Manure Liquid - Solids Separation
Prepared by:
James C. Barker
Professor and Extension Specialist
Biological and
Agricultural Engineering
North Carolina State University, Raleigh, NC
Published by: North Carolina Cooperative Extension
Service
Publication Number: EBAE 182-93
Last Electronic Revision: March 1996 (JWM)
Lagoon management is eased by separating solids from raw manure or flushed
waste prior to lagoon input. Removing fiber from cattle wastes and grit from
poultry manure significantly reduces the lagoon solids buildup rate and
associated pumping problems. Removal of oxygen-demanding solids in swine and
poultry manure reduces the lagoon organic loading and lessens its odor
potential. Beneficial uses of the recovered solids include bedding
materials, animal feed ration supplements, composts, and soil amendments.
MECHANICAL
To recover a drier by-product relative to other methods, vibrating-screen,
sloping stationary screen or pressure-roller mechanical separators are
probably most advantageous. Waste is collected in a sump sized to store 3 - 4
days accumulation of manure plus dilution and flush water. A submersible or
stationary bottom-impeller, agitator-lift pump mixes the waste into a slurry
and pumps it across the separator where the liquid drains into the lagoon.
Solids are dry enough to be handled by conventional solid materials handling
equipment. Up to 30% of the total solids and 25% of the oxygen-demanding
materials are removed.
GRAVITY
A gravity settling basin may be less costly while removing 50% or more of the
solids from liquid manure. Solids can be settled and filtered by a shallow
basin (2 - 3 feet deep) with concrete floor and walls and a porous dam or
perforated pipe outlet. It should allow access by a front-end loader to
remove solids every 1 - 2 months.
An alternative is an earthen settling basin for 6 to 12 months storage of
solids. The basin top width should be no more than 100 feet with a length-to-width
ratio near 3:1 and a liquid depth of 8 - 10 feet. The basin
contents should be thoroughly agitated and removed for land spreading either
by liquid manure spreader or slurry irrigation.
A third alternative consists of a large rectangular metallic or concrete
settling tank with a 3:1 length-to-width ratio and an 8-feet liquid depth.
Tank volume depends on a peak-flow wastewater detention time of 10 to 30
minutes. Most readily settleable solids in livestock manure settle in about
10 minutes although some additional settling occurs for hours. Tank inlets
and outlets are baffled and solids are removed by automated skimmers and
scrapers. Unless substantial solids storage is added to the settling tank
volume, cleanouts will need to occur frequently.
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people
regardless of race, color, national origin, sex, age, or disability. North
Carolina State University, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.
EBAE 182-93
Back up one