**3. Methodology**

### **3.1 Site description**

The study was carried out at Lupane State University (18.9300<sup>0</sup> S, 27.7593°E) in Zimbabwe. This is a semi-arid area with annual rainfall of 550 mm, high summer and low winter temperatures. The university depends on septic tanks for sewage treatment. The design experiment followed a duplicate analysis setup with three treatments: septic tank effluent raw water (RW), vermifilter (VF) and a control (CF). Biofilters were designed and set up (two vermifilters and the control filter). Twentylitre plastic buckets measuring 27 cm x 29 cm x 32 cm were used as biofilter containers. Media consisted of four layers of 10–14 mm gravel, 4-8 mm gravel, river sand, black soil with *Eisenia festida* and 3 cm top layer. Layers were 4 cm, 4 cm, 10 cm, 20 cm and 3 cm thick, respectively. Twenty grams of earthworms per litre of black soil were used. The control biofilters did not have earthworms.

### **3.2 Measured parameters and method of measurement**

Total dissolved solids, pH, TSS, turbidity, BOD after 5 days, nitrates and phosphates and total coliforms (TCs) were measured using by the oven drying method, an electronic pH meter, Lovibond portable turbidity meter, BOD5 dilution method; Beckman Conlter UV/VIS Spectrum and Multiple Tube Fermentation Technique.

### **3.3 Data analysis**

Water quality parameter analysis was done before and after treatment. Genstat 14.0 was used for statistical analysis. The Shapiro–Wilk test (p < 0.05) was used to check for normality of data. One-way analysis of variance (ANOVA) at 5% level of

significance was used to test for significant differences in related parameters per treatment. Results were compared against the EMA standards (SI6 of 2007 on Effluent and Solid Waste Disposal).
