PERANCANGAN ULANG DESAIN SEPTIC TANK BERDASARKAN PENGARUH PENAMBAHAN 6% BEKATUL TERHADAP PRODUKSI BIOGAS DAN EFISIENSI REMOVAL AIR LIMBAH PADA SEPTIC TANK DIGESTER (STUDI KASUS BULAKSUMUR RESIDENCE)

SOPHIA AN NISA, Dr. Ir. Sri Puji Saraswati, DIC., M.Sc

2015 | Skripsi | S1 TEKNIK SIPIL

Septic tank merupakan pilihan utama pengolahan limbah domestik bagi mayoritas masyarakat di Indonesia. Bangunan septic tank yang tidak didesain, dibangun dan dikelola dengan baik dapat mengakibatkan terjadinya luapan limbah. Masalah tersebut juga terjadi di Asrama Bulaksumur Residence sebagai pengguna septic tank. Keuntungan septic tank yaitu dapat digunakan sebagai digester untuk memanfaatkan hasil biogas. Namun, rasio C/N dari tinja manusia belum memenuhi syarat optimal produksi biogas, sehingga perlu ditambahkan substrat berkadar organik tinggi seperti bekatul. Tujuan dari penelitian yaitu mengetahui pengaruh penambahan 6% bekatul terhadap kuantitas dan kualitas produksi biogas serta limbah output model, mengetahui persentase removal limbah prototip dan model modifikasi septic tank serta pengusulan rancangan model septic tank. Penelitian berupa simulasi pemasukkan replika tinja ke dalam 2 model septic tank dengan dan tanpa penambahan 6% bekatul. Pengujian awal dilakukan pada prototip untuk mengetahui removal kualitas air limbah pH, TDS, EC, Nitrat, COD dan BOD5. Pengujian yang sama dilakukan pada model septic tank. Parameter uji kualitas dan kuantitas biogas yang dihasilkan pada model adalah CO2, CO, dan CH4 menggunakan gas chromatography. Persentase removal kualitas air limbah prototip berdasarkan parameter pH, TDS, EC, Nitrat, COD dan BOD5 berturut-turut sebesar 0,5%, -4,2%, -4%, -20,3%, -61,8% dan 8,5%. Persentase removal kualitas air limbah model tanpa penambahan bekatul berdasarkan parameter pH, TDS, EC, Nitrat, BOD5 dan COD berturut-turut sebesar -0,17%, 52,74%, 54,27%, 54,41%, 59,37% dan 83,2%. Persentase removal kualitas air limbah model dengan penambahan 6% bekatul berdasarkan parameter pH, TDS, EC, Nitrat, BOD5 dan COD berturut-turut sebesar 1,85%, 52,71%, 50,71%, 60,02%, 45,9% dan 78,05%. Nilai minus berarti kualitas memburuk, sedangkan nilai positif berarti kualitas limbah membaik. Persentase produksi biogas pada model dengan penambahan 6% bekatul menurut parameter CO2, CH4 dan CO memiliki nilai tertinggi berturut-turut yaitu 13,743%, 8,646% dan 14,668%. Pengujian removal dan kualitas air limbah menunjukkan bahwa model septic tank yang telah dimodifikasi memiliki kinerja yang lebih baik dari prototip sehingga diusulkan perbaikan desain prototip sesuai dengan desain model.

Septic tank is the first choice for domestical wastewater process in the majority of Indonesian community. Septic tank prototype which is not built, designed and operated in a proper way could cause sewage overflow. This problems occurs in Asrama Bulaksumur Residence as septic tank users. The advantage of septic tank is that it can be used as digester for biogas production usage. However, C/N ratio of human feces have not fulfulling the condition for optimal biogas production, therefore it will need some substrate which have high organic percentage such as bran. The purposes of this research are to know about the effect of 6% bran added to quality and quantity of biogas production and wastewater in output model, to know about removal percentage of wastewater from prototype and septic tank modification model, and to propose septic tank model design. This research process was a simulation of feces replica added into 2 septic tank models with and without 6% bran added. The first test was prototype removal for wastewater quality in pH, TDS, EC, Nitrat, COD dan BOD5. The quality and quantity of biogas are tested using chromatography gas. Removal percentage of wastewater quality in prototype based on pH, TDS, EC, Nitrat, COD and BOD5 in succession are 0,5%, -4,2%, -4%, -20,3%, -61,8% and 8,5%. Removal percentage of wastewater quality in model without 6% bran added based on pH, TDS, EC, Nitrat, COD and BOD5 in succession are -0,17%, 52,74%, 54,27%, 54,41%, 59,37% and 83,2%. Removal percentage of wastewater quality in model with 6% bran added based on pH, TDS, EC, Nitrat, COD and BOD5 in succession are 1,85%, 52,71%, 50,71%, 60,02%, 45,9% dan 78,05%. Minus value means that the quality is getting worse, positive value means that the quality is getting better. The highest biogas production percentage in model with 6% bran added based on CO2, CH4 and CO in succession are 13,743%, 8,646% and 14,668%. Removal and wastewater quality test showed that septic tank model which had been modificated has a better performance from prototype so it is suggested for prototype design to be repaired based on model design.

Kata Kunci : tinja, bekatul, biogas, removal, septic tank