{"id":202,"date":"2026-07-09T08:53:14","date_gmt":"2026-07-09T08:53:14","guid":{"rendered":"https:\/\/industrialelectricmotor.net\/?p=202"},"modified":"2026-07-09T08:53:14","modified_gmt":"2026-07-09T08:53:14","slug":"explosion-proof-motor-for-wastewater-treatment-plant","status":"publish","type":"post","link":"https:\/\/industrialelectricmotor.net\/el\/explosion-proof-motor-for-wastewater-treatment-plant\/","title":{"rendered":"Explosion-Proof Motor for Wastewater Treatment Plant"},"content":{"rendered":"
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Korea Ever-Power \u00b7 YB2 Series \u00b7 Wastewater Treatment Drive Guide<\/span><\/p>\n

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Explosion-Proof Motor for Wastewater Treatment Plant:
\nSludge Pump, Digester and Gas Zone Drive Guide<\/span><\/h1>\n

Wastewater treatment plants handle multiple hazardous substances simultaneously: sewage sludge containing hydrogen sulphide (H\u2082S) released during digestion, biogas (primarily methane) generated in anaerobic digesters, and industrial effluent containing volatile organic solvents. The motor requirements across the plant vary by location: anaerobic digester areas require explosion-proof motors for methane gas zones, H\u2082S extraction areas require Ex d certification for the sulphide gas group, and outdoor sludge pump areas require IP55 with corrosion-resistant coatings. This guide covers the complete motor specification for wastewater treatment plant drives using the Korea Ever-Power YB2 series.<\/p>\n

Ex d IIB T4 Biogas<\/span>
\nZone 1 Digester Area<\/span>
\nIP55 Outdoor<\/span>
\nH\u2082S Resistant Coating<\/span>
\n0.55\u2013200 kW<\/span><\/div>\n<\/div>\n<\/div>\n

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IIB<\/div>\n
Methane and biogas group<\/div>\n<\/div>\n
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T4<\/div>\n
135\u00b0C surface limit<\/div>\n<\/div>\n
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Zone 1<\/div>\n
Digester building interior<\/div>\n<\/div>\n
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IP55<\/div>\n
Outdoor sludge area<\/div>\n<\/div>\n
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H\u2082S<\/div>\n
Sulphide resistant coating<\/div>\n<\/div>\n<\/div>\n

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\"Explosion<\/p>\n
Korea Ever-Power YB2 series Ex d IIB T4 explosion-proof motor \u2014 the certified motor specification for all Zone 1 and Zone 2 locations in anaerobic digester buildings, biogas handling areas, and sludge dewatering facilities at wastewater treatment plants where methane and hydrogen sulphide gas mixtures may be present.<\/div>\n<\/div>\n

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Contents<\/div>\n
1. Wastewater Plant Hazardous Gas Zones<\/a>
\n2. Biogas and H\u2082S Gas Group Classification<\/a>
\n3. Anaerobic Digester Zone Classification<\/a>
\n4. Sludge Area IP55 and Corrosion Protection<\/a>
\n5. H\u2082S Attack on Standard Motor Coatings<\/a>
\n6. YB2 for Wastewater Treatment Applications<\/a>
\n7. Wastewater Treatment Applications<\/a>
\n8. Frequently Asked Questions<\/a><\/div>\n<\/div>\n

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1. Wastewater Treatment Plant Hazardous Gas Zones<\/h2>\n

A modern wastewater treatment plant has several distinct areas with different hazardous gas risks. Not every area of the plant requires explosion-proof motors \u2014 the aeration basins, clarifiers, and chemical dosing areas of a standard municipal wastewater plant operate in non-classified conditions \u2014 but the areas handling biogas, sludge, and industrial effluent require careful hazardous area classification.<\/p>\n

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Zone 1 \u2014 Digester Interior and Adjacent Areas<\/div>\n

Anaerobic digester building interiors, biogas storage balloon interiors, biogas pipe galleries, and areas within 1 m of biogas valve and fitting clusters. Biogas is primarily methane (60 to 70%) with CO\u2082 and traces of H\u2082S. Methane is classified IIA (auto-ignition 537\u00b0C). The combined biogas mixture is classified IIB due to the H\u2082S content. All motors in Zone 1 digester areas must be YB2 Ex d IIB T4. This includes biogas compressor motor drives, digester mixing pump motors, and any electrical equipment mounted in the digester building.<\/p>\n<\/div>\n

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Zone 2 \u2014 Digester Building Perimeter<\/div>\n

The area outside the digester building within 3 m of any ventilation outlet, access hatch, or pipe entry is typically Zone 2. Biogas may be present in this perimeter zone during maintenance activities, ventilation system anomalies, or minor gas leakage from flanged joints. Outdoor motors in Zone 2 perimeter areas must be YB2 Ex d IIB T4 or equivalent Zone 2 certified motors \u2014 standard Y2 motors are not acceptable even in outdoor Zone 2 areas.<\/p>\n<\/div>\n

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H\u2082S Exposure \u2014 Non-Classified but Corrosive<\/div>\n

Hydrogen sulphide is released from sludge in concentrations that are typically below the explosive range (LEL 4% in air) but above the toxic odour threshold and above the level that aggressively attacks copper, silver, and iron-based coatings. Sludge thickening areas, dewatering buildings, and sludge drying beds may not be classified as hazardous zones for explosion risk (if H\u2082S concentrations remain below 25% LEL), but all motors in these areas must be specified with H\u2082S-resistant coatings and sealed terminal boxes to prevent rapid corrosion of electrical components.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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2. Biogas and H\u2082S Gas Group Classification<\/h2>\n
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Wastewater Gas Hazard Summary<\/div>\n
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Methane (CH\u2084)<\/div>\n
Gas group: IIA
\nLEL: 5% v\/v in air
\nUEL: 15% v\/v
\nAuto-ignition: 537\u00b0C
\nT class required: T1
\nYB2 IIB T4: covers IIA<\/div>\n<\/div>\n
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Hydrogen Sulphide (H\u2082S)<\/div>\n
Gas group: IIB
\nLEL: 4% v\/v in air
\nUEL: 46% v\/v
\nAuto-ignition: 260\u00b0C
\nT class required: T3
\nYB2 IIB T4: covers IIB T3<\/div>\n<\/div>\n
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Biogas Mixture<\/div>\n
60\u201370% CH\u2084, 30\u201340% CO\u2082, 0.5\u20132% H\u2082S
\nH\u2082S content drives group to IIB
\nT class: T3 for H\u2082S component
\nYB2 IIB T4 covers all biogas
\nATEX + IECEx certified<\/div>\n<\/div>\n
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YB2 IIB T4 Coverage<\/div>\n
Group IIB covers methane (IIA) and H\u2082S (IIB). T4 at 135\u00b0C max surface provides adequate margin above H\u2082S auto-ignition (260\u00b0C). Single YB2 IIB T4 specification covers all wastewater biogas zone requirements.<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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3. Anaerobic Digester Zone Classification in Practice<\/h2>\n
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Digester Building \u2014 Zone 1 Throughout<\/div>\n

A covered digester building (common in cold climates where the digester must be protected from freezing) is classified as Zone 1 throughout its interior because biogas can accumulate within the building envelope at explosive concentrations if ventilation fails or during maintenance access to the digester. All motors inside the digester building \u2014 sludge recirculation pumps, mixing pump drives, gas compressor drives, and heat exchanger pump drives \u2014 must be YB2 Ex d IIB T4. The electrical classification applies even to motors in corridors and service areas within the building boundary.<\/p>\n<\/div>\n

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Open-Top Digester \u2014 Zone 1 Above Cover<\/div>\n

Egg-shaped or cylindrical digesters with a floating gas cover have Zone 1 above the gas cover and within 1 m of the gas relief valve, gas outlet connection, and level measurement connections. Zone 2 extends from 1 to 3 m beyond the Zone 1 boundary. Any external mixer motor mounted on the digester wall or roof within the Zone 1 boundary must be YB2 Ex d IIB T4. External agitator drives on the digester wall may be in Zone 2 if their mounting position is more than 1 m from any gas outlet; confirm with the hazardous area classification drawing for the specific digester design.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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4. Sludge Pump Area IP55 and Corrosion Protection<\/h2>\n

Sludge handling areas outside the classified biogas zones still present a challenging motor environment: outdoor installation exposed to rain and hose-down cleaning; H\u2082S atmosphere at sub-LEL but aggressively corrosive concentrations (1 to 50 ppm H\u2082S); and regular hosing of concrete surfaces with water containing sludge and treatment chemicals. IP55 is the minimum enclosure rating and corrosion-resistant coating is essential for motors in these areas even where no explosion protection certification is required.<\/p>\n

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IP55 for Outdoor Sludge Areas<\/div>\n

Sludge pump stations, thickener drives, dewatering press drives, and centrifuge drives in outdoor sludge handling areas require IP55 as a minimum. Hose-down cleaning of concrete surfaces and equipment regularly directs water jets toward motor enclosures. IP55 protection against water jets prevents water ingress that would cause insulation deterioration in the H\u2082S atmosphere.<\/p>\n<\/div>\n

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Cast Iron vs Aluminium Frame in H\u2082S<\/div>\n

Cast iron frames (standard on YB2 Ex d series in IEC 112 and above) are more resistant to H\u2082S corrosion than painted aluminium frames used on standard Y2 motors up to IEC 100. When the paint coating is breached \u2014 by mechanical impact or UV degradation \u2014 the exposed aluminium oxidises and H\u2082S accelerates the corrosion. The YB2 cast iron frame with marine-grade epoxy primer and polyurethane topcoat provides superior longevity in H\u2082S environments.<\/p>\n<\/div>\n

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Sealed Terminal Box for H\u2082S<\/div>\n

H\u2082S attacks copper cable terminations and brass cable gland bodies rapidly \u2014 copper sulphide deposits form on terminal surfaces, increasing contact resistance and potentially causing connection overheating. The YB2 sealed IP55 terminal box prevents H\u2082S from entering and attacking the terminals. Specify tinned copper or stainless steel terminal inserts where H\u2082S concentrations above 10 ppm are expected.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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5. H\u2082S Attack on Standard Motor Coatings<\/h2>\n
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Standard Motor vs YB2 in Wastewater H\u2082S Environment<\/div>\n
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Standard Y2 aluminium motor in H\u2082S sludge area:<\/div>\n
Year 1: Paint blistering at scratches and bolt hole edges from H\u2082S acid attack under paint film \u2192 Year 2: Exposed aluminium pitting, white oxide deposits on frame surface \u2192 Year 3: Severe pitting corrosion through frame wall in some areas, insulation resistance begins to fall from H\u2082S and moisture ingress \u2192 Year 4\u20135: Motor replacement required.<\/div>\n<\/div>\n
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YB2 cast iron with marine epoxy coating:<\/div>\n
Year 1\u20135: Coating maintains integrity; H\u2082S does not reach cast iron substrate \u2192 Year 5: Touch-up coating applied at maintenance interval to any minor impact damage \u2192 Year 10+: Motor continues in service with annual inspection and touch-up; IP55 sealed terminal box prevents H\u2082S attack on copper cable terminations throughout service life.<\/div>\n<\/div>\n<\/div>\n<\/div>\n

The economic case for specifying YB2 in H\u2082S wastewater environments is compelling even where no explosion protection is technically required. The 2 to 3 times longer service life of the YB2 cast iron motor over a standard Y2 aluminium motor in H\u2082S atmosphere saves more in reduced replacement and labour cost than the initial premium cost of the YB2 within its first replacement cycle.<\/p>\n<\/div>\n

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6. Korea Ever-Power YB2 for Wastewater Treatment<\/h2>\n
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The Korea Ever-Power YB2 Ex d IIB T4 provides a single motor specification that covers both Zone 1\/2 explosion protection for biogas areas and the superior corrosion resistance needed in H\u2082S sludge handling areas. The cast iron IP55 enclosure resists H\u2082S corrosion for service lives exceeding 10 years in wastewater environments. The Ex d IIB T4 certification covers both methane (IIA) and hydrogen sulphide (IIB) gas groups with a single motor type, simplifying the motor specification and spare parts inventory across the entire wastewater plant. The complete YB2 range is in the explosion-proof motor section<\/a>. For large wastewater plant pump and blower motor specifications above 75 kW, contact Korea Ever-Power<\/a>.<\/p>\n<\/div>\n

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YB2 \u2014 Wastewater Plant Data<\/div>\n\n\n\n\n\n\n\n\n\n\n
Certification<\/td>\nATEX + IECEx Ex d IIB T4<\/td>\n<\/tr>\n
Gas coverage<\/td>\nMethane IIA + H\u2082S IIB<\/td>\n<\/tr>\n
Zone suitability<\/td>\nZone 1 and Zone 2<\/td>\n<\/tr>\n
Frame<\/td>\nCast iron (H\u2082S resistant)<\/td>\n<\/tr>\n
IP rating<\/td>\nIP55<\/td>\n<\/tr>\n
Coating<\/td>\nMarine epoxy + polyurethane<\/td>\n<\/tr>\n
Power range<\/td>\n0.55\u2013200 kW<\/td>\n<\/tr>\n
Surface temp<\/td>\nT4 = 135\u00b0C maximum<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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7. Wastewater Treatment Plant Applications<\/h2>\n\n\n\n
\"Explosion<\/p>\n
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Anaerobic Digester Mixing and Gas Handling<\/div>\n

Digester sludge recirculation pump drives (5.5 to 22 kW, Zone 1), biogas recirculation compressor motors (7.5 to 30 kW, Zone 1), gas mixing nozzle pump drives (3.0 to 11 kW, Zone 1), and digester heat exchanger pump drives (1.5 to 7.5 kW, Zone 1 or 2). All must be YB2 Ex d IIB T4. In digester buildings with mechanical ventilation, the ventilation fan motors are also in Zone 1 if mounted inside the building, and must be YB2 certified.<\/p>\n<\/div>\n<\/td>\n

\"Explosion<\/p>\n
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Sludge Handling and Dewatering<\/div>\n

Raw sludge pump drives (3.0 to 22 kW), thickener rake drive motors (0.75 to 5.5 kW), belt press and centrifuge feed pump motors (2.2 to 15 kW), and sludge cake conveyor drives (0.55 to 3.0 kW). These areas may be non-classified for explosion but require H\u2082S resistant coating and IP55. YB2 provides both explosion protection and corrosion resistance as a single motor specification across the whole plant.<\/p>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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Biogas CHP Engine Ancillaries<\/div>\n

Biogas combined heat and power (CHP) engine cooling water pump drives and engine room ventilation fans. Engine room is Zone 1 inside biogas engine enclosure and Zone 2 in engine room area. YB2 1.5 to 11 kW for cooling pump and fan drives within engine room boundary.<\/p>\n<\/div>\n

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Biogas Upgrading Plant<\/div>\n

Biomethane upgrading plants (pressure swing absorption or membrane separation) compress biogas to grid injection quality. Compressor motor drives and all auxiliary pump and fan drives within the gas processing building are Zone 1. YB2 5.5 to 55 kW for compressor auxiliary drives.<\/p>\n<\/div>\n

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Industrial Effluent Treatment<\/div>\n

Industrial wastewater treatment handling VOC-contaminated effluent from chemical, food, or pharmaceutical plants. Where effluent contains flammable VOC above 25% LEL in the treatment vessel headspace, Zone 1 or Zone 2 classification applies. YB2 IIB T4 for all motors in classified zones.<\/p>\n<\/div>\n

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Screenings and Grit Handling<\/div>\n

Screen conveyor drives, grit classifier motors, and screening compactor drives at the plant inlet works. Exposed to H\u2082S from incoming sewage; non-classified for explosion but corrosive environment. YB2 0.55 to 3.0 kW for inlet works drives in place of standard Y2 for extended service life.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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\"Korea<\/p>\n

Cast Iron Machining<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Explosion Test<\/div>\n<\/div>\n
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\"Korea<\/p>\n

ATEX and IECEx<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Global Export<\/div>\n<\/div>\n<\/div>\n

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8. Frequently Asked Questions<\/h2>\n
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Does a municipal wastewater plant aeration basin motor need explosion-proof certification?<\/div>\n<\/div>\n
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No. The aeration basin of a municipal activated sludge plant is not a classified hazardous area because the wastewater being aerated is aerobic \u2014 there is no significant production of flammable gases at the concentrations required for explosive atmosphere classification. The surface aerator or submerged aeration blower motors in aeration basins are typically standard Y2 or YS motors with IP55 for outdoor service. Explosion-proof motors are required only in the anaerobic zones of the plant \u2014 principally the digester building, gas storage, and any enclosed sludge handling areas where biogas accumulation is possible. Always refer to the site hazardous area classification document, which must be prepared by a competent person for each wastewater treatment plant, before specifying motor types for any area of the plant.<\/p>\n<\/div>\n<\/div>\n

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What maintenance is required for YB2 motors in H\u2082S wastewater environments?<\/div>\n<\/div>\n
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In addition to standard electrical inspection (bearing condition, insulation resistance measurement, terminal box inspection), YB2 motors in H\u2082S wastewater environments require an annual visual inspection of the external coating condition. Any areas where paint has been damaged by impact, abrasion, or UV degradation should be touched up with marine-grade epoxy primer and polyurethane topcoat before corrosion progresses to the cast iron surface. For Zone 1 and Zone 2 motors, the IEC 60079-17 periodic inspection requirements also apply \u2014 confirming that all fasteners are present, the terminal box lid is correctly sealed, Ex d cable glands are tight, and the motor frame is not structurally corroded. Keep photographic records of each inspection to document the coating condition trend over the motor service life. In high H\u2082S areas above 50 ppm, reduce the inspection interval to every 6 months for the first 3 years of service to establish the actual corrosion rate at that location.<\/p>\n<\/div>\n<\/div>\n

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Can I use a VFD to control sludge pump speed in a wastewater plant digester area?<\/div>\n<\/div>\n
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Yes, and VFD speed control on digester sludge recirculation pumps provides significant energy savings and improves digestion process control. The VFD must be installed outside the Zone 1 classified area \u2014 in a separate MCC room or a pressurised Ex p enclosure. The motor connecting the VFD to the pump must be the YB2 Ex d IIB T4 regardless of VFD location. For the motor side, specify the YB2 with an IC416 forced cooling blower rather than the standard IC411 shaft-mounted fan, so the motor can deliver full torque at reduced pump speed without the cooling penalty of low-speed operation. This is particularly important for sludge recirculation pumps that operate at 30 to 70% of rated speed for most of the digestion cycle, where IC411 cooling would be inadequate. Contact Korea Ever-Power for YB2 IC416 option availability and specification for your pump power range.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Korea Ever-Power \u00b7 YB2 Series \u00b7 Wastewater Treatment Explosion-Proof Motors<\/div>\n

Need Certified Motors for Your Wastewater Treatment Plant?<\/h2>\n

Korea Ever-Power YB2: ATEX + IECEx Ex d IIB T4, IP55 cast iron, marine epoxy coating, 0.55\u2013200 kW. Covers biogas Zone 1\/2 and H\u2082S sludge areas with a single motor specification.<\/p>\n

View YB2 Explosion-Proof Range<\/a><\/p>\n<\/div>\n<\/div>\n

Edited by Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power \u00b7 YB2 Series \u00b7 Wastewater Treatment Drive Guide Explosion-Proof Motor for Wastewater Treatment Plant: Sludge Pump, Digester and Gas Zone Drive Guide Wastewater treatment plants handle multiple hazardous substances simultaneously: sewage sludge containing hydrogen sulphide (H\u2082S) released during digestion, biogas (primarily methane) generated in anaerobic digesters, and industrial effluent containing volatile organic solvents. […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[28],"tags":[],"class_list":["post-202","post","type-post","status-publish","format-standard","hentry","category-industrial-electric-motor"],"_links":{"self":[{"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/posts\/202","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/comments?post=202"}],"version-history":[{"count":1,"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/posts\/202\/revisions"}],"predecessor-version":[{"id":205,"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/posts\/202\/revisions\/205"}],"wp:attachment":[{"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/media?parent=202"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/categories?post=202"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/el\/wp-json\/wp\/v2\/tags?post=202"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}