water Article
The Testing of Standard and Recyclable Filter Media to Eliminate Hydrogen Sulphide from Sewerage Systems Petr Hluštík 1, * and Jiˇrí Novotný 2 1 2
*
Institute of Municipal Water Management, Faculty of Civil Engineering, Brno University of Technology, AdMaS Centre, Purkynova ˇ 139, 612 00 Brno, Czech Republic Company Vodárenská akciová spoleˇcnost, a.s., Sobˇešická 820/156, 638 00 Brno, Czech Republic;
[email protected] Correspondence:
[email protected]; Tel.: +420-541-147-735
Received: 1 May 2018; Accepted: 23 May 2018; Published: 25 May 2018
Abstract: This article focuses on the subject of odours forming in sewage transfer chambers with displacement inlets, as well as the odours in their vicinity. It further covers the locations of odour formation, factors influencing the formation of hydrogen sulphide in wastewater, methods of removing hydrogen sulphide from wastewater, and laboratory testing of filtration media efficacy at various concentration levels of H2 S. The laboratory testing of filtration media efficacy is performed for products normally used by sewerage system operators guaranteeing the elimination of hydrogen sulphide (activated carbon, natural minerals and gels), recyclable materials (paper) and secondary raw materials in the field of waste management (biochar—the final product of microwave pyrolysis). Odour generated by sewerage systems is a secondary issue faced by all sewerage system operators, who sustain considerable expense in corrective measures to address this problem. The most economical and widespread measure used by those operators is hydrogen sulphide removal by filtration (filtration materials). Filtration media are installed in special cartridges under sewage covers in locations where the irritating odour is formed. These filtration cartridges, designed solely to eliminate odour from the surroundings, show various degrees of efficacy in removing H2 S. Keywords: hydrogen sulphide; odour removal; filtration media efficacy; sorption capacity
1. Introduction Odour is one of the organoleptic properties of wastewater, which differ in terms of smell sensitivity. The sewerage operator should prevent the formation of odours and try to emit as few odour components into the air as possible. The primary objective is to prevent the formation of odours, mainly by controlling and managing processes at the producer level, as well as in the sewerage system and wastewater treatment plant [1]. However, odour cannot often be reduced at the point of origin and it is, therefore, necessary to apply a secondary solution to prevent the spread of odour and its resulting hazardous substances. As a result of organic matter degradation by microorganisms under anaerobic conditions, odours are already formed during wastewater flow in the sewerage system. Another source of odorous substances is industrial wastewater connected to the public sewerage system. Wastewater components participating in the formation of odour [2,3] include sulphide (hydrogen sulphide), ammonia, organic sulphur compounds, thiols (e.g., mercaptans), amines (indole and skatole) and other organic compounds. The characteristic conditions for the formation of odour in the sewerage network can be defined as:
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in sewerage networks and house drains under adverse technical conditions; in transfer manholes with delivery pipe inlets; in long pressure pipes; in discharges of special industrial wastewater; in wastewater reuse by consumers and the resulting minimal flow rates in sewers; in sludge storage and sludge treatment facilities (sediments); improper operation and maintenance of both sewerage and facilities.
Elimination of odour from sewerage systems should be a high priority of operators. Odour causes nuisance to inhabitants living in the vicinity of the sewerage systems and has a direct impact on the service life of those sewers and machinery installed in sewerage facilities. In this case, the operator should perform a sensitivity analysis of the sewerage system and facilities, based on various combinations of variables, in order to assess the reliability of pipes and facilities using a software developed model [4,5]. European Union law defines “odour quality” in Directive 2008/50/EC of the European Parliament and of the Council on ambient air quality and cleaner air for Europe [6] for Europe and Directive 2010/75/EU of the European Parliament and of the Council on Industrial Emissions, Integrated Pollution Prevention and Control [7]. Sulphates (SO4 2− ) are converted by bacteria in municipal wastewater and through their metabolism into hydrogen sulphide. This process occurs predominantly in biofilms and sediments under anaerobic conditions in a submerged part of the sewer. The major reactions involving sulphur compounds in sewage are: 1. 2. 3. 4.
Reduction of sulphate to sulphide by sulphur-reducing bacteria. Decomposition of amino acids containing sulphur. Methylation of methyl mercaptan (CH3 SH) by H2 S [3,8]. Dimethyl sulphide (DMS) generation via oxidation of CH3 SH [9].
Hydrogen sulphide easily escapes from water, predominantly in areas of turbulent flows where water is spread into the surrounding air. Volatile hydrogen sulphide is heavier than the air and it accumulates in the free space inside the sewerage where it is slowly carried by the stream of wastewater in gravity sewers [10,11]. The main factors influencing the formation of odour in the sewerage are: 1.
2.
3.
Sewage composition: there is a significant influence of sulphide and sulphate concentrations in wastewater and special industrial service water [12]. Oxidation-reduction potential with values suited to anaerobic conditions: −50 mV. Temperature: biological oxygen demand increases with rising temperatures and anaerobic conditions are established in the sewerage system [13]. pH value: in more alkaline water there is a lower risk of hydrogen sulphide formation. Oxygen concentration: where values below 0.5 mg/L result in anaerobic conditions. Hydraulic factors: residence time, as longer residence times beyond 8 h result in anaerobic conditions in the sewerage system [12]. Poor technical design of the sewerage, where over-sizing results in low flow rates in the sewerage system, promoting sedimentation and the creation of an anaerobic environment. Velocity gradient, as a high velocity gradient causes considerable release of hydrogen sulphide into the air. Sediments and biofilm, where organic substrate is hydrolysed in anaerobic sediments along with fermentation, sulphate reduction and methane production [14]. Sewerage facilities and pumping stations, where long switching intervals of wastewater pumping result in an anaerobic environment. Pressurized sewers, causing long retention times in the pipeline and vacuum stations missing biofilters for exhaust air treatment.
Odour removal technologies can be divided into primary and secondary. The primary activity should be to prevent odour formation through controlled sewerage operations. In many cases,
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the operation cannot be controlled to avoid such formations. Thus, odour removal is a secondary activity and can be ensured either directly from wastewater or from the air. These activities cannot protect concrete pipelines against biogenic sulphuric corrosion. The hydrogen sulphide formed escapes through sewerage manholes to the surroundings and causes nuisance to the inhabitants, mostly in the summer months. Methods of removing odour from wastewater consist of chemical dosing into wastewater, which limits the formation of odour compounds. Such chemical dosing is carried out and recommended to be performed directly at the sewerage pumping stations. Methods used for the removal of odour from wasterwater are listed in Table 1. Table 1. Methods of removing odour from wastewater.
Iron salts precipitation
Iron can restrict the formation of sulphide in its divalent and trivalent forms. Divalent iron and sulphide form a black precipitate of ferrous sulphide. Trivalent iron can cause sulphate to be eliminated by producing elemental sulphur and oxidising to divalent iron. These iron salts used include ferrous chloride (FeCl2 ), ferrous sulphate heptahydrate (FeSO4 ·7H2 O) and iron chloride sulphate (FeClSO4 ) [15].
Chlorination
Chlorine is dosed into wastewater as a solution of gas that removes sulphide ions. The efficiency of sulphide reduction is limited due to the ability of chlorine to oxidise with organic and inorganic compounds. Adverse substances formed during the reaction of chlorine and certain organic substances with wastewater are trihalomethanes [16].
Oxidation by hydrogen peroxide
Hydrogen peroxide can oxidise sulphide to produce water and oxygen. In addition, by producing oxygen, hydrogen peroxide can contribute to maintaining aerobic conditions in wastewater and achieve high removal rates [17].
Oxidation using potassium permanganate
Potassium permanganate (KMnO4) is a strong agent that is capable of oxidising sulphide to sulphate. Typically, potassium permanganate is distributed in the dry state and it is therefore necessary to obtain an aqueous solution before application [18].
Biological oxidation of sulphide
The sulphide inhibition process also eliminates two types of bacteria—Thiomicrospira denitrificans and Thiobaciluus denitrificans. In the presence of nitrates, these bacteria are capable of oxidising sulphides and sulphur. Necessary electrons are taken from nitrates, which results in their reduction [19].
Restriction of anaerobic conditions using nitrate solution
Nitrate addition can establish anoxic conditions in wastewater. Nitrates are more easily reducible than sulphate in this environment, hereby reducing sulphide formation.
Compressed air or pure oxygen
Wastewater aeration is most often applied in pressure pipes or wet pits. Pure oxygen is five times more concentrated than oxygen contained in the air and, therefore, it is possible to achieve higher dissolved oxygen values in wastewater using oxygen 5 to 7 mg·L−1 than using air 3 to 5 mg·L−1 .
Secondary methods of removing odour from the air consist in the installation of an auxiliary system which, by means of physical, biological and chemical processes, captures hydrogen sulphide escaping into the environment. Methods used to eliminate odour from air are listed in Table 2.
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Table 2. Methods of removing odour from the air.
Air scrubber, oxidation and absorption
This technology can be used to treat practically all water-soluble contaminants. Liquid in the washer is sprinkled and creates artificial fog. The harmful substances are entrapped by the fog and dissolved from their gaseous phase into aqueous chemical solutions. The reaction mechanism is purely chemical and stable, resisting changes of input substances and external conditions [20].
Bio-air scrubbers
The bio-scrubber is fitted with an artificial carrier designed to have the largest possible surface area. Biofilm is then formed on the surface by sprinkled medium and substances separated from the air. There are two processes taking place in the biofilm, both physical and biochemical. As part of the physical process, gas molecules enter the sprinkled liquid and in the biochemical process the pollution is directly degraded in the liquid with the help of microorganisms [21,22].
Biological filters
This principle is similar to the bio-scrubber. The difference is that, instead of the biofilm medium, the filter medium is firm and the odorous substances are absorbed and degraded by microbiological organisms.
Biofilters with forced dry matter extraction
This biological filter technology can be used to treat various biodegradable water-soluble contaminants. Harmful substances from the air are dissolved in the filter from the gaseous to aqueous phase on the surface of an organic medium. For example, peat, tree bark, modified root and coconut fibres, as well as compost are used. Odour molecules are then degraded by the bacterial population in this medium [23].
Biofilters without forced dry matter extraction
Due to the absence of a ventilator and without the need for power supply for the ventilator, this type of filter can be directly fitted into the sewer manhole under the cover. The filter medium and its fraction must be selected so that the air can freely escape from the sewer without causing a significant pressure loss in the air flow [24].
Adsorption on filter material
When a filter material is used, the air flow passes through an adsorbent layer. The odour-causing compounds are attracted to the surface of the adsorbent. This is the simplest of the aforementioned odour-removal technologies. There is no need for any chemicals to be dosed into the system and there is no need to control biological processes that might be disturbed.
Photooxidation, ozonisation, ionization
To remove harmful substances from the air, ozone and hydroxyl ions are also used that are supplied into the air using strong electric discharges or short-wave ultraviolet (UV) radiation. This technology is preceded by a particulate filter so as not to damage UV lamps and electrodes.
Neutralization, compensation and masking
These methods only mask odours and the harmful substances lose their noticeable organoleptic properties. However, individuals are still in contact with dangerous substances and this makes it all the more dangerous because the odour loses its warning property. Essential oils and various natural and synthetic substances are used for this purpose. There are no chemical processes in contact with the air.
Fresh air dilution
Dilution of odorous substances is important in those cases where the operator wants to protect the pipeline from biogenic sulphide corrosion and it is possible to vent out large volumes of foul-smelling air into rural areas. The concentration of odorous substances in sewerage is significantly reduced by using a ventilator located in the pipeline.
The application of filtration media under the covers of the sewage chambers is the most widespread measure taken by operators of sewerage systems. Currently, the most common application uses standard filtration media on the basis of organic carbon, placed into special cartridges. Products offering filtration media used for sewage chambers worldwide are very widely used, with varied guaranteed effectiveness. So far, an overall independent effectiveness comparison of filtration media used has not been carried out.
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2. Materials and Methods Recycled materials from garbage management were also included among standard filtration media, such as recyclable paper and biochar (a product of microwave pyrolysis). The manipulation with and use of recycled material is in accordance with the strategic concept of a circular economy. 2.1. Parameters of Laboratory Measurement Filtration media testing was carried out in a filtration column with a reaction tank for the production of hydrogen sulphide. Hydrogen sulphide was produced using powdered ferric sulphide FeS in a reaction vessel, with a dosing of hydrochloric acid HCl diluted with distilled water (see Equation (1)) and using a peristaltic pump into the reaction chamber. FeS + 2HCl → H2 S + FeCl2
(1)
Molar mass of individual compounds Mr (FeS) = 87.834 g·mol−1 , Mr (H2 S) = 34 g·mol−1 . Amount of substance FeS = 0.0114 mol with a theoretical volume of 0.255 L. Constant flow monitoring was provided by manometer and anemometer detectors with a control system. Measurement of hydrogen sulphide concentration at the inlet and outlet of the filter column was performed by a detector with a datalogger, manufactured by OdaLog Logger L2, with the following parameters:
• •
input detector: LL-H2 S-1000, declared measuring range of 0–1000 ppm with a resolution of 0.5 ppm and detector accuracy of 0.5%, output detector: LL-H2 S-200, declared measuring range of 0–200 ppm with a resolution of 0.1 ppm and detector accuracy of 1%. Recorded measuring range of 350 ppm with a resolution of 0.1 ppm.
All the tested filtration media had the same boundary conditions set for laboratory measurements, which were calculated or verified during operation. The filtration media efficacy testing parameters for hydrogen sulphide removal filters are:
• • • • • • •
volume of one tested filtration medium: 0.5 L; maximum concentration of hydrogen sulphide at the inlet to the filtration unit: 300 ppm; maximum duration of one test: 30 min; hydrochloric acid concentration—HCl: 35%; dilution ratio with distilled water: 1:8; FeS volume: 1 gram; air flow rate set by anemometer: 3 L·min−1 . Laboratory conditions for measuring the efficiency of filtration media:
• • • • •
all filtration products were stored in a dry laboratory environment; testing was performed at a constant temperature of 20 ◦ C; air humidity was maintained at 55%; atmospheric pressure in the room equalled 1013.25 hPa; and constant temperature of the filtration media was 20 ◦ C.
The laboratory space was aired out after each measurement, along with a control measurement for H2 S neutral odour and calibration of both H2 S detectors. The testing of each filtration medium took place on three occasions to ensure sufficient measured data for statistical evaluation. Before the laboratory tests, the anemometer was used to determine the actual airflow values in the sewerage. The air flow set through the filter column in the laboratory was selected with a 100% reserve.
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2.2. Filtration The filter media tested Media are divided into three basic groups according to structure, these being 2.2. Filtration The filterMedia media tested are divided into three basic groups according to structure, these being 2.2. Filtration Media 2.2. Filtration Media The filter media are divided into three basic according to structure, these being pelletized materials, granulates andtested gels—see Tables 3–5. 2.2. Filtration Media pelletized materials, gels—see Tables 3–5.groups The filter mediagranulates tested are and divided into three basic groups according to structure, these being The filter filter mediagranulates tested are areand divided into three three basic groups according to to structure, these these being pelletized materials, gels—see Tablesbasic 3–5. groups The media tested divided into pelletized materials, gels—see Tablesbasic 3–5. groups according The filter mediagranulates tested areand divided into three according to structure, structure, these being being pelletized materials, granulates and gels—see Tables 3–5. pelletized. Table 3. Selected filter medium pelletized materials, granulates and gels—see Tables 3–5. Table 3. Selected filter medium pelletized. pelletized materials, granulatesTable and gels—see Tables 3–5. 3. Selected filter medium pelletized.
Filtration Medium
Activated carbon extruded Identification: AddSorb VA3
Biochar I
Biochar II
Product Identification: Biofilter Rehau
Filtration Medium
Clayey granulate Identification: Granulit Air
Natural mineral Zeolite
Natural mineral Identification: Grena GV Vermicularis
Table 3. Selected filter medium pelletized. Filtration Medium Description Manufacturer Structure Table 3. 3. Selected Selected filter medium medium pelletized. pelletized. Table filter Filtration Medium Description Manufacturer Structure Table 3. Selected filter mediumStructure pelletized. Description Manufacturer Filtration Medium Description Manufacturer Structure for Filtration Medium Medium Intended Description Manufacturer Structure Filtration Description Manufacturer Structure Activated carbon Jacobi Carbons for Filtration Medium Intended Description Manufacturer gaseous phase BulkStructure material Intended for Activated carbon Jacobi Carbons extruded carbon ParentCarbons Company Activated Jacobi Intended for phase Bulk material Intended for gaseous gaseous based on graphite Granulometry Intended for gaseous phase Bulk material Activated carbon Jacobi Carbons extruded Parent Company Jacobifor Carbons Parent Identification: [25] Intended Activated carbon Jacobi Carbons extruded Parent Company gaseous phase Bulkmm material based on graphite Granulometry Bulk material phase based on graphite plates with a large 4–8 Activated carbon Jacobi Carbons gaseous phase Bulk material Company [25] based on graphite Granulometry extruded VA3 Parentin: Company Identification: [25] AddSorb Made Japan gaseous phase Bulk material extruded Parent Company Granulometry 4–8 mm plates with a large Identification: [25] based on graphite Granulometry plates with a large 4–8 mm internal surface. extruded VA3 Parentin: Company based on graphite Granulometry Made in: Japan plates with a large 4–8 mm Identification: [25] AddSorb Made Japan based on graphite Granulometry internal surface. Identification: [25] AddSorb VA3 Made in: Japan plates with with a large large 4–8 mm mm internal surface. Identification: [25] plates a 4–8 internal surface. AddSorb VA3 VA3 Made in: in: Japan Japan plates with a large 4–8 mm AddSorb Made Product of spruce Bionic E &Japan M, internal surface. AddSorb VA3 Made in: internal surface. Product of spruce Bionic E & M, internal surface. Biochar I wood microwave s.r.o. Product of spruce Bionic E & M, ProductIof spruce Product ofunit. spruce Bionic E& & M, Biochar wood microwave s.r.o. pyrolysis Brno University Product of spruce Bionic E Biochar I wood microwave s.r.o. Bionic E & M, s.r.o. Bulk material Product of spruce Bionic E & M, M, wood microwave Biochar II wood microwave microwave s.r.o. pyrolysis unit. Brno University of Technology, Biochar wood s.r.o. pyrolysis unit. University Bulk material Brno University ofBrno Granulometry pyrolysis Biochar I unit. wood microwave s.r.o. Bulk material pyrolysis unit. Brno University of Technology, Bulk material AdMaS Center Product of sewage pyrolysis unit. Brno University Technology, AdMaS of Technology, Bulk mm material Granulometry 2–10 pyrolysis unit. Brno University Bulk material Granulometry of Technology, AdMaS Center Granulometry 2–10 mm Product of sewage ProductIIof sewage [26] Biochar sludge microwave Bulk material of Technology, Center [26] AdMaS Center Granulometry Product of sewage 2–10 mm of Technology, Granulometry sludge microwave 2–10 mm AdMaS Center [26] Product of sewage Biochar II sludge microwave Made in: Czech pyrolysis unit. Granulometry Made in: Czech Republic AdMaS Center Product of sewage [26] 2–10 mm mm Biochar II sludge microwave AdMaS Product ofunit. sewage 2–10 pyrolysis [26] in:Center Made Czech Biochar II IIunit. sludge microwave microwave pyrolysis Republic 2–10 mm [26] Biochar sludge Made in: Czech pyrolysis unit. [26] Biochar II sludge microwave Made in: in: Czech Czech Republic pyrolysis unit. unit. Made pyrolysis Republic Made in: Czech pyrolysis unit. Republic Republic Rehau company Republic Product Recyclable old Bulk material Rehau [27] company Recyclable old paper Recyclable Rehau old company [27] Bulk material Rehau company Product Bulk material Identification: paper without Granulometry Product Recyclable old Bulk material Rehau company [27] Made in: without black ink. Made in: Switzerland Granulometry 5–30 mm Rehau company [27] Product Recyclable old Bulk material Identification: paper without Granulometry Biofilter Rehau black ink. 5–30 mm Rehau company Product Recyclable old Bulk material Identification: paper without Granulometry [27] Made in: Switzerland Product Recyclable old Bulk material [27] Made in: Identification: paper without Granulometry Biofilter Rehau black ink. 5–30 mm [27] in: Identification: paper without Granulometry Biofilter Rehau black ink. 5–30 mm Made Switzerland Identification: paper without Granulometry Made in: Switzerland Biofilter Rehau Rehau black ink. ink. 5–30 mm mm Made in: Biofilter black 5–30 Switzerland Biofilter Rehau black ink. 5–30 mm Switzerland Switzerland Table 4. Selected filter medium granulates. Table 4. Selected medium granulates. Tablefilter 4. Selected filter medium granulates. Table 4. SelectedManufacturer filter medium granulates. Structure Filtration Medium Description Table 4. Selected filter medium granulates. Table filter Structure Filtration Medium Description Table 4. 4. Selected SelectedManufacturer filter medium medium granulates. granulates. Structure Filtration Medium Description Manufacturer Description Manufacturer Manufacturer Structure Strong deodorizing Structure Filtration Medium Description Structure Filtration Medium Description Manufacturer Strong deodorizing Structure Filtration Medium Description Manufacturer Clayey granulate agent. Porous Biothys asia co., Bulk material Strong deodorizing Strong deodorizing Clayey granulate agent. Porous Biothys asia co., Bulk material Identification: granulate, excellent Ltd. [28] Granulometry Strong deodorizing Clayeydeodorizing granulate agent. Porous Biothys asia co., Bulk material Strong Strong deodorizing Clayey granulate granulate agent. Porous Porous Biothys asia co., Granulometry Bulkmm material Identification: granulate, excellent Ltd. [28] decomposition of Made in:asia Korea Granulit Air 4–8 Clayey agent. Biothys Bulk material Identification: excellent Ltd. [28] Granulometry agent. Porous granulate, granulate, Biothys asia co., Ltd. [28] Bulkco., material Clayey granulate agent. Porous Biothys co., Bulk material Identification: granulate, excellent Ltd. [28] [28] Granulometry decomposition of Made in:asia Korea Granulit Air 4–8 mm organic substances. Identification: granulate, excellent Ltd. Granulometry excellent decomposition decomposition Made in:excellent Korea 4–8 mm of Made in:Granulometry Korea 4–8 Granulit Air mm Identification: granulate, Ltd. [28] Granulometry decomposition of Made in: Korea Granulit Air 4–8 mm organic substances. decomposition of Made Granulit of organicAir substances. organic substances. decomposition of Made in: in: Korea Korea 4–8 Granulit Air 4–8 mm mm organic substances. substances. organic organic substances. Alkali metal Subio, s.r.o. Bulk material Alkali metal Subio, Natural mineral aluminosilicate [29] s.r.o. Alkali metal Subio, s.r.o. Bulk material Granulometry Bulk material Alkali metal Subio, s.r.o. Natural mineral aluminosilicate [29] Zeolitemetal crystalline and Made in: Czech Granulometry Alkali metal Subio, s.r.o. Natural mineral aluminosilicate [29] Bulk material material Alkali 2.5–5 mm Alkali metal Subio, s.r.o. Bulk Granulometry Natural mineral aluminosilicate [29] Zeolite crystalline and Made in: Czech alkaline earth metals. Republic Bulk material Natural mineral aluminosilicate [29] aluminosilicate Subio, s.r.o. material Zeolite crystalline and [29] Made in:Bulk Czech Granulometry 2.5–5 mm Natural mineral aluminosilicate [29] Granulometry 2.5–5 mm Zeolite crystalline and Made in: Czech alkaline earth metals. Republic Granulometry crystalline and alkaline alkaline Madeearth in:and Czech Republic Granulometry Zeolite crystalline Made in: Republic 2.5–52.5–5 mmmm Zeolite crystalline andmetals. Made in: Czech Czech 2.5–5 alkaline earth earth metals. Republic Republic earth metals. 2.5–5 mm mm alkaline Mineralalkaline earth metals. metals. Republic Mineralphyllosilicates. This MineralNatural mineral Grena, a.s. [30] Bulk material Mineralphyllosilicates. This serves as a carrier Mineralphyllosilicates. This Natural mineral Grena, a.s.Czech [30] Bulk material Identification: Grena Made in: Granulometry MineralNatural mineral Grena, a.s. [30] Bulk material phyllosilicates. This serves as gels a carrier layer for that phyllosilicates. This Mineral-phyllosilicates. serves as a carrier Natural mineral Grena, a.s. [30] Bulk material Identification: Grena Made in: Czech Granulometry GV Vermicularis Republic 0–5 mm phyllosilicates. This Natural mineral Grena, a.s. [30] Bulk material Identification: Made in: Czech Granulometry serves asgels a carrier carrier for that soak into GV and do Natural mineral Grena, a.s. [30] Bulk material This serves as aGrena carrier layer serves as a layer for gels that Identification: Grena Made in: Czech Granulometry GV Vermicularis Republic 0–5 mm serves as a carrier Grena, a.s. [30] Bulk material Identification: Grena Made in: Czech Granulometry GV Vermicularis Republic 0–5 mm layer for gels gels that into GV do not cause theirand loss. Identification: Grena Made in: Czech Granulometry layer for gels that soak soak layer for that soak into GV and do GV Vermicularis Republic 0–5 mm Made in: Czech Republic Granulometry 0–5 mm layer for gels that GV Vermicularis Republic 0–5 soakcause into their GV and and do not loss. into and do not GV GV Vermicularis Republic 0–5 mm mm soak into GV do not cause their loss. soak into GV and do not cause their loss. cause their loss. not not cause cause their their loss. loss.
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filter medium gels.
Table Table5. 5.Selected Selectedfilter filtermedium mediumgels. gels. Table 5. Selected filter medium gels. Table 5. Selected filter medium gels. Filtration Medium Filtration Medium Description Description Manufacturer Structure Structure Manufacturer Structure FiltrationMedium Medium Description Manufacturer Structure Filtration Description Manufacturer Structure Filtration Medium Description Manufacturer Mixture OMI Industries, Mixtureof ofnatural natural OMI OMIIndustries, Industries, Mixture of natural Milky gel Mixture Milkywhite white gel of natural Mixture of natural OMI Industries, Milky white gel oils and co. OMI Milky white gel essential oils andIndustries, co.[31] [31]co. [31] Milky white gel oils andessential essential oils and co. [31] Identification: essential food Identification: essential oils and co. [31] Identification: Ecosorb Identification: 505 food Made in: foodgrade grade Made in: USA, MadeIllinois in:USA, USA, Identification: food grade Made in: USA, Ecosorb 505 Ecosorbgrade 505 emulsifiers. food grade Made in: USA, Ecosorb 505 emulsifiers. Illinois emulsifiers. Illinois Ecosorb 505 emulsifiers. Illinois emulsifiers. Illinois
Milky white gel Identification: Ona Gel Liquid
Blue gel Identification: Bad Air Sponge
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Gel form Gel form Gel form Gel form Gel form
Mixture Mixtureof of Mixture of Mixture of hydrocarbons of hydrocarbonsof of hydrocarbons Odorchem Odorchem hydrocarbons of Mixture Odorchem Milky gel plant and Milkywhite white gel of hydrocarbons plantorigin originOdorchem and Odorchem Manufacturing Milky white gel plant origin and Manufacturing Manufacturingco. co. Gel balls Milky white gel plant origin and of plant origin and Manufacturing co. Identification: Ona chemical balls Identification:Ona Ona chemical co. [32] [32] Gel balls Manufacturing co. Gel Identification: chemical Gel balls chemical compounds for [32] Identification: Ona chemical Gel balls [32] Gel Liquid compounds for Made in: Canada Gel Liquid compounds for [32] Gel Liquid compounds for Made in: Canada odour neutralization. Madein: in:Canada Canada Gel Liquid compounds for Made odour odour Made in: Canada odour odour neutralization. neutralization. neutralization. neutralization. Gel Gelcontaining containing Gel containing Mateson MatesonChemical Chemical Gel containing Mateson Chemical Blue activated Mateson Chemical Bluegel gelGel containing activated activatedcarbon, carbon, Mateson Chemical Blue gel activated carbon, Corporation [33] Corporation [33] Blue gel activated carbon, Corporation [33] Corporation [33] Identification: Bad wetting and Semi-solid gel Identification: Bad wetting and Semi-solid gel Corporation [33] Semi-solid Identification: Bad wetting and Semi-solid gelgel carbon, wetting and Made in: USA, Made in: USA, Identification: Bad wetting andMade in: USA, Semi-solid gel Made in: USA, Air Sponge neutralizing AirSponge Sponge neutralizing Made in: USA, neutralizing agents. Air neutralizing Philadelphia Philadelphia Air Sponge neutralizingPhiladelphia Philadelphia agents. agents. Philadelphia agents. agents.
Gel Gelplate plate Gel plate Gel plate active Orange gel containing Biothys GmBH Orangegel gel containingactive active BiothysGmBH GmBH Orange containing Biothys Orange gel containing active Biothys GmBH Orange gel Gel plate containing Identification: substances [34] Gel Identification: substancesin inthe the GmBH [34] [34] Gelplate plate Biothys Identification: substances in the [34] Gel plate Identification: substances in the [34] in: Germany Gel Gel plate Identification: Gelactiv Gelactiv active substancesneutralization in the plate Made GelactivSuspension Suspension neutralization Madein: in:Germany Germany Made in: Germany Gelactiv Suspension neutralization Made Suspension Gelactivneutralization Suspension process. neutralization Made in: Germany process. process. process. process.
The The recyclable recyclable material materialis is the the cellulosic cellulosicbiofilter biofilter Rehau Rehau containing containingnutrients. nutrients. The The secondary secondary raw raw The recyclable material is cellulosic biofilter Rehau nutrients. The secondary raw The is recyclable material is the the cellulosic biofilter Rehau containing containing nutrients. The secondary raw material biochar, the product of the microwave pyrolysis process. The pyrolysis unit material is is biochar, biochar, the the product product of of the the microwave microwave pyrolysis pyrolysis process. process. The The pyrolysis pyrolysis unit unit is is located located in in material is located in The recyclablethe material is the the cellulosic biofilter Rehaupyrolysis containing nutrients. Theunit secondary raw material is biochar, product of the microwave process. The pyrolysis is located in the laboratories laboratories of of AdMaS AdMaS Research Research Center, Center, Technical Technical University University in in Brno, Brno, Faculty Faculty of of Civil Civil the laboratories of AdMaS Research Center, Technical University in Brno, Faculty of Civil the AdMaS Research Center, Technical University in Brno, of Civil material is biochar,Engineering. thelaboratories product ofofthe microwave pyrolysis process. The pyrolysis unit Faculty is located in the Engineering. Engineering. Engineering. Spruce wood was used for the microwave pyrolysis (filtration medium Biochar I in Table 1) laboratories of AdMaSSpruce Research University in (filtration Brno, Faculty ofBiochar Civil IEngineering. Spruce woodCenter, was usedTechnical for themicrowave microwave pyrolysis (filtration medium Biochar I inTable Table1) 1)and and wood was for pyrolysis medium Spruce wood was used usedwastewater for the the microwave pyrolysis (filtration medium Biochar I in in Table 1) and and sludge from the municipal treatment plant in Karlovy Vary, Czech Republic (filtration sludge from the municipal wastewater treatment plant in Karlovy Vary, Czech Republic (filtration from the municipal wastewater treatment plant in Karlovy Vary, Czech Republic (filtration Spruce wood sludge was used for the microwave pyrolysis (filtration medium Biochar I in Table 1) and sludge from the municipal wastewater treatment plant in Karlovy Vary, Czech Republic (filtration medium medium Biochar Biochar II II in in Table Table 1) 1) with with aaa design design capacity capacity of of 80,000 80,000 PE. PE. medium Biochar II in Table 1) with design capacity of 80,000 PE. sludge from the municipal wastewater treatment plant in Karlovy Vary, Czech Republic (filtration medium Biochar II in Table 1) with a design capacity of 80,000 PE. Biochar Biochar III is is a pyrolysis product product produced produced without without admixtures. admixtures. Biochar Biochar II II is is aa pyrolysis pyrolysis product product Biochar is aaa pyrolysis pyrolysis product produced without admixtures. Biochar II is product Biochar Isludge iswith pyrolysis product produced without admixtures. Biochar IIadmixture is aa pyrolysis pyrolysis product medium Biochar IIfrom in Table 1) a design capacity of 80,000 PE. sewage with an organic dry matter content of 55% and a zeolite from sewage sewage sludge sludge with with an an organic organic dry dry matter matter content content of of 55% 55% and and aa zeolite zeolite admixture admixture at at aaa weight weight from at from sewage sludge withbiochar an organic dry matter content of 55% and a zeolite admixture at a weight weight of from sludge the subject of at Biochar I is a concentration pyrolysis product produced without admixtures. Biochar II is a pyrolysis product concentration of 1%. 1%. The The biochar yield yield from sewage sewage sludge is is currently currently the subject of research research at the the concentration of 1%. The biochar yield from sewage sludge is currently the subject of research the concentration of 1%. The biochar yield fromWithout sewage sludge is currently the subject of research at at the Brno University of AdMaS. admixtures, the sludge yield Brno University of Technology, Technology, AdMaS. Without admixtures, the sewage sewage sludge biochar biochar yield Brno University of Technology, AdMaS. Without admixtures, the sewage sludge biochar yield from sewage sludge with an organic dry matter content of 55% and a zeolite admixture at a weight Brno University of Technology, AdMaS. Without admixtures, the sewage sludge biochar yield contains contains a a small small amount amount of of organic organic matter matter (up (up to to 23%) 23%) and and liquid liquid (up (up to to 10%). 10%). Biochar Biochar II II contains contains contains aabiochar small amount of organic matter (up to 23%) and liquid (up to 10%). Biochar II contains concentration of 1%. The yield from sewage sludge is currently the subject of research at the contains small amount of organic matter (up to 23%) and liquid (up to 10%). Biochar II contains organic organicmatter matterthermogravimetrically thermogravimetrically40.3%, 40.3%,Total Totalorganic organiccarbon carbon(TOC) (TOC)biochar biochar29.3%, 29.3%,biochar biocharyield yield organic matter thermogravimetrically 40.3%, Total organic carbon (TOC) biochar 29.3%, biochar yield organic matter thermogravimetrically 40.3%, Total organic carbon (TOC) biochar 29.3%, biochar yield Brno University of58.9%, Technology, AdMaS. Without admixtures, the sewage sludge biochar yield contains 58.9%, liquid yield 18.2% and gas yield 22.9%. 58.9%, liquid liquid yield yield 18.2% 18.2% and and gas gas yield yield 22.9%. 22.9%. 58.9%, liquid yield 18.2% and gas yield 22.9%. A GV natural mineral was in with Gel a small amount of organic matter (up to 23%) and liquidtest (up tocarried 10%).out Biochar II contains organic A Grena Grena GV Vermicularis Vermicularis natural mineral test was carried out in combination combination with Ona Ona Gel A Grena GV Vermicularis natural mineral test carried out in with Gel A Grena GV Vermicularis natural mineral test was was carriedGV outVermicularis in combination combination with Ona Ona Gel Liquid and Ecosorb 505 milk gels. The ratio between the Grena filtration material Liquid and Ecosorb 505 milk gels. The ratio between the Grena GV Vermicularis filtration material Liquid and Ecosorb 505 milk gels. The ratio between the Grena GV Vermicularis filtration material matter thermogravimetrically 40.3%, Total organic carbon (TOC) biochar 29.3%, biochar yield 58.9%, Liquid and Ecosorb 505 milk gels. The was ratioexperimentally between the Grena GV Vermicularis filtration material and and the the Ona Ona Gel Gel and and Ecosorb Ecosorb 505 505 gels gels was was experimentally experimentally established established at at 1:1. 1:1. The The gel gel producers producers do do the Ona Gel and Ecosorb 505 established liquid yield 18.2% and and gas yield 22.9%. and the Ona Gelany and Ecosorb ratio 505 gels gels was experimentally established at at 1:1. 1:1. The The gel gel producers producers do do not recommend optimum with other filtration materials. not recommend recommend any any optimum optimum ratio ratio with with other other filtration filtration materials. materials. not recommend any optimum ratiofiltration with other filtration materials. A Grena GV not Vermicularis natural mineral test was carried combination with Ona Gel The of media, i.e., main and secondary of The basic basic composition composition of all all filtration filtration media, i.e., the the out mainin and secondary components components of the the The basic composition of all media, i.e., the main and secondary components of the The basic composition of all filtration media, i.e., the main and secondary components of the the media are listed by the manufacturer in the product data sheets and have not been tested by Liquid and Ecosorb 505 milk gels. The ratio between the Grena GV Vermicularis filtration material media are listed by the manufacturer in the product data sheets and have not been tested by the media media are are listed listed by by the the manufacturer manufacturer in in the the product product data data sheets sheets and and have have not not been been tested tested by by the the laboratory. laboratory. laboratory. and the Ona Gel and Ecosorb 505 gels was experimentally established at 1:1. The gel producers do not laboratory. No material inoculation was performed and there was no conditioning, stability of the material No material inoculation inoculation was was performed performed and and there was was no conditioning, conditioning, stability stability of the the material No recommend any optimum ratiomaterial with otherwas filtration materials. No material material inoculation performed and there there was no no conditioning, stability of of the material material during during the the test, test, material material compaction, compaction, and and water water retention retention in in the the material. material. The The damping damping capacity capacity of of during the test, compaction, and water retention in the material. The damping capacity of during the test, material compaction, and water retention in the material. The damping capacity of The basic composition of all filtration media, i.e., the main and secondary components of the media the filtration media was not evaluated. the filtration filtration media media was was not not evaluated. evaluated. the the filtration media was not evaluated.
are listed by the manufacturer in the product data sheets and have not been tested by the laboratory. No material inoculation was performed and there was no conditioning, stability of the material during the test, material compaction, and water retention in the material. The damping capacity of the filtration media was not evaluated. 3. Results
The evaluation of overall efficiency of filtration media used an original multi-criteria analytical method—see Table 6. Among the evaluation criteria were: effectiveness of the filtration medium,
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sorption capacity of the filtration medium, preparation of the filtration medium prior to the experiment into the filtration column and the odour impression. The service life of the filtration media is set by each manufacturer in the product data sheets. The preparation of the filtration material is an indicator defining a collection of works prior to testing of the filtration material. Preparation works included manipulation of the material, its treatment prior to filling, and emptying the test cartridge. Residual odour perception was evaluated at the end of laboratory testing for all filtration materials and is based on the sensory sensitivity of an experienced laboratory worker. Purchase price of the filtration material was not included in the evaluation criteria due to varied stock levels of the suppliers, various specific costs regarding their purchase, our own production costs and varying costs of material delivery. Mathematically, the evaluation of the overall efficiency of the material can be expressed using Equation (2). ui =
n
∑ v j . Cji
(2)
j =1
where: i—1, 2, . . . p, ui —general assessment of i-media; vj —rate of importance of j-criterion; Cj i —sub-assessment of i-media based on j-criterion; n—number of criteria; p—number of media. Table 6. Proposed evaluation criteria of filtration media. Classification at the Level Group of Criteria— Indicator Weight
Category Description Criterion Weight
Category C1—0.70
Filtration medium effectiveness
Category C2—0.15
CI
CII
CIII
CIV
0.1
0.15
0.25
0.5
>90%
70–90%
70–50%
12 months
6–12 months
3–6 months
