O biofiltro recebe água da bomba d'água.

Recebe is the 3rd person singular form of the verb receber in the present indicative.

• receber = to receive
• recebe = receives / does receive

It is recebe because the subject is o biofiltro, which is singular:

• O biofiltro recebe água. = The biofilter receives water.

In technical descriptions, Portuguese often uses the present tense to explain how a system works in general.

O is the masculine singular definite article, meaning the.

So:

• o biofiltro = the biofilter

The noun biofiltro is masculine, so it takes o, not a.

This usually means we are talking about a specific biofilter, or about the biofilter as a known part of a system. If it were nonspecific, you might see:

• um biofiltro = a biofilter

In Portuguese, mass nouns like água often appear without an article when speaking in a general sense.

So:

• recebe água = receives water

This is very natural.

If you say recebe a água, it usually means receives the water, meaning specific water already identified in the context.

So the difference is roughly:

• recebe água = receives water
• recebe a água = receives the water

Da is a contraction of:

• de + a = da

Here, de expresses source or origin, so da bomba d'água means from the water pump.

So:

• água da bomba d'água = water from the water pump

A very important point: de does not always mean just of. Depending on context, it can mean of, from, about, and more. In this sentence, from is the best understanding.

Because bomba d'água is being treated as a specific noun phrase with the article a:

• a bomba d'água = the water pump

When de combines with a, you get:

• de + a = da

So:

• água da bomba d'água = water from the water pump

If you wanted to say from a water pump, you would say:

• água de uma bomba d'água

Yes, bomba can mean both bomb and pump. The meaning depends on context.

In a mechanical or plumbing context:

• bomba d'água = water pump

In another context:

• bomba = bomb

So in this sentence, because we are talking about water moving through a system, bomba clearly means pump.

D'água is a reduced form of de água that commonly appears in certain fixed expressions and compound terms.

So:

• bomba d'água = water pump

This is a very common set expression in Brazilian Portuguese.

For a learner, the safest way to think about it is:

• d'água often appears in established names or compounds
• de água is the more general, transparent form

So you should learn bomba d'água as a chunk.

Because the two instances of água are doing different jobs.

1. The first água is the actual thing being received:

   • recebe água = receives water

2. The second água is part of the compound noun:

   • bomba d'água = water pump

So the sentence is not repetitive in a strange way. It is saying that the biofilter receives water, and that this water comes from the water pump.

Yes, biofiltro is normally written as one word.

It is a compound formed with the element bio- plus filtro:

• bio = life / biological
• filtro = filter

Portuguese often writes this kind of technical term as a single word:

• biofiltro
• biologia
• biocombustível

So biofiltro is just the standard noun here.

A simple learner-friendly approximation is:

O biofiltro recebe água da bomba d'água.
oo bee-oh-FEEL-troo heh-SEH-bi AH-gwah da BOM-ba DA-gwah

A few notes:

• recebe is often pronounced something like heh-SEH-bi in Brazil
• água sounds like AH-gwah
• d'água links smoothly and sounds roughly like DA-gwah
• r in biofiltro is not the English r; it is usually a light tapped sound in Brazilian Portuguese

Yes, a few small variations are possible depending on style and context.

For example:

• O biofiltro recebe a água da bomba d'água.
  This sounds more like the biofilter receives the water from the water pump, with more emphasis on specific water.

• O biofiltro recebe água de uma bomba d'água.
  This means the biofilter receives water from a water pump, with a nonspecific pump.

• Água da bomba d'água é recebida pelo biofiltro.
  This is more formal and passive: Water from the water pump is received by the biofilter.

The original sentence is natural and straightforward for describing how a system works.