Grit Mechanism (Detritor)
Square detritor with rotating scraper and reciprocating rake classifier that settles, collects and washes grit before it can wear out pumps and fill up tanks.
Grit removal that protects everything downstream
Sand, silt and grit can wear pump impellers, erode pipes and valves and accumulate in downstream tanks. Adroit’s grit mechanism removes these heavy inorganic solids after screening and before downstream treatment, reducing abrasive wear and grit accumulation in later process units.
The system has two parts that work separately but in hydraulic step with each other: a grit settling unit, the detritor, and a grit separation unit, the classifier, which washes the organic matter off the grit before it is discharged.

Where the detritor sits in an STP
Application
The detritor is part of preliminary treatment. Screened sewage enters a square, shallow tank sized so that heavy inorganic grit settles while most of the lighter organic solids carry on with the flow. Organic matter that does settle with the grit is washed out in the classifier and returned. Taking the grit out here protects pumps, grit-sensitive mechanical equipment and tank volumes further down the line.
How the grit mechanism works
Operation
The detritor is a continuous-flow tank. Grit settles by gravity to the floor while the water flows over the outlet weir on the opposite side.
A rotating scraper mechanism sweeps the settled grit across the floor towards an opening in the side wall at the bottom of the classifier. Two or more scraper arms push the grit through this opening into the cleaning chamber.
In the classifier, a reciprocating rake drags the grit up an inclined channel. As it rises, the grit is washed, and the organic liquor drains back. The clean grit is discharged from the top through a chute for disposal. The washed organic liquor in the classifier is returned to the detritor inlet by the organic return pump or mixer.
Where grit mechanisms are used
Application areas
Municipal sewage treatment plants
Grit removal from screened sewage before primary treatment.
Sewage pumping and pre-treatment
Protects pumps and mechanical equipment from abrasive solids.
Industrial wastewater treatment plants
Removes heavy inorganic solids where grit is present.
Large inlet works
Detritor installations for high-flow municipal plants.
Why choose Adroit's grit mechanism
Features & advantages
High-torque drive
Reputed make gear drive with overload protection.
Heavy-duty drive head
Built for continuous scraping duty.
Clean grit, less organic loss
The classifier washes organic matter off the grit and returns it to the flow.
Protects the whole plant
Reduces wear on pumps and pipes, and grit build-up in tanks.
Low running cost
Low capital, operating and maintenance cost.
Grit mechanism specifications
Dimensions & manufacturing
Up to 10 m × 10 m
Detritor size
Grit settling unit (detritor) + reciprocating rake grit classifier
Main units
High-torque gear drive with overload protection
Drive
Return pump / mixer
Organic return
Mild steel, SS 304 / SS 316, or as specified
Material of construction
Frequently asked questions
FAQ
What is a detritor?
It is a square grit chamber with a rotating scraper that collects settled grit and pushes it to a classifier for washing and removal.
Why is grit removal important in an STP?
Grit is abrasive. It wears pumps, pipes and valves and settles in tanks, reducing their working volume and causing maintenance problems.
Where is the detritor installed?
In preliminary treatment, after the screens and before primary sedimentation or biological treatment.
What does the classifier do?
It separates grit from organic matter. A reciprocating rake drags the grit up an incline, washing it so that clean grit is discharged and organic liquor is returned to the flow.
How is a grit mechanism sized?
From the design and peak flow, the grit load, the settling criteria and the chamber size.
Brochures, datasheets & media
Downloads
Documents
files
Photos
photos
Videos
videos
Explore more solutions
Related technologies
Chain Flight Sludge Scraper
Continuous sludge and scum collection for rectangular settling tanks, driven slowly and steadily by heavy-duty chains.
Clarifier
Scraper mechanisms for circular primary and secondary clarifiers, with bridge and drive arrangements matched to tank size.
Clariflocculator
Flocculation and clarification in one circular tank, designed to CPHEEO guidelines, in full bridge, half bridge, central and peripheral drive versions up to 60 m diameter.
Need fine screening sized for your inlet works?
Send us your flow rate, channel dimensions and the fine-solids you need to capture — our engineers will recommend the right Stepflow configuration.
Call us
+91 70248-48383Email
[email protected]
Enquire about Grit Mechanism (Detritor)
Product enquiry
Tell us about your requirement and we’ll respond with specifications, references and pricing.
Request a quotation
Fields marked * are required. We typically respond within one business day.
(() => {
if (window.adroitEnquiryButtonsReady) return;
window.adroitEnquiryButtonsReady = true;
const rootSelector = ".adroit-contact-form";
const buttonSelector = [
"#wsf-1-field-38",
"#wsf-1-field-39",
].join(", ");
const values = {
"wsf-1-field-38": "Product Enquiry",
"wsf-1-field-39": "Service Request",
};
function getFormRoot(element) {
return element.closest(rootSelector);
}
function getHiddenField(form) {
let field = form.querySelector(
'input[data-enquiry-type-field="true"]'
);
if (!field) {
field = document.createElement("input");
field.type = "hidden";
field.name = "inquiry_type";
field.dataset.enquiryTypeField = "true";
form.appendChild(field);
}
return field;
}
function getErrorRow(formRoot) {
let errorRow = formRoot.querySelector(
'[data-enquiry-error-row="true"]'
);
if (errorRow) return errorRow;
const fieldsGrid = formRoot.querySelector(".wsf-fields");
const firstField = formRoot.querySelector(
"#wsf-1-field-wrapper-20"
);
if (!fieldsGrid || !firstField) return null;
errorRow = document.createElement("div");
errorRow.className =
"wsf-extra-small-12 wsf-tile wsf-field-wrapper";
errorRow.dataset.enquiryErrorRow = "true";
errorRow.hidden = true;
const errorMessage = document.createElement("div");
errorMessage.className = "wsf-invalid-feedback";
errorMessage.textContent = "This field is required.";
errorMessage.setAttribute("aria-live", "polite");
errorRow.appendChild(errorMessage);
fieldsGrid.insertBefore(errorRow, firstField);
return errorRow;
}
function showError(formRoot) {
const errorRow = getErrorRow(formRoot);
if (!errorRow) return;
errorRow.hidden = false;
const errorMessage = errorRow.querySelector(
".wsf-invalid-feedback"
);
if (errorMessage) {
errorMessage.style.display = "block";
}
formRoot.querySelectorAll(buttonSelector).forEach((button) => {
button.classList.add("is-invalid");
button.setAttribute("aria-invalid", "true");
});
}
function clearError(formRoot) {
const errorRow = formRoot.querySelector(
'[data-enquiry-error-row="true"]'
);
if (errorRow) {
errorRow.hidden = true;
}
formRoot.querySelectorAll(buttonSelector).forEach((button) => {
button.classList.remove("is-invalid");
button.removeAttribute("aria-invalid");
});
}
function hasSelection(formRoot) {
return Boolean(
formRoot.querySelector(
"#wsf-1-field-38.is-selected, #wsf-1-field-39.is-selected"
)
);
}
function validateEnquiry(formRoot) {
if (hasSelection(formRoot)) {
clearError(formRoot);
return true;
}
showError(formRoot);
return false;
}
function selectButton(button) {
const formRoot = getFormRoot(button);
const form = button.closest("form");
if (!formRoot || !form) return;
formRoot.querySelectorAll(buttonSelector).forEach((item) => {
const isSelected = item === button;
item.classList.toggle("is-selected", isSelected);
item.setAttribute("aria-pressed", String(isSelected));
});
getHiddenField(form).value = values[button.id] || "";
clearError(formRoot);
}
/*
* Window capture runs before WS Form's button click handler.
* This stops WS Form AJAX submission only when enquiry type is missing.
*/
window.addEventListener(
"click",
(event) => {
const enquiryButton = event.target.closest(
`${rootSelector} #wsf-1-field-38, ${rootSelector} #wsf-1-field-39`
);
if (enquiryButton) {
selectButton(enquiryButton);
return;
}
const submitButton = event.target.closest(
`${rootSelector} button[type="submit"], ${rootSelector} input[type="submit"]`
);
if (!submitButton) return;
const formRoot = getFormRoot(submitButton);
if (!formRoot) return;
if (validateEnquiry(formRoot)) return;
event.preventDefault();
event.stopImmediatePropagation();
},
true
);
/*
* Covers pressing Enter in a form field.
*/
window.addEventListener(
"submit",
(event) => {
const form = event.target;
if (!(form instanceof HTMLFormElement)) return;
const formRoot = getFormRoot(form);
if (!formRoot) return;
if (validateEnquiry(formRoot)) return;
event.preventDefault();
event.stopImmediatePropagation();
},
true
);
function initialize() {
document.querySelectorAll(rootSelector).forEach((formRoot) => {
const form = formRoot.querySelector("form");
formRoot.querySelectorAll(buttonSelector).forEach((button) => {
button.classList.remove("is-selected", "is-invalid");
button.removeAttribute("aria-invalid");
button.setAttribute("aria-pressed", "false");
});
clearError(formRoot);
if (form) {
getHiddenField(form).value = "";
}
});
}
if (document.readyState === "loading") {
document.addEventListener("DOMContentLoaded", initialize, {
once: true,
});
} else {
initialize();
}
})();