Septic systems are wastewaters treatment units for onsite storage or partial treatment of domestic wastewaters. A typical septic tank contains scum (the substances floating on the top, e.g. fats, oil, grease or any other floating matter), sludge (i.e. solids sedimented on the bottom of the septic tank) and effluent (semi-treated wastewater which fills the most part of the septic tank). Most of the pathogens contained in the effluent and sludge die within 2-3 months, a substantial concentration remains due to the continuous inflow of the blackwater fraction from the toilet facilities. Furthermore, the effluent and septic sludge may potentially contain pharmaceuticals, endocrine disruptors or surfactant substances from house cleaning or personal care products as well as high concentration of organic compounds and nutrients (N and P). Those contaminants can pollute both surface water and groundwater resources once the effluent and the septic sludge are finally disposed of in the environment. The application of appropriate treatment and reuse approaches may prevent or reduce pollution of the water resources. Based on a technology review study by Singh et al. (2017) and Krysnasamy et al. (2013), and a recent research on lactic acid fermentation of fecal sludge from EcoSan systems (Andreev, 2017), a demonstration model was designed and developed in this study, which applies the concept of lactic acid fermentation and vermifiltration for treatment of effluent and sludge from septic tanks. The model, which runs on a batch mode, consists of various components including: 1) a 1000 L capacity septic tank with a buffle wall to allow settling of solids, and prevent plugging of the inlet pipe by the scum layer; 2) a one-compartment vermifilter a vermibed and matrix of biochar, pebble and gravel. The biochar layer traps the solids and nutrients as well as reduces the odour, the pebble and gravel has an additional treatment role for removing of remaining organic matter, N and P and preventing of clogging of the system; 3) collector for the treated effluent and 4) an irrigation system that is fed by the vermifilter effluent. In order to have the system functioning all year around, the elements 2-4 are placed in a greenhouse. The water from the septic tank flows into an equaliser, then pumped to the second reservoir (located above the vermifilter), from where via gravitation flows into the vermifilter. For the primary treatment of the effluent and sludge, a multi-strains lactic acid bacteria culture (LAB) (Lactobacillus, Leuconostoc, Pediococcus, Bacillus sp.) obtained from sauerkraut fermentation, at a ratio of 1 L per 50 L of wastewater (Andreev, 2017) will be added to the septic tank. LAB culture addition will contribute as antimicrobial against to the pathogens (Alepu Odey, 2018), reduction of COD and odour as well as sludge solubilization (Lee et al., 2008). The density of earthworms added to the vermibed will be 15,000 specimens per m2. The performance of this innovative biotreatment model (e.g. the quality of treated effluent and sludge as well as the LAB inoculum metabolic performance) will be tested under household conditions in the Republic of Moldova. If successful, the system may serve as a reliable technology for the bio-treatment of the house's effluents and sludge from the septic tanks that are commonly applied in rural and peri-urban areas of Moldova Country.

References
1. Andreev, N. 2017 Lactic acid fermentation of human excreta for
agricultural application, CRC Press, IHE Delft PhD Thesis Series, Balkema,
Leiden, The Netherlands ISBN 9781138049895
2. Alepu Odey, E. 2018 Optimization of latic acid fermentation for pathogen
inactivation in fecal sludge, Ecotoxicol Environ. Safety, 157, 249-254.
3. Krishnasamy,K., Jaya,N., Hughes R. Vermifiltration systems for liquid
waste management. J Environ Manage, 12, 2013, 382-396.

4. Lee,E. Yang H. Choi, J, Lee M., Park J. 2008. A study of sewage sludg
solubilizationby activity of lactic acid bacteria The 19th Annual
Conference of The Japan Society of Waste Management Experts, poster.
5. Singh, R., Bhunia, D Dash, R., 2017 A mechanistic review on
vermifiltration of wastewater, J Environ Manage, 197, 656-672.