HDPE Covered Lagoons for Biogas Capturing

Per m or per m²?

Tqvm PW , I estimated the force acting below the membrane to the total area. Than it with the circumference. It is kg force per meter.

First, I'd look for someone with adequate education, knowledge and experience who can evaluate a design proposal for a HDPE Covered Lagoons.

It doesn't sound like you are that person.

Yes Lyn I agree with you. I am know nothing about membrane design .

Q1: "How well does the design proposal fit the specification?"

Q2: "Given the areas where there is a misfit, what discussions and adjustments need to be made to reduce the misfit?"

Q3: "How well does the proposal fit the intended Return On Capital Employed criteria? Is it a go-er?"

The cost of investment is not an issue. The lagoon area 60m x 30 m at biogas pressure 4 mili barg.

The questions are for internal consumption, not for CR4. Commercially sensitive stuff doesn't really warrant a look-in here on the basis of business confidentiality.

Did you consider the weight of rain water on top of the covering ?

10 mm of rain will be 18 cubic meter and it will sag through in the center.

And the span of 60mx30m means some type of support will be required in any event.

There is much to consider here, that's why an on-site consultant is required.

Put a 30 cm sand layer on top. Put drainage pipe under the HDPE foil.

What is this with the unit mass per meter?

HDPE 60 mil Thickness at 1.448 kg per sq.m.

If the 30 cm sand layer on top than the rain water ( I assume ) drainage pipes should be over the HDPE foil.

And how do you capture the biogas?

Sure drainage over the foil might be beneficial, but in sand it drains away anyway doesn't it?

You are going to have to seal the membrane at the sides and stop leakage so you will need a ring beam around the perimeter of the lagoon. Something like reinforced concrete 200mm wide and 1m deep. Given that your ground conditions will be poor, will the ground support 6 t/m² for the beam?

I have seen 30m span water reservoirs covered with an aluminum roof supported by two tensioned wires, held apart with vertical spreaders to create lightweight trusses. By making the spreaders longer in the center you can form a curved upper surface that will shed rainwater to the sides. Cast deep gullies into your beams to duct the water away or it will wash our your foundations. You will need trusses every 3/5m along the 60m length and the side beam will need to take the side loading created by the wire tension.

The top wire will need to be covered so that your membrane can slide over it without ripping. I would also suggest two membranes with a small amount of pressurised air between, say 1psi. If the pressure falls the top membrane is damaged. If the pressure rises the bottom membrane is damaged. This gives you time for repairs before you play fireworks with a very large quantity of gas.

TQVM for all the inputs. The bio gas potential for palm oil mills are huge. I we look at the picture attached and pls help me 1) Do we need worry about the rain water ? Do we need any lightweight trusses?

In your original post I assumed that you were collecting gas formed in accumulated debris in the bed of the lagoon. You have not been specific about how the gas you are collecting is produced.

Yes you need to worry about the rain water. Palm oil plants only produce a commercial yield in high rainfall areas. You are covering 1800m² of rainfall catchment area and concentrating all the rain into two 60m long strips at each side of the lagoon.

Palm oil only grows well in deep permeable soil. If the gas cannot find a release through your membrane it will permeate through the soil and leak away. Thus the need for a ring beam.

You may not need trusses to support the membrane but they will stop the the structure flapping about and flaying itself to pieces in high winds (monsoons or typhoons).

Until this snippet, there was very little to go on. The thread now seems to be wandering away from how-to-evaluate-a-proposal and into how-to-design-an-installation. If this is true, then securing the services of an experienced local Consultant is the way forward.

Trying to get it designed by a bunch of anonymous strangers over the internet in a public Engineering forum just isn't the way to go.