science

Lava filter

Lava filter is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lava filter rather than just read about it. In short: A lava filter is a biological filter that uses lavastone pebbles as support material on which microorganisms can grow in a thin biofilm. This community of microorganisms, known as the periphyton, break down the odor components in the air, such as hydrogen sulfide.

Key takeaways

Lava filter belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lava filter to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lava filter from memory before moving on to harder problems.

Reference excerpt

A lava filter is a biological filter that uses lavastone pebbles as support material on which microorganisms can grow in a thin biofilm. This community of microorganisms, known as the periphyton, break down the odor components in the air, such as hydrogen sulfide. The biodegradation processes that occurs is provided by the bacteria themselves. In order for this to work, sufficient oxygen as well as water and nutrients (for cell growth) is to be supplied.

Method Contaminated air enters the system at the bottom of the filter and passes in an upward direction through the filter. Water is supplied through the surface of the biofilter and trickles down over the lava rock to the bottom, where it is collected. Constant water provisioning at the surface prevents dry-out of the active bacteria in the biofilm and ensures a constant pH value in the filter. It also functions to make nutrients available to the bacteria.

Percolating water collected at the filter bottom contains odour components as well as sulfuric acid from the biological oxidation of hydrogen sulfide. Depending on the process design the collected water is recirculated or subjected to further treatment.

Types of systems At present: 2 types of systems are used;

constantly submerged lava filters (for treatment ponds, combined treatment ponds/irrigation reservoirs, ...) not-submerged lava filters (for wastewater treatment; wastewater is simply sprayed on the pebbles with this system)

Constantly submerged lavafilters These are constructed out of 2 layers of lava pebbles and a top layer of nutrient-free soil (only at the plants roots). On top, water-purifying plants (as Iris pseudacorus and Sparganium erectum) are placed. Usually, around 1/4 of the dimension of lavastone is required to purify the water and just like slow sand filters, a series of herringbone drains are placed (with lava filters these are placed at the bottom layer). The water-purifying plants used with constantly submerged, planted, lavafilters (e.g. treatment ponds, self-purifying irrigation reservoirs, ...) include a wide variety of plants, depending on the local climate and geographical location. Plants are usually chosen which are indigenous in that location for environmental reasons and optimum workings of the system. In addition to water-purifying (de-nutrifying) plants, plants that supply oxygen, and shade are also added in ecologic water catchments, ponds, ... This to allow a complete ecosystem to form. Finally, in addition to plants, locally grown bacteria and non-predatory fish are also added to eliminate pests. The bacteria are usually grown locally by submerging straw in water and allowing it to form bacteria (arriving from the surrounding atmosphere). The plants used (placed on an area 1/4 of the water mass) are divided in 4 separate water depth-zones; knowingly:

A water-depth zone from 0–20 cm; Iris pseudacorus, Sparganium erectum, ... may be placed here (temperate climates) A water-depth zone from 40–60 cm; Stratiotes aloides, Hydrocharis morsus-ranae, ... may be placed here (temperate climates) A water-depth zone from 60–120 cm; Nymphea alba, ... may be placed here (temperate climates) A submerged water-depth zone; Myriophyllum spicatum, ... may be placed here (temperate climates) Finally, three types of (non-predatory) fish (surface; bottom and ground-swimmers) are chosen. This of course to ensure that the fish may 'get along'. Examples of the three types of fish (for temperate climates) are:

Surface swimming fish: Leuciscus leuciscus, Leuciscus idus, Scardinius erythrophthalmus Middle-swimmers: Rutilus rutilus Bottom-swimming fish: Tinca tinca

See also Constructed wetland Treatment pond Organisms used in water purification

References

Illustrations

Worked examples

Example 1 — a first encounter with Lava filter

Start with the simplest possible case. Write down what Lava filter claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lava filter before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lava filter ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lava filter

In research: Lava filter appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lava filter in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lava filter is common in secondary-school and first-year university syllabi. It links to neighbouring topics Appropriate technology, DIY culture, Environmental soil science, so understanding it makes those chapters shorter.
In everyday life: Look for Lava filter outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lava filter in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lava filter means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lava filter out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lava filter in simple terms?

Why does Lava filter matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lava filter?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lava filter.