A vermifilter system for reducing nutrients and organic-strength of dairy wastewater

Vermifiltration is an emerging low-cost and environmentally sustainable technology for the treatment of wastewater and recovery of nutrients. This study evaluated, for six months, the efficacy of a pilot-scale vermifilter for the treatment of a side-stream of dairy wastewater at a commercial dairy farm in Washington State. Samples of dairy wastewater were collected at the upstream and downstream of the vermifilter during these six months and analyzed for reductions in the solids contents (total solids (TS) and total suspended solids (TSS)), chemical oxygen demand (COD), pertinent nitrogen species (total nitrogen (TN), total ammonia-nitrogen (TAN), nitrate-nitrogen (NO3–N), and phosphorus species (total phosphorus (TP) and orthophosphate (Ortho-P)). The respective reductions were 81 ± 7.1% for TAN, 77 ± 8.4% for TN, and 74 ± 9.5% for NO3–N. Total solids reduction was, generally, low at 21 ± 7.0% but the reduction of TSS was significantly high at 68 ± 10%. Results indicated modest reductions of TP (48 ± 6.0%) and COD (45 ± 4.1%) but relatively lower Ortho-P reduction (3.9 ± 19.2%). Regression modeling showed that ambient temperature has a significant influence on the reduction efficiencies of TAN (by as much as 50%) and COD (by as much as 59%). Overall, this study demonstrated that vermifiltration has great potential in alleviating nutrients contents and simultaneously reducing the organic strength of the vermifilter effluents. [Display omitted] •The system significantly reduced N-species (TN = 77%; TAN = 81%; 74% = NO3−-N).•Temperature significantly impacted reductions of TAN (by ∼50%) and COD (by ∼59%).•Reductions of COD, NO3-N, and Ortho-P were dependent on their inlet concentrations.•The system produced suitable water reusable for flushing manure from the barns.•The system effluent is irrigatable on nearby land base as it has less nutrients.