Electric Dehydrator Technology Introduction

* Abstract of sludge dewatering technology
Sludge dewatering method is intended to eliminate water from sludge, to enhance operating cost reduction effect and resource values, as well as to reduce transportation cost up to the final disposal and to cause no trouble for land disposal techniques.

* Classification of sludge dewatering technology

a. Filtering dehydration method

01 Method by the drying bed
A method of infiltration drainage into the filter bed and drying on the surface after allowing the sludge flow on to the filter bed where sand or filtering materials have been laid

02 Drying Lagoon
A drying method to put sludge in the lagoon for precipitation, to send supernatant back to the disposal facility, and evaporate the sludge of 0.7~1.4m depth

b. Mechanical dewatering method

01 Vacuum dehydrator (Vacuum Filter)
- A dewatering method where the outer circumference of spin drum is covered by filtering cloth, negative pressure(300~600mmHg) in the drum inside is maintained by a vacuum pump, and the drum rotates.

02 Pressing dehydrator (Filter press)
- A dewatering method to pressurize the sludge wrapped by filtering cloth

03 Centrifugal dehydrator (Screw decanter)
- A dewatering method by gravity after receiving centrifugal effect of 1,000~3,000G resulting from rotating movement of solid particles

04 Belt press
- A method to dewater the sludge continuously by one or two moving belt.
- A dewatering method by gravity when the sludge reformed by organic polymer coagulant is injected into the belt press, and by pressure between rollers along the movement of belt.

05 Screw press
- A dewatering method by compressing and extruding the condensed sludge with screw

C. Analysis by the kinds of dehydrators

Item	Our technology	Existing technology
Dewatering type	Electric Dewatering	Filter press	Screw decanter	Belt press	Vacuum filter
Picture
Applied principle	Electric infiltration	Sludge supply pressure	Centrifugal force	Filter cloth	Decompression filtering
Applied agent	Not applicable	Polymer coagulant	Polymer coagulant	Polymer coagulant	Polymer coagulant
%of water content after dewatering	below 65wt%	80~70wt%	80~70wt%	80~70wt%	80~70wt%
Operating cost	Electricity cost	Added electricity cost of high pressure dewatering part	Less power consumption ratio	Added electricity cost of high pressure dewatering part	big energy consumption
Service pressure	Simple compression except for power supply	15kg/cm2	1500~3000G	10~20kg/m3/hr	10~25kg/m3/hr
Incidental facilities	Steam removal facility	Reaction facility Drug facility Cleaning facility	Cleaning facility Soundproof facility Dedusting facility	Reaction facility Drug facility	Agitating device in Vat Cleaning device Dewatered cake discharge conveyor
Sludge supply method	Continuous	Intermittent	Continuous	Continuous	Continuous
Applicability against sludge behavior change	Good	Good	Bad	Good	Ordinary
Others	Disposal efficiency varies with the quantity of power supply	Continuous work is difficult due to Batch type operation	Solid recovery is small. Issue of high rotation	Drug injection is required.	Intoxication Many incidental facilities

Principles and advantage of electric dewatering technology

Definition of Sludge

Sludge is called Oh-Nee in Chinese language.
Sludge in the dictionary means a solid substance settled down from the floating matters when sewage is precipitated in water tank or reservoir.
Diverse sludges are obtained during several stages of sewage treatment process. That is, at the first stage chemically settled sludge is obtained, then sludge activated by a drip filter is obtained, and retted sludge is obtained. Some sludge is sent to the ocean after treated with the underwater dumping method or water pumping method, some is sold as a fertilizer after being dried, and some is retted after anaerobic treatment in the water reserver like an imhoff tank or precipitation tank with microbes to reduce organic components. During the retting process, as its volume decreases, and residues are comparatively harmless, characterized of humus soil, it is filled in the land. When we see the definition of "Wastes" in Article 2, Waste Management Law, they are garbages, burnt matters, Oh-Nee, waste oil, waste acid, waste alkaline, animal corpses, and substances not required further for human life or business activity. Oh-Nee is included here in the category of waste, but the definition is not stated as a separate title and dispersed in several titles.
To explain more easily, a mixture of solid foreign materials(microbes, etc.) input or created during the purification process of fine solids (dust, etc.) mixed in sewage and waste water - 98% of water content concentrated or condensed during the purification process - is called slurry. First-dewatered slurry, 80% of water content, is called cake sludge.

Sludge production details

Sewage and wastewater include fine solids (dust, etc.) mixed during the use of water and microbic solid foreign materials input or created during the purification process. At the final stage of sewage and wastewater purification process, used is a method to separate from water the foreign materials by condensing them only normally with the input of chemicals of polymer
This condensed state is called 'Slurry'. a limp shape of 98% of water content in general (98% water, 2% solids)
This slurry is discharged separately and goes through dewatering process. Most dehydrating equipment currently installed at the sewage and wastewater treatment plant are 'belt press dewaterers' or centrifugal separation dewaterers'. A lump of final foreign materials through such dehydration process is called 'Sludge', which is normally 80% of water content (80% water, 20% solids) characteristic of watering out when holding it in the hand and pressing it.
Currently the technology of dehydration below 80% in average of water content in sludge does not exist all over the world. The reason is that we cannot draw internal water in the microbic cytoplasm, a major constituent of sludge.

Technical principle of the electric dehydrator

• To utilize "electroosmosis", one of electric inherent properties, and to utilize incidentally electro-phoresis", and "Brown motion".
• To utilize the power supply method using voltage difference, to break sludge cell membranes, and thus to discharge water in the cell

Sludge cell breaking process by electric dehydration

slurry to 70%. We contribute to sludge fuel energy business by further evolving the technology which reduces 80% cake first dehydrated to 60%.

At present our technology is introduced to domestic sewage and wastewater treatment plant and private companies for cost reduction and corporate image enhancement for improving environment. Our company is leaping toward a global environment enterprise through interchange, collaboration, and export with companies in Europe, China, USA, and Asian countries.

We are performing a leading role in true-to-the-name electric dewatering technology by securing stability, efficiency, and technique of electric dehydrators, after overcoming previous problems by rich site application experiences

Sludge treatment process of the electric dehydrator

Product specification of the electric dehydrator

Item	Contents
Kind of product	Complex type electric dehydrator (EDG-C2400)	Standard type electric dehydrator (EDG-S2400)
Product picture
Dewatered object	slurry(over 98% of water content)	sludge cake(around 80% of water content)
%of water content after dehydration	65~70%	60±3%
Optional specification	Replacement for the existing dehydrator Replacement for the new dehydrator	Secondary dehydration at the rear part of the existing dehydrator
Belt width (mm)	2,460	2,460
Treated amount (ton/hr)	8~10ton (based on 98~98% slurry)	1ton (based on 80% sludge cake)
Power consumption (kwh)	150	150
Size (LxWxH)	3510x3424x3430	3354x3510x3204
Scope of supply	Console, VAR system	Console, VAR system
Input principle	Transport slurry and coagulant through pipe with a motor, agitate in the agitator, put the slurry into the input device with a slurry head (windmill type)	Put into the sludge supply device, the sludge discharged from the first dehydrator and stored in the hopper, and supply it to the dehydrator in the fixed quantity in accordance with the sludge characteristics.

Drawing of the electric dehydrator

a. Drawing of complex type electric dehydrator(EDG-C2400)

b. Drawing of standard type electric dehydrator(EDG-S2400)

List of required power

Consumable details

* This period table may be changed according to the site conditions and user's management.
* Replacement is requested after checking the state of consumables.

Maintenance cost calculation and details

Design criteria of hydrator [Operating condition of the standard type hydrator: 8 hours]

[Design capacity based on 8~10ton/day] [based on 80% of water content]

Design criteria → Operating hour for one dehydrator is 8~10hr
For the operation of 8~10 hours/day, one dehydrator should be installed.

Maintenance cost

Calculation conditions

01 Electricity cost

[Power consumption calculation]

* Calculation basis of electricity cost
ㆍ Operating condition - dehydrator 1 set (8~10hr/day)
ㆍ Design specification - Power consumption 150kw/set
ㆍ Charge
- Basic rate 150kw x 1(set) x W6,970 = W1,045,500
- Electricity rate used 150kw x 1(set) x 8(hr/day) x W77.18= W92,616
* 2010. 08. 01. Increase of electricity rate (about 17% increase compared with that in 2008)
* Basic rate W6,970/Kw(Monthly)
* Unit rate W77.18/Kwh(average per season) Unit rate in 2008 W62.55/Kwh
* Unit rate reduced by 16% for 24 hours operation (reduction in case of night use)

02 Water capacity

* Calculation basis of water capacity - Used amount(m³) x 1(set) x 8(operating hour per day) = 8m³/day

03 Consumables and repair/maintenance costs

* Consumable costs : calculation of consumable costs
- Main consumables: Drum re-coating costs of the electric dehydrating device (W25mil./year/set)
→ Drum re-coating cost = W25,000,000/year

* Repair cost : Replacements of tools and material like filters, replaced quantity, and relevant costs
- General consumable costs : 0.5% of mechanical device costs:W2,500,000/year

Calculation details of operation cost per ton

*Excluding civil work and other utility costs

Economy of the electric dehydrator

Our dewatering technology uses electroosmosis and electrophoresis instead of physical force, allowing up to 60% of water content as it destruct sludge particles with electric action and dehydrate internal water. As dewatered sludge loses its intrinsic property and non-dry section, the following dry method can be simple and the cost will greatly be reduced for advantage. Besides, compared with existing technologies, its facility and operating costs can be reduced down to 1/2. It, as a realistic and core technology, can also be applied to pre-treatment technology to any sludge land treatment techniques

Comparison of economic feasibility for the electric dehydrator (10 ton, 80% sludge cake per day)

Economic feasibility analysis of electric dehydrator and dry system(10ton/day, 82→60% dry)