{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.slow-sand-filter","code":"thing-q2608039","url":"https://ver.cy/models/thing/q2608039/","name":"slow sand filter","alternateNames":[],"kind":"thing","status":"published","version":"0.2.0-wave.4","language":"en","classifiers":{"family":"Thing Registry","category":"Physical world and living systems","entryKind":"thing","plane":"PHY","domain":["PHY.BLT"],"industry":[],"navPath":"","tags":[],"facets":{}},"whatItIs":"A water treatment filter in which raw water flows slowly downward through a bed of fine sand, where a biological layer called the schmutzdecke forms on the surface and removes pathogens and organic matter through biological, physical and chemical processes, first used for public supply by James Simpson for the Chelsea Waterworks Company in London in 1829, still valued for small communities because it needs no chemicals and little energy, though it requires land and periodic scraping.","purpose":"Let an agent explain slow sand filters, relay principles, design, performance and maintenance from water engineering and WHO sources, and distinguish slow sand filters from rapid sand filters, biosand household filters, membrane filtration and chlorination, noting that treated water quality must be verified and boil water advisories followed.","scope":{"in":[],"out":[],"boundaries":[]},"distinguishingFeatures":["Biological layer","No chemicals","Slow flow","Land intensive"],"structure":{"bundles":[{"id":"understand","name":"Understand","description":"What a slow sand filter is.","layers":[{"id":"definition","name":"Definition","description":"Definition.","findings":[{"id":"definition-finding","name":"Definition","description":"Definition.","questions":[{"text":"What is a slow sand filter, and how does it differ from rapid sand filters, biosand filters, membranes and chlorination?","kind":"definition"},{"text":"Is there a boil water advisory or doubt about water safety, in which case follow local authority advice?","kind":"boundary"}]}]},{"id":"biology","name":"Schmutzdecke","description":"Biological layer.","findings":[{"id":"biology-finding","name":"Schmutzdecke","description":"Schmutzdecke.","questions":[{"text":"What is the schmutzdecke and how does it remove pathogens?","kind":"definition"},{"text":"Which entry fits biofilm?","kind":"action"}]}]}]},{"id":"design","name":"Design","description":"Design.","layers":[{"id":"sizing","name":"Sizing","description":"Sizing.","findings":[{"id":"sizing-finding","name":"Sizing","description":"Sizing.","questions":[{"text":"How are filter area, sand size and flow rate chosen?","kind":"measurement"},{"text":"Which references are standard?","kind":"provenance"}]}]},{"id":"maintenance","name":"Maintenance","description":"Maintenance.","findings":[{"id":"maintenance-finding","name":"Maintenance","description":"Maintenance.","questions":[{"text":"How are filters scraped and resanded?","kind":"provenance"},{"text":"Which sources are cited?","kind":"provenance"}]}]}]},{"id":"performance","name":"Performance","description":"Performance.","layers":[{"id":"removal","name":"Removal","description":"Pathogen removal.","findings":[{"id":"removal-finding","name":"Removal","description":"Removal.","questions":[{"text":"How effective are slow sand filters, and what extra disinfection is recommended?","kind":"provenance"},{"text":"Which entry fits water disinfection?","kind":"action"}]}]},{"id":"standards","name":"Standards","description":"Standards.","findings":[{"id":"standards-finding","name":"Standards","description":"Standards.","questions":[{"text":"What do WHO guidelines say about multi-barrier treatment?","kind":"provenance"},{"text":"Which entry fits WHO Guidelines for Drinking-water Quality?","kind":"action"}]}]}]},{"id":"context","name":"Context","description":"History and development.","layers":[{"id":"history","name":"History","description":"History.","findings":[{"id":"history-finding","name":"History","description":"History.","questions":[{"text":"How did slow sand filtration help control cholera, as in Hamburg and Altona in 1892?","kind":"provenance"},{"text":"Which entry fits 1892 Hamburg cholera epidemic?","kind":"action"}]}]},{"id":"development","name":"Development","description":"Small communities.","findings":[{"id":"development-finding","name":"Development","description":"Development.","questions":[{"text":"Why are slow sand filters suited to low-resource settings?","kind":"provenance"},{"text":"Which entry fits WASH?","kind":"action"}]}]}]}]},"agentConduct":{"may":["Monitor flow, head loss and water quality of a slow sand filter for its operator.","Report when a filter needs its surface layer scraped or its sand replaced."],"mustNot":["Send water to supply from a filter whose biological layer has not matured, without other treatment.","Raise flow rates beyond the design so that pathogens pass through.","Change settings on a public water treatment plant it is not authorized to operate.","Hide test results that show the filter is failing."],"requiresHuman":["Taking a filter out of service or returning it to supply.","Issuing or lifting a boil-water notice."]},"ethics":{"considerations":["Drinking water safety depends on the filter working; failure can make whole communities ill.","Slow sand filters are a low-cost choice for poorer communities, so their reliability matters for equity."],"affectedParties":["People drinking the water","Plant operators","Communities served"]},"owners":{"steward":"The water utility or community that operates the filter, under the drinking water regulator.","roles":[],"masterSystems":[]},"relations":[{"target":"Q7973769","type":"parent","note":"registry parent class"},{"target":"water filter","type":"related","note":"in general terms"},{"target":"schmutzdecke","type":"related"},{"target":"water treatment","type":"related"},{"target":"rapid sand filter","type":"related"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.slow-sand-filter","Wikidata: Q2608039 (https://www.wikidata.org/wiki/Q2608039)"]},"properties":{"applicability":"required","items":["filtration rate: about 0.1-0.4 m/h","first public supply use: 1829 year - Chelsea Waterworks","pathogen removal: high for bacteria and protozoa when mature note"]},"recognition":{"applicability":"required","items":["Biological sand filter for water treatment","Slow sand filter, schmutzdecke","Rapid sand filters use coagulation and backwashing; biosand filters are household units; membranes use pores; chlorination disinfects chemically","Large open or covered basins filled with sand beneath a layer of water."]},"capabilities":{"applicability":"required","items":["explain principles","relay design and maintenance","describe performance","distinguish related treatments"]},"hazards":{"applicability":"required","items":["Reduced performance before the biological layer matures","Clogging with turbid water","Assuming untested water is safe"]},"interfaces":{"applicability":"required","items":["WHO Guidelines for Drinking-water Quality","National drinking water regulations"]},"context":{"applicability":"required","items":["Treating drinking water.","municipal slow sand filters","community filters","riverbank filtration as related","household biosand filters"]}},"sources":[{"title":"Wikidata item Q2608039: slow sand filter","url":"https://www.wikidata.org/wiki/Q2608039","note":"identity and sense of the item"},{"title":"Wikipedia: Slow sand filter","url":"https://en.wikipedia.org/wiki/Slow_sand_filter","note":"general description of the item"}],"openQuestions":["Should the schmutzdecke be a separate entry?","How should water engineering sources be linked?","How should household biosand filters be linked?"],"resources":{"spec":"/models/things/publications/thing-q2608039/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q2608039/spec.json"],"providers":["Claude"],"researchStatus":"unreviewed","generatedAt":"2026-09-13T20:23:43Z","builder":"tools/build_cards.py@1.0.0"},"completeness":{"sections":{"classifiers":"filled","whatItIs":"filled","purpose":"filled","distinguishingFeatures":"filled","structure":"filled","agentConduct":"filled","ethics":"filled","owners":"filled","relations":"filled","interaction.identity":"filled","interaction.properties":"filled","interaction.recognition":"filled","interaction.capabilities":"filled","interaction.hazards":"filled","interaction.interfaces":"filled","interaction.context":"filled","sources":"filled"},"notes":{"_gate":"Published through the thing publication gate 1.0 on 2026-10-06T19:51:58+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}