (FWAs) are contained in most modern laundry detergents and are thus discharged in substantial quantities with household wastewater. To determine the mass flows and fate of the predominant detergent FWAs, a field study was conducted at a full-scale mechanical–biological sewage treatment plant at Zürich-Glatt, Switzerland. Samples of wastewater (raw sewage, and primary and secondary effluent) and sludge (raw, activated, and anaerobically-digested sludge) were collected during a 10-day period. The concentration of FWAs in water samples was determined using solid-phase extraction with C 18 disks and high-performance liquid chromatography (HPLC). The concentration of FWAs in sludge was determined by supercritical fluid extraction and HPLC. The removal of FWAs from wastewater during sewage treatment varied significantly (53–98%) between different FWAs. Removal was due to adsorption to primary and activated sludge and the observed extent of removal was consistent with the individual sorption behavior of FWAs. No evidence for biodegradation of FWAs was found during the aerobic biological treatment of municipal wastewater with activated sludge and during anaerobic–mesophilic digestion of sewage sludge. Average annual discharge of FWAs to Swiss surface water is approximately 20 t (22% of the consumed FWAs) while FWA disposal to farmland associated with sewage sludge is 11 t/y (12%), estimated based on the extent of removal from sewage and on a previously reported survey of FWA concentrations in sewage sludge. The discharge of FWAs to surface water leads to a projected average FWA concentration in surface waters of 0.5 μg/l, which is well below toxic levels for these compounds.

Determination of polycyclic aromatic compounds and heavy metals in sludges from biological sewage treatment plants

The procedure of the analysis of polycyclic aromatic hydrocarbons (PAHs) and their derivatives in the sludges from biological sewage treatment plants has been worked out. The analysis included isolation of organic matter from sludges, separation of the extract into fractions of similar chemical character, qualitative–quantitative analysis of individual PAHs and their nitrogenated and oxygenated derivatives. Liquid–solid chromatography, solid-phase extraction and semipreparative band thin-layer chromatography techniques were used for the separation. Capillary gas chromatography–mass spectrometry analysis of the separated fractions enabled identification of more than 21 PAHs, including hydrocarbons which contained 2-6 aromatic rings as well as their alkyl derivatives, 10 oxygen derivatives, 9 nitroarenes, aminoarenes and over 20 azaarenes and carbazoles. Using the capillary gas chromatography–flame ionization detection technique the content of 17 dominant PAHs was determined. The content of heavy metals was determined in investigated sludges with the use of atomic absorption spectrometry. The concentrations of the respective metals could be ranked in the order Cd<Co<Ni<Pb<Cr≤Cu<Mn<Zn<Fe. The sludges were analysed for the first time in Poland in view of their possible utilisation in agriculture and in cultivating dumps of coal mine wastes, taking into consideration the contents of toxic organic pollutants and heavy metals.

CHEMICAL TREATMENT OF SEWAGE

Sewage treatment protects the receiving water from organic matter, nutrients, bacteria and viruses. The removal efficiency can be explained in terms of primary and secondary oxygen consumption. In Egypt the biological treatment process didn't prevent eutrophication in the receiving water bodies. Phosphorus is often the limiting factor for the algal growth. Today chemical precipitation is more frequently discussed as an alternative or complement to biological treatment. In many closed governorates,(Dakahlia, Damietta, El- Gharbia, El-Monofia, El-Kaliobia,... etc. ), the most crucial factor in erecting biological sewage treatment plants is the availability of land. In this paper the emphasizes will be on the demonstration of the different aspects of chemical sewage treatment as an alternative or complementary for biological sewage treatment, in addition to an experimental investigation for the use of conventional coagulants in sewage treatment through direct precipitation.