This study evaluated and compared the effectiveness and economic costs of a polyacrylamide (PAM) assisted continuous gravity belt thickener and a PAM assisted inclined stationary gravity screen separator equipped with a backwash spraybar, each in tandem with an inclined stationary gravity screen-roll press separator to separate the solid and liquid components of liquid swine manure (raw slurry) under production scale operating conditions. The separation systems were operated from June through December processing 7,222,725 L (1,908,048 gal) of raw untreated slurry (RS1). Both treatments, gravity belt thickener and gravity screen, showed significant reductions of 84.9% and 97.8% for Settleable Solids, 93.2% and 93.7% for Total Suspended Solids, 63.7% and 69.5% for Chemical Oxygen Demand, 23.3% and 31.8% for total Nitrogen, and 52.3% and 60.5% for total Phosphorus, respectively, in the treated effluent. The cost for separation with the gravity belt thickener system was 0.474 per L (1.791 per gal) of raw slurry. The separation cost for the gravity screen system was 0.402 per L (1.518 per gal) of raw slurry. Application costs for irrigating the separated effluent generated from either system added another 0.061 per L (0.234  per gal) of raw slurry. Either of these solid liquid separation systems would be an effective and economically viable alternative to current disposal methods while providing additional operational and environmental benefits.