TSS. This method quantifies solids in water or wastewater samples using gravimetric analysis following oven drying. Solids refer to matter suspended or dissolved in the water or wastewater and may affect water or effluent quality in adverse ways. The method has a detection limit of approximately 4 mg/L for TSS and 10 mg/L for TDS, TS and VSS. The results are generally reproducible within 10%.