Método

The effluent treatment system will include two main parts, the anaerobic section and aerobic stabilisation process before the final discharge of treated palm oil mill effluent onto the plantation for palm tree irrigation.

The condensate discharge from the sterilizers is pumped to the post static clarifier an oil recovery system tank.

The oil skimmers removes the highly contaminated oil from both the clarifier and sludge decanter tank which is isolated in a special drumming holding tank.

The sludge will than pass through a CAF unit for the removal of disolved oils, grease by flotation process etc,… before being fed to the cooling pond.

Every precaution is to be taken to ensure that this oil cannot and does not contaminate the crude oil system.

The objective is to reduce the loading of the effluent treatment system by the removal of the oil and solid matter in sterilizer condensate at an early stage.

The deoiled sterilizer condensate is then discharged in to its own isolated effluent collection pit And overflow to the effluent treatment sys tem.

The sludge slurry which are drained from the static clarifier and sludge decanter tank are discharged to the drying bed or conveyed to the rotary sludge dryer for the drying process.

The anaerobic phase is favoured by higher temperature and the absence of air.

The influent from the sterilizer sludge pit and the clarification pit is to be pumped to the cooling pond and than to the mixing pond.

The anaerobic process start to take place in the first pond and end at the digester tanks.

There the complex organic materials are first solubilized by the extra cellular enzymes and then converted to volatile acids by acid producing bacteria.

In the last methane fermentation phase the volatile acids are transformed to methane and carbon dioxide.

The process is to be accelerated by the circulation of the bacteria laden sludge into the mixing pond of the material from the last digester tank.

The acidification process will have an HRT of 1 day. Effluent from the mixing pond is pumped from the collecting sump and into the digesters with a total HRT of more than 20 days.

The discharge from the overflow of the final anaerobic tank is to be discharge into an open pit and pumped into the aerobic reactor tanks for the extended aeration process equipped with over powered mechanical aerators.

The overflow of the aerobic reactor tank, operating in tandem with a total HRT of 4 days will be pumped to the clarifier tank for the removal of solids.

The sludge scum is to be held back and removed from the ample sized “sludge clarification tank”.

Sludge accumulated at the bottom of the clarifier, and drying bed, are to be removed by the auto programmed system provided for the sludge removal process.

The separated sludge cake can be dried in rotary dryer and used as plant nutrient in compound form as a by product.

The treated effluent is now pumped to the final effluent holding tank.

A finish effluent holding tank will hold the effluent waste water with a BOD of 20 ppm for displacement into furrows in the plantation disposal area.

The system is to be stable and is to be capable of with standing reasonable shock loads.

The efficiency of the system is facilitated by a monitoring and programmable control system design which requires only simple maintenance and operational skills.

4.4 DISPOSAL OF TREATED EFFLUENT FOR LAND APPLICATION.

The recycling of POME in plantations is now widely accepted as an economically viable and environmentally acceptable waste management technique.

Treated Effluent are pumped or discharged by gravity to the pre-selected area as a good source of plant nutrients and a value added ( RM 350 per ha / year ) cost effective organic fertilizer.

The disposal of treated effluent for land application require an area of approximately 69 hectares in the plantation, have been marked in the vicinity of the proposed oil palm mill to receive the effluent in loaded furrows.

A typical furrow layout is shown in the report drawing section.

Field drains on the sides of each plot which act as trenches to prevent poaching.

a. Methods of Land Application.

The percolation through furrows or trenches method will be used in the land application of treated effluent of approximately 560m3 / day / ha for the given volume at an application cycle of mor e than 90 days, based on experience.

b. Factors for consideration.

The following factors effect the rate of application.

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Soil characteristics such as porosity, water table, acidity of soil;

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Characteristics of effluent, such as concentration of large solids;

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Age of oil palms;

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Vegetation in between the oil palms;

Over application of the effluent must be avoided which may result in anaerobic conditions in the soil by formation of an impervious coat of organic matter on the soil surface.

c. The percolation through furrows or trenches system.

Waste Water Effluent is pumped or discharged by gravity to the high points of the pre-selected area and allowed to drain down the slopes in furrows or trenches shown in the appendix “ Typical Furrow layout”.

The velocity of flow is given as a steady infiltration rate of 7 – 11 cm per hour, slow enough to enable percolation into the soil and also it prevents erosion.

An area of approximately 110 hectares have been marked and allocated in the vicinity of the proposed oil palm mill, shown in the “ Soil suitability for land application of Palm Oil Mill Effluent Survey Report” enclosed.

The furrows or trenches are about 90 cm / 60 width x 75 cm depth shown in the appendix and survey report.

Field drains of each plot, which act as pits to prevent poaching and used as silt traps to contain sediments transported by surface erosion.

d. Effects of land application.

Yields of oil palm increases with the use of oil palm mill effluent. The optimum rate of application is approximately 40 cm rainfall per year.

The nutrient value of the soil also shows improvements with land application, especially the nitrogen, phosphorus, potassium and magnesium values.

The effect on underground water and surface drainage, are negligible.

4.5 CONTROL OF AIR EMISSIONS.

The Environmental quality ( clean air ) regulation 1978 stipulate the permitted level of solids concentration in gases emitted from solid waste thermal plants to be not more than 0.4 g per

cubit meter.

Air emissions from oil palm mills are from the boilers and incinerators, being mainly gases with particulates such as tar and soot droplets of 20 – 100 microns and a dust load of about 3000 to 4000 mg. / NM3.

Incomplete combustion of the boiler and incinerator produces dark smoke resulting from burning of a mixture of solid waste fuel such as shell, fibre and some times empty bunches.

A good design and properly rated boiler capacity with a closed loop control over the fuel feed rate and air supply will ensure steady state combustion in tandem with steam demand.

The introduction of the proposed system will alter the situation whereby the thermal plant such as the waste fuel boiler shall emit clean smoke in accordance to the DOE standard requirements.

In document UNIVERSIDAD COMPLUTENSE DE MADRID (página 123-130)